Ruthenium Cumulenylidene Complexes Bearing Heteroscorpionate Ligands
Rutheniumkumulenylidenkomplexe mit Heteroskorpionatliganden
Der Naturwissenschaftlichen Fakultät !der Friedrich-Alexander-Universität Erlangen-Nürnberg zur ! Erlangung des Doktorgrades Dr. rer. nat.
vorgelegt von
Frank Strinitz aus Nürnberg
Als Dissertation genehmigt von der Naturwissen-
schaftlichen Fakultät der Friedrich-Alexander-Universität
Erlangen-Nürnberg
Tag der mündlichen Prüfung: 02.12.2014
Vorsitzender des Promotionsorgans: Prof. Dr. Jörn Wilms
Gutachter: Prof. Dr. Nicolai Burzlaff
Prof. Dr. Rik Tykwinski
Die vorliegende Arbeit entstand in der Zeit von November 2011 bis August 2014 im Department für Chemie und Pharmazie (Lehrstuhl für Anorganische und Metallorganische Chemie) der Friedrich-Alexander-Universität Erlangen-Nürnberg unter der Anleitung von Prof. Dr. Nicolai Burzlaff.
Teile dieser Dissertation wurden bereits veröffentlicht:
„Ruthenium Carbonyl Complexes Bearing Bis(pyrazol-1-yl)carboxylato Ligands“, Türkoglu, G.; Tampier, S.; Strinitz, F.; Heinemann, F. W.; Hübner, E.; Burzlaff, N., Organometallics 2012, 31 (6), 2166-2174.
„Allenylidene Complexes Based on Pentacenequinone“, Strinitz, F.; Waterloo, A.; Tucher, J.; Hübner, E.; Tykwinski, R. R.; Burzlaff, N., Eur. J. Inorg. Chem. 2013, 5181-5186.
„Carbon-Rich Ruthenium Allenylidene Complexes Bearing Heteroscorpionate Ligands“, Strinitz, F.; Tucher, J.; Januszewski, J. A.; Waterloo, A. R.; Stegner, P.; Förtsch, S.; Hübner, E.; Tykwinski, R. R.; Burzlaff, N., Organometallics 2014, 33, 5129-5144.
Die schönsten Theorien werden durch die verdammten Versuche über den Haufen geworfen, es ist gar keine Freude mehr Chemiker zu sein.
-J. V. LIEBIG-
! ! Table of contents ! ! Table of Contents
1! Introduction ...... 1!
2! State of Knowledge ...... 3!
2.1! Carbonyl Complexes ...... 4! 2.2! Carbene Complexes ...... 8! 2.3! Vinylidene Complexes ...... 11! 2.4! Allenylidene Complexes ...... 15! 2.4.1! Neutral 16 Valence Electron Complexes ...... 18! 2.4.2! Cationic 18 Valence Electron Complexes ...... 21! 2.4.3! Neutral 18 Valence Electron Complexes ...... 27! 2.4.4! Reactions Involving Ruthenium Allenylidene Complexes as Precatalysts ...... 28! 2.5! Heteroscorpionate Chemistry ...... 29!
3! Objective and Aims ...... 35!
4! Results and Discussion ...... 37!
4.1! Manganese Based Photo-CORMs ...... 38! 4.2! Ruthenium Carbonyl Complexes Bearing Bis(pyrazol-1-yl)carboxylato Ligands ...... 44! 4.3! Ruthenium Heteroscorpionate Complexes with Aminophenol Based Ligands ...... 52! 4.4! Carbon-rich Ruthenium Allenylidene Complexes ...... 58! 4.4.1! Sterically Demanding Diphenyl Allenylidene Complexes ...... 59! 4.4.2! Fluorene Based Allenylidene Complexes ...... 66! 4.4.3! Anthraquinone Based Allenylidene Complexes ...... 74! 4.4.4! Pentacenequinone Based Allenylidene Complexes ...... 86! 4.4.5! Vinylidene Complex Bearing a Malonodinitrile Substituted Pentacenequinone ...... 97! 4.4.6! Benzotetraphenone Based Allenylidene Complexes ...... 101! 4.4.7! Larger Quinoidal Polyaromatic Compounds ...... 110!
4.4.8! Carbon-Rich Allenylidene Complexes Based on [RuCl2(PPh3)3] ...... 115! 4.5! Ruthenium Heteroscorpionate Cumulenylidene Complexes as Molecular Slides ...... 119! 4.5.1! Polyaromatic Ruthenium Vinylidene Complexes ...... 120! 4.5.2! Pyrene Based Allenylidene Complexes ...... 127! 4.5.3! Carbon-Rich Ruthenium Allenylidene Complexes Bearing the PTA Ligand ...... 135! 4.6! Arenium Cation or Radical Cation Pathway: Mechanistic Analysis and Experimental Proof of the Scholl Reaction of Pyrenophenone ...... 143!
5! Summary and Outlook ...... 147!
I ! ! Table of contents ! !
6! Zusammenfassung und Ausblick ...... 153!
7! Experimental Section ...... 161!
7.1! General Remarks ...... 162! Working Techniques ...... 162! 7.1.1! Chemicals !...... 162! 7.1.2! Instrumentation ...... 163! 7.1.3! CO-Release Studies ...... 164! 7.1.4! Cyclic Voltammetry ...... 164! 7.2! Synthesis of Compounds ...... 165! 7.2.1! Manganese Based Photo-CORMs ...... 165!
7.2.1.1! [Mn(bpzp)(CO)3] (4) ...... 165!
7.2.1.2! [Mn(HIm)3(CO)3]Br (6) ...... 165! 7.2.2! Ruthenium Carbonyl Complexes Bearing Heteroscorpionate Ligands ...... 166!
7.2.2.1! [Ru(bdmpza)H(CO)2] (11A/B) ...... 166!
7.2.2.2! [Ru(bdmpza)(CO)(μ2-CO)]2 (12) ...... 167!
7.2.2.3! [Ru(bpza)Cl(CO)2] (13) ...... 168! 7.2.3! Ruthenium Heteroscorpionate Complexes with Aminophenol Based Ligands ...... 169!
7.2.3.1! [Ru(bdmpza)Cl(IBQ)(PPh3)] or [Ru(bdmpza)Cl(ISQ)(PPh3)] (16) ...... 169! 7.2.4! Carbon-Rich Ruthenium Allenylidene Complexes ...... 170!
t 7.2.4.1! [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19A/19B) ...... 170!
7.2.4.2! [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B) ...... 171! 7.2.4.3! 10-Hydroxy-10-((trimethylsilyl)ethynyl)anthracen-9-one (23) ...... 173! 7.2.4.4! 10-Ethynyl-10-hydroxyanthracen-9-one (24) ...... 174!
7.2.4.5! [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B) ...... 175!
7.2.4.6! [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A/29B) ...... 176!
7.2.4.7! [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31) ...... 178! 7.2.4.8! 7-((Trimethylsilyl)ethynyl)-7H-benzo[no]tetraphen-7-ol (35) ...... 179! 7.2.4.9! 7-Ethynyl-7H-benzo[no]tetraphen-7-ol (36) ...... 180!
7.2.4.10! [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B) ...... 181! 7.2.4.11! Bisanthenequinone (39) ...... 183!
7.2.4.12! [RuCl2(═C═C═(FN))(PPh3)2] (45) ...... 184!
7.2.4.13! [RuCl2(═C═C═(AO))(PPh3)2] (46) ...... 185!
7.2.4.14! [RuCl2(═C═C═(PCO))(PPh3)2] (47) ...... 187! 7.2.5! Ruthenium Heteroscorpionate Cumulenylidene Complexes as Molecular Slides ...... 189!
7.2.5.1! [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48) ...... 189!
II ! ! Table of contents ! !
7.2.5.2! [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) ...... 190! 7.2.5.3! 1-Phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51) ...... 191!
7.2.5.4! [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B) ...... 192!
7.2.5.5! [Ru(bdmpza)Cl(PTA)(PPh3)] (55) ...... 193!
7.2.5.6! [Ru(bdmpza)Cl(PTA)2] (56) ...... 194! 7.2.5.7! [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B) ...... 195! 7.2.5.8! [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)] (58A/58B) ...... 196! 7.2.6! Intramolecular Scholl Reaction of Pyrenophenone ...... 198! 7.2.6.1! 6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-one (63); 11H-Indeno[2,1-a]pyren-11-one (64) .198!
8! Appendix ...... 201!
8.1! Details of the Structure Determinations ...... 202! 8.2! Cyclic Voltammetry ...... 211! 8.3! Myoglobin Assay of CORMs ...... 214! 8.4! List of Abbreviations and Symbols ...... 216! 8.5! List of Compounds ...... 219!
9! Bibliography ...... 221!
10! Danksagung ...... 241!
III
1 INTRODUCTION
1 ! ! Introduction ! !
In 1975 G. VIEHE et al. introduced the cumulogy principle as heuristicly important for the discovery of new substance classes.[1] They described on a series of organic molecules how the structure and reactivity correlates between common molecules and their cumulogous derivatives.
a) O C O O C C C O
(H C) N N(CH ) (H3C)2N N(CH3)2 3 2 3 2 b) C C C C (H3C)2N N(CH3)2 (H C) N N(CH ) 3 2 3 2
Scheme 1. Cumulogy principle by G. VIEHE et al.[1]
The principle was explained for several examples in organic chemistry as insertion of C2 fragments to obtain elongated molecules with comparable characteristics to the parent compound (Scheme 1). In the first report regarding this topic carbon dioxide was compared to tricarbon dioxide, which is surprisingly stable (Scheme 1-a) and the previously reported allenetetraamine to methanetetraamine (Scheme 1-b). The “vinylogy“ and „ethynylogy“ principles describe in a similar way the insertion of CH═CH and C≡C units between a few pairs of conjugated carbon atoms. A more complex approach towards an analogy principle is the carbo-mer principle which implies the insertion of Csp–Csp units into at least all symmetry- related bonds of a Lewis structure.[2-3]
While commonly applied in organic chemistry, the cumulogy principle can be extended to organometallic coordination chemistry. In their first report on allenylidene complexes in 1976
E. O. FISCHER et al. discussed the allenylidene moiety as cumulogous carbene ligand (Figure 1).[4] But also the metallacumulenes with even numbers of carbon atoms are accessible with the vinylidene complexes being the smallest of this series.
R R
[MLn] (C)n C [MLn] (C)n C C R R
n = 0, 2, 4, etc.
Figure 1. Principle of uneven and even metallacumulenes.
2
2 STATE OF KNOWLEDGE
3 ! ! State of Knowledge ! !
In the following chapter a brief overview over the most common carbon based ligands namely carbonyl, carbene, vinylidene and allenylidene ligands will be given with focus on their syntheses, properties and possible applications.
2.1 Carbonyl Complexes
In the early 19th century J. V. LIEBIG synthesized a compound he named “Kohlenoxidkalium” which may be translated as “potassium carbon oxide” and was initially expected to be the carbonyl complex with the formula KCO.[5-6] In 1885 R. NIETSKI and T. BENCKISER identified this compound as potassium salt of hexahydroxybenzene due to its similar reactivity after hydrolysis.[7] But it was not until the sixties of the last century that the final verdict was spoken on this compound. E. WEISS et al. revealed with an X-ray crystal structure analysis the formation of potassium acetylenediolate KOC≡COK which can undergo hydrolysis or thermolysis to form potassium hexahydroxybenzene.[8-9] The first real transition metal carbonyl complex that survived later investigations was reported in 1868 by M. P.
SCHÜTZENBERGER as he published dicarbonyl dichloroplatinum [Pt(CO)2Cl2] along with [10-11] [Pt2(CO)Cl4] and [Pt2(CO)3Cl4].
However, carbonyl chemistry first arouse significant interest with the development of the
[12-13] Mond Process in 1890 which allowed purification of nickel via the volatile [Ni(CO)4]. Starting from this observation the synthesis of homoleptic complexes i.e. carbonyl complexes only with carbonyl ligands and heteroleptic complexes with additional ligands were extensively studied.
Especially, for the neutral binary metal carbonyls a strong influence of the group in the periodic table can be observed. To achieve the formal 18 valence electrons (VEs) group 7 and 9 metal carbonyls are forced to dimerize or to form even larger clusters (Table 1). Common features are the high hydrophobicity, which leads to good solubility in organic solvents like acetone or hexanes. Depending on their geometry a variety of air-stable or pyrophoric complexes are reported. Moreover, the volatility of complexes like [Ni(CO)4] or [Fe(CO)5] leads to high toxicity. The variety of transition metal complexes is extensively discussed in literature and will not be further discussed within this thesis.[14-15]
4 ! ! State of Knowledge ! !
Group
5 6 7 8 9 10
[Fe(CO)5] [Co2(CO)8]
[V(CO)6] [Cr(CO)6] [Mn2(CO)10] [Fe2(CO)9] [Co4(CO)12] [Ni(CO)4]
[Fe3(CO)12] [Co6(CO)16]
[Ru(CO)5] [Rh2(CO)8] [Tc2(CO)10] [Mo(CO)6] [Ru3(CO)12] [Rh4(CO)12] [Tc3(CO)12] [Ru6(CO)18] [Rh6(CO)16]
[Os(CO)5] [Ir4(CO)12] [W(CO)6] [Re2(CO)10] [Os3(CO)12] [Ir6(CO)16]
Table 1. Neutral binary carbonyl complexes of the transition metals.[16]
The Dewar-Chatt-Duncanson Bonding Model is employed to describe the bond properties between metal atoms of the d-block and carbon monoxide, which describes the bonding as donor-acceptor-interaction with a σ donor (forward donation) and π acceptor (back donation).[16]
The mainly carbon centered 5σ orbital of the carbonyl ligand interacts as highest occupied molecular orbital (HOMO) under formation of a σ bond with an empty d or p orbital of the metal center and transferring electron density towards the center (Figure 2-a).[16] To maintain the principle of electroneutrality a π backbond is formed from the highest occupied atomic orbital (HOAO) of the metal atom and the 2π* orbital (LUMO) of the carbonyl ligand (Figure 2-b). Thus the π backbond shifts electron density into the antibonding 2π* orbital in the carbonyl ligand (Figure 2-c), which leads to a lower bond strength and in consequence to a
2 lower CO force constant in comparison to gaseous carbon monoxide (kCO = 18.6 × 10 Nm–1).[17] This holds true for most known metal carbonyls indicating that the π backbond is the dominating part of the M-CO bonding energy. Nevertheless, for positively charged metal carbonyl complexes larger CO force constants can be observed, which backs the conclusion that the π backbond is in these cases inferior to the σ forward bond.[16]
5 ! ! State of Knowledge ! !
a) b) c)
O C M O C M O C M
Figure 2. Bonding in carbonyl complexes.[16]
These sensitive parameters make carbonyl complex precursors useful for modern organometallic chemistry as they lead to complexes with easily comparable parameters that support conclusions on the bond strength of carbonyls and thus the carbonyl vibrations.
CO Releasing Molecules (CORMs)
In recent years, the therapeutic potential of carbon monoxide has attracted a lot of attention despite the general high toxicity to humans due to interaction of this odorless and colorless gas with heme proteins. The biological importance of the closely related isoelectronic nitrogen monoxide has been underlined already in 1992 by Science as “The Molecule of the
Year”.[18] R. TENHUNEN and R. SCHMID identified in 1968 that heme oxygenase (HO) enzymes are ubiquitous in nature and evolutionary conserved.[19] HO catalyzes the heme oxidation at the α position of the protoporphyrin ring leading to the formation of biliverdin and an endogenous production of one equivalent CO at a rate of a few milliliters per day (Scheme 2).[20]
CH CH2 2 Me Me
Me Me N N CH2 NH N CH2 Fe heme oxygenase O 2+ O N N - CO, Fe NH HN Me Me Me Me
HOOC COOH HOOC COOH
Scheme 2. Heme degradation catalyzed by heme oxygenase and the resulting oxidation product biliverdin.[20]
6 ! ! State of Knowledge ! !
Furthermore, it participates in the reaction as both prosthetic group and substrate, while O2 and NADPH are required as cofactors.[21] In the next step the biliverdin reductase reduces the intermediary species to bilirubin.[19] This endogenously produced CO acts as a small-molecule messenger (gasotransmitter), like hydrogen sulfide or nitric oxide.[22-24] In most cases the interaction of CO is focused on heme-containing metalloproteins. Vasodilation can be induced by binding of CO to soluble guanylate cyclase (sGC) and to heme groups inside the
2+ [25] network of large conductance Ca -activated potassium channels (BKCa). Some other pharmacological activities include anti-inflammatory, anti-hypertensive and anti-ischemic effects.[26-28]
The difficulties in handling and dosing a highly toxic gas like carbon monoxide lead to the development of solid storage forms like Carbon Monoxide Releasing Molecules (CORMs), which allow the generation of CO at constant low concentrations in proximity to the pharmacological target.[29-31] The first generation of CORMs consists of CORM-1
(dimanganese decacarbonyl, Mn2(CO)10) and CORM-2 (tricarbonyldichloro-ruthenium(II) dimer, [RuCl2(CO)3]2) (Figure 3), which are only soluble in organic solvents but show carbon monoxide release in biological environments under appropriate conditions.[32]
O O O C O C C CO C Cl OC Cl CO OC Mn Mn CO Ru Ru OC Cl CO C C C O Cl C O O C O O
Figure 3. CORM-1 (dimanganese decacarbonyl) and CORM-2 (tricarbonyldichloro-ruthenium(II) dimer).[32]
For CORM-1, an external light trigger is required to induce CO-release while for CORM-2, the presence of myoglobin (Mb) leads to ligand dissociation and formation of MbCO. To overcome the poor solubility in aqueous media, CORM-3 (tricarbonylchloro(glycinato)- ruthenium(II)) was designed by R. MOTTERLINI et al. and is so far the most commonly employed CORM in biological studies.[27] More recently, CORM-F7 (η5-4-(4-chloro-2- pyrone)tricarbonyliron(0)) and CORM-F10 (carbonyl pyrone molybdenum complex) have also received considerable attention.[33-35] In these complexes, the CO-release is triggered by ligand exchange in aqueous media. As an alternative, the functionalization of CORM-1 to yield manganese-based PhotoCORMs has received a lot of attention, lately. For example,
+ [Mn(CO)3(tpm)] releases CO upon activation with UV light, leading to a cytotoxic activity
7 ! ! State of Knowledge ! ! against cancer cells, but remaining inactive even after prolonged exposure in the dark.[36] Additionally, bioconjugates of this lead compound led to improved drug delivery. Therefore, peptides and SiO2 particles as well as carbon nanomaterials functionalized with azide moieties + were connected via Click Chemistry with the alkyne substituted [Mn(CO)3(tpm)] fragment.[37-39] Nevertheless, due to a Tolman cone angle close to 180° for Tp (Tp = hydridotris(pyrazol-1-yl)borate), the exchange of more than one carbonyl during synthesis is hindered in the case of tricarbonyl Tp complexes.[40-41] As an alternative ligand system, less bulky heteroscorpionate ligands have been established such as Hbpza (bis(pyrazolyl)acetic acid), in which one pyrazole has been substituted by a carboxylate group.[42-43] From a synthetic point of view, the closely related class of bis(pyrazolyl)methane- carboxylates (bpmc) has been explored, too.[44]
2.2 Carbene Complexes
In comparison to the aforementioned carbonyl complexes a transition metal carbene complex is an organometallic compound featuring a divalent organic ligand that is most commonly described as metal carbon double bond. The classical carbene complex synthesized by E. O.
FISCHER et al. in 1964 was the starting point for the following metathesis catalysts.[45] The conversion of W(CO)6 with phenyllithium and subsequent methylation with diazomethane yielded the first tungsten methoxymethylcarbene complex (Scheme 3).
O + OMe (OC)5W C Me4N Ph (OC)5W C Ph 1. H+ 1. PhLi CO 2. CH2N2 or + O OMe OC CO 2. Me4N + [(CH3)3OBF4] W (OC)5W C Me4N (OC)5W C OC CO Ph Ph CO
OMe (OC)5W C Ph Scheme 3. Synthesis of the classical Fischer Carbene Complex.[45]
8 ! ! State of Knowledge ! !
The class of Fischer Carbene Complexes is composed of middle to late transition metals in low oxidation states with the carbene ligand stabilized by heteroatoms with a positive mesomeric effect like oxygen. These electron rich complexes are usually bearing additional carbonyl ligands to transfer electron density via π backbonding towards the LUMO of the carbonyl.[46]
The bond between the metal fragment and the carbene ligand is based on a σ-bond between the double occupied sp2 hybridized orbital of the singlet carbene and an empty d-orbital of the metal center (Figure 4-a). Additional stabilization results from a π backbond from a double occupied d-orbital into the unoccupied pz-carbene orbital (Figure 4-b). Further stabilization of this unoccupied orbital can be achieved via conjugation with the free electron pair of the neighboring heteroatom (Figure 4-c).[46]
a) b) c)
OR OR O R M C M C C R´ R´ R´
Figure 4. Bonding in Fischer Carbene Complexes.
The use of electron donating heteroatoms and carbonyl ligands as electron density acceptors leads to a less pronounced metal to carbene backbonding. As consequence of this reduced bond order between ligand and center a higher bond order between carbon and neighboring heteroatom can be observed. This electron distribution explains the reactivity of Fischer
Carbene Complexes, which are classified by their electrophilicity on the Cα carbon atom.
On the contrary the nucleophilic carbene complexes developed by R. R. SCHROCK were first published in 1974. The attempt to coordinate five neopentyl ligands to a tantalum center led
[47] to the intermolecular deprotonation of one Cα carbon atom forming the carbene complex.
9 Kenntnisstand
Aufgrund der zuvor bereits erwähnten Verwendung von Carbonylen als -Akzeptoren kommt es zu einer vergleichsweise geringen Ausprägung der Metall-Carben- Rückbindung. Dies bedeutet eine Verringerung der Bindungsordnung zwischen Ligand und Zentrum, führt jedoch gleichzeitig zu einer Erhöhung der Bindungsordnung zwi- schen Kohlenstoff und benachbartem Heteroatom (Abb. 5). Die Reaktivität der Fi- scher-Carbene ist vor allem durch ihre Elektrophilie geprägt.
Abb. 5: Elektronische Struktur der Fischer-Carbenen.
Schrock et al. hingegen synthetisierten 1974 den ersten nukleophilen Carbenkomplex durch Deprotonierung eines -Kohlenstoffatoms an einem Tantalalkylkomplex.[4] Bei dem Versuch fünf Neopentylliganden an einem Tantalzentrum zu koordinieren, kam es zu dieser „unerwarteten“ Reaktion. Die Zugabe von Neopentyllithium führte zur Koor- dination eines vierten Liganden, der fünfte jedoch fungierte als Base und führte zur ! ! Bildung des Tantal-Alkyliden-KomplexesState (Abb.of Knowledge 6). ! !
Abb. 6: Synthese des Tantal-basierten Schrock-Carbens.[4] Scheme 4. Synthesis of the tantalum based Schrock Carbene Complex.[47]
BeiThe Schrock class of -SchrockCarbenen Carbenes handelt is composed es sich imof early Allgemeinen transition ummetals Komplexe in high oxidation früher Übestatesr- gangsmbearing etalle stabilizing in hoher π-donor Oxidationsstufe, ligands to overcome die durch the reduced-Donorliganden electron densitystabilisiert at the werden. center. EinThese weiterer changes charakteristischer result in the characteristic Unterschied tri pletist der state Triplettzustand of the carbene des ligand Carbens (Figure (Abb. 5-a). Overall these modifications lead to a significantly enhanced π backbond between the metal 7-I). Insgesamt führen diese Unterschiede vor allem zu einer signifikant stärkeren - center and the carbene ligand. On the one hand this behavior explains the strong double bond Rückbindung zwischen Metallzentrum und Carben, was sich einerseits durch einen character and on the other hand the nucleophilicity of the system (Figure 5-b). deutlichen Doppelbindungscharakter äußert, andererseits die Nukleophilie des Sys- tems erklärt (Abb. 7-II). a) b) R´ R´ R´ M + C MLn C MLn C R R R 3
Figure 5. Bonding in Schrock Carbene Complexes.
Based on these results, R. R. SCHROCK[48] and R. GRUBBS[49] developed their famous
metathesis catalysts which were awarded with the Nobel Price in 2005 and included Y.
CHAUVIN for the suggested mechanism.[50-52]
Grubbs I Catalyst Schrock Catalyst
P(Cy)3 Cl F3C N Ru F3C O Mo Cl Ph O Ph P(Cy)3
CF3 CF3
Figure 6. Structure of the first generation Grubbs Catalyst and the Schrock Catalyst.[48-49]
The two classic metathesis catalysts by R. GRUBBS and R. SCHROCK are depicted in Figure 6. Today a wide variety of catalyst systems are known that can be employed depending on the
10 ! ! State of Knowledge ! ! desired substrate. This topic has been intensively reviewed within the last years. This also explains the importance of the metathesis reaction especially for pharmaceutical applications and green chemistry.
Due to the simplicity of the mechanism behind the catalytic olefinic metathesis, which was once described by R. SAALFRANK as consolidated enough to fit on a beer coaster, a brief description will be given (Scheme 5).[53] Starting from the carbene catalyst a formal [2+2] cycloaddition of an alkene leads to a metallacyclobutane intermediate. This compound can either undergo cycloreversion to the starting compounds or proceed towards a new carbene complex and alkene. The entire reaction is per se reversible but driving forces behind the conversion like reduced ring strain, increase in entropy and removal of gaseous compounds (in the depicted case ethylene) direct the equilibrium towards the product.[52]
H R1 H R1 H [M] C C C C C H H R2 H H
H H H C [M] [M] C H R2 C C C C H R1 R1 H H H H
H H H H C [M] C C C 2 R1 H H R H H
Scheme 5. Basic mechanism of metathesis reactions as described by Y. Chauvin.[52]
2.3 Vinylidene Complexes
Vinylidene H2C═C: is the simplest unsaturated carbene and is tautomeric to acetylene HC≡CH.[54] The organic chemistry of unsaturated carbenes has been summarized by P.
STANG.[55-56] Regarding vinylidenes from an organometallic point of view, the first synthesis of a molybdenum based vinylidene complex was reported by M. SARAN and R. KING in
[57] 1972. The reaction of a 1-chloro-2,2-dicyanovinylmolybdenum complex with PPh3 leads to
11 ! ! State of Knowledge ! ! carbonyl-free vinylidene complex under migration of the chloride anion towards the molybdenum center (Scheme 6).
PPh3,Δ Mo n-octane Mo OC CO Ph3P Cl Cl C OC Ph3P CN NC CN NC
Scheme 6. Synthesis of the first vinylidene complex based on molybdenum.[57]
In analogy to carbene complexes vinylidene complexes can be described as extended cumulene. The bonding in vinylidene complexes takes place in a similar fashion as it consists of a σ bond and a π backbond, which results in an electrophile Cα atom and a nucleophilic Cβ position. The preparation of vinylidene complexes is quite versatile although four major synthetic routes have been established. The direct transformation of 1-alkynes via a 1,2- hydrogen shift, the addition of electrophiles to metal alkyne complexes, the deprotonation of carbyne complexes and the formal dehydration of acyl complexes will be briefly discussed.
1,2-Hydrogen Shift
The 1,2-hydrogen shift is due to its simplicity a useful access into vinylidene complex chemistry (Scheme 7-a). After side-on coordination of the alkyne the rearrangement precedes by an η2- to η1-alkyne slippage. The relative stability of the vinylidene complex in comparison to the intermediary alkyne complex increases with electron density on the ruthenium center. This allows for several ruthenium systems depending on the ligands employed the isolation and characterization of the vinylidene complex as well as the alkyne complex. First reports on the formation of Cp based ruthenium vinylidene complexes were published in 1989 by R. BULLOCK.[58] M. BRUCE et al. reported extensively on the transformation of [RuCp*Cl(PPh3)2] with a series of 1-alkynes to neutral vinylidene [59-60] complexes (Scheme 7-b). The initial reaction step was the displacement of one PPh3 ligand followed by the 1,2-H shift described above. Similar results were obtained by N.
BURZLAFF et al. with the bdmpza (bis-(3,5-dimethylpyrazol-1-yl)acetato) based complex
[61] [Ru(bdmpza)Cl(PPh3)2] that also allows the formation of neutral vinylidene complexes. Due to the N,N,O binding motif the formation of two structural isomers can be observed with
12 ! ! State of Knowledge ! ! the vinylidene unit being either positioned trans to the pyrazole unit or the carboxylate anchor and the PPh3 ligand remaining trans to the pyrazole moiety.
a) H H H 1,2-H-shift LnM C MLn C C ML C n R R R
b)
HC CR Ru Ru Ph3P benzene, Δ Ph3P C H Cl PPh3 Cl C R
t R = Me, Et, Pr, Bu
Scheme 7. a) Mechanism of the 1,2-hydrogen shift; b) synthesis of a ruthenium based Cp* vinylidene complex.[58]
Metal Acetylides
R
[Ru] Cl + H C C R – [Ru] C C - Cl H
H+ NaOMe
R R X C H + [Ru] C C 2 [Ru] C C R 7 7 [Ru] C C X
5 ArN + [Ru] = Ru(PPh3)2(η -C5H5) 2 R = Me, tBu, Ph, etc. i R´= Me, Pr, CH2Ph, etc. R Ar = Ph, Xyl, etc. [Ru] C C X = Cl, Br, I N N Ar
Scheme 8. Preparation of ruthenium vinylidene complexes via electrophile addition.[62-65]
13 ! ! State of Knowledge ! !
The coordination of an acetylide anion to a metal center results in a transfer of electron density to Cα and in consequence in a shift of nucleophilicity from Cα to Cβ. The addition of electrophiles to the electron rich Cβ has been described extensively and is the best entry into vinylidene complex chemistry, if no proton on Cβ is required. A large amount of substituted vinylidene complexes is achievable by switching electrophiles. Known in literature are reversible protonation, alkylation, halogenation, diazotization and insertion of further functional groups (Scheme 8).[62-65]
Deprotonation of Carbyne Complexes
Deprotonation of carbyne complexes bearing protons at the Cβ atom allows the isolation of an anionic vinylidene complex. A. ORPEN et al. reported for the system [MoCp(CCHtBu)-
(P(OMe)3)2] the deprotonation with n-BuLi which led to the anionic molybdenum complex which can either be described with the charge located on the ligand or the metal center describing a vinylidene complex (Scheme 9).[66] This route to vinylidene complexes is usually limited to the earlier transition metals.[67-70]
n-BuLi Mo Mo Mo (MeO)3P THF (MeO)3P (MeO)3P C C C t (MeO)3P t (MeO)3P t (MeO)3P CH Bu CH2 Bu CH Bu Li Li
Scheme 9. Synthesis of a molybdenum vinylidene complex starting from a carbyne complex.[66]
Acyl Complexes
A fourth pathway towards vinylidene complexes starts from acyl complexes and was first described by B. BOLAND-LUSSIER and R. HUGHES.[71] J. GLADYSZ et al. reported a similar approach starting from a rhenium based acyl complex which required a stepwise addition of
t (CF3SO2)2O and KO Bu followed by (CF3SO2)2O (Scheme 10). Further cycles of base and acid addition allowed the reversible reaction between vinylidene and acetylide complex.[72-73]
14 ! ! State of Knowledge ! !
1. 0.5 eq. (CF3SO2)2O 2. KOtBu Re 3. 0.5 eq. (CF3SO2)2O Re ON PPh3 ON PPh3 C C O C R R H
R = H, Me, Ph t CF3SO3H BuOK
Re ON PPh3 C C R
Scheme 10. Dehydroxylation of an acyl complex to the corresponding vinylidene or acetylide complex.[72-73]
2.4 Allenylidene Complexes
The first reports on allenylidene complexes were published in 1976 independently by H.
[4, 74] BERKE and E. O. FISCHER et al. Previously only the free labile allenylidene (:C═C═CH2) could be trapped in a matrix.[75] Similar to the vinylidene complexes several routes are known to allenylidene complexes, which have been extensively reviewed.[76-82] Hence, only the most common routes will be discussed within this work. For group 6 metals the method employed by E. O. FISCHER et al. starts from an alkenylalkoxycarbene complex. The stepwise conversion with a Lewis acid and THF as base led under 1,2-elimination of ethanol to the allenylidene complex (Scheme 11).[4]
15 ! ! State of Knowledge ! !
OC H 2 5 1. EX3/CH2Cl2 Ph (CO) M C Ph 2. THF 5 (CO) M C C C HC 5 - C2H5OH N(CH3)2 N(CH3)2 M = Cr, EX3 = BF3 M = W, EX3 = Al(C2H5)3
Scheme 11. Synthesis of the first allenylidene complex by E. O. FISCHER et al.[4]
This route allows the formation of mono-heteroatom substituted allenylidene complexes but a different approach is required for di-heteroatom substitution patterns. H. FISCHER et al. established a route starting from [(CO)5M(THF)] (M = Cr, W), which yields upon addition of deprotonated 3,3,3-tris(dimethylamino)prop-1-yne the intermediary metalate (Scheme 12).[83]
The abstraction of one amino group with BF3 etherate directly afforded the corresponding neutral allenylidene complex. This route has also been employed on the synthesis of the cumulogous pentatetraenylidene complex.[83]
[(CO)5M(THF)] + C C C(NMe2)3 M(CO)5 C C C(NMe2)3
. NMe2 BF3 OEt2 [(CO)5M] C C C M = W, Cr NMe 2
Scheme 12. Synthesis of di-heteroatom substituted allenylidene complexes via alkynyl metalates.[83]
The current popularity of ruthenium allenylidene complexes can also be attributed to the discovery of J. SELEGUE in 1982, that the direct conversion of [RuCpCl(PMe3)2] with 1,1- diphenylprop-2-yn-1-ol led to a cationic allenylidene complex (Scheme 13).[84] This method is based on the spontaneous dehydration of propargyl alcohols after η2-coordination of the alkyne to 16 VE complexes that form intermediary hydroxyl vinylidene complexes.[84]
16 ! ! State of Knowledge ! !
OH Ru Me3P Ru + H C C C Ph - C - H2O, Cl Me P C Ph Ph 3 C Me3P Cl PMe3 Ph
- Cl- - H2O
Me P Ru Ru 3 C Me3P CH Me3P PMe3 OH Ph Ph OH H C C C Ph Ph
Scheme 13. Synthesis of the first allenylidene complex based on a propargyl alcohol by J. SELEGUE and the mechanism of the dehydration.[84]
This method has proven to be suitable for a wide variety of ruthenium systems although certain limitations are known. For a successful transformation i) the metal precursor needs to form a coordinatively unsaturated 16 VE complex that allows η2-coordination of the alkyne. The next limitation ii) is oftentimes the reluctance of the 3-hydroxyvinylidene to undergo dehydration (Scheme 14-a). This behavior is especially distinctive when electron-rich metal fragments are used. Depending on the used propargyl alcohol also iii) the competitive formation of alkenylvinylidene complexes can occur, if the Cδ is carrying protons and thus allows an 3,4-elimination of water with respect to the ruthenium center.[85-88] In some cases the high stability of 3-hydroxyvinylidenes requires the treatment with acidic Al2O3 to complete the conversion towards the allenylidene complex.[89-90] Calculations on the half-sandwich
+ system [RuCp(PH3)2] have emphasized the importance of protic solvents (e.g. MeOH) for the transformation of the propargyl alcohol to the allenylidene complex (Scheme 14-b).[91]
17 ! ! State of Knowledge ! !
H R2 = CHR3R4 [M] C C R3 - H O 2 C C 1 4 OH H R R H C C C [M] C C OH 2 R C R1 R1 R2 R2 [M] C C C - H O 2 R1
Me O Me H H O H Me O H H O O H H [Ru] C C H [Ru] C C C [Ru] C C C H H C O H H H H H
Scheme 14. a) Synthesis of allenylidene and alkenylvinylidene complexes via 3-hydroxyvinylidene intermediate; b) Mechanism of methanol catalyzed allenylidene formation.
The different ruthenium allenylidene complexes can be divided into three different groups, namely neutral 16 VE complexes, cationic 18 VE complexes and neutral 18 VE complexes.
2.4.1 Neutral 16 Valence Electron Complexes
Starting from [RuCl2(PPh3)3] and [RuCl2(PPh3)4] A. HILL and P. NOLAN independently explored the reaction with the propargyl alcohol 1,1-diphenylprop-2-yn-1-ol which led to the complex [RuCl2(═C═C═CPh2)(PPh3)2] or upon addition of PCy3 to the complex to [92-95] [RuCl2(═C═C═CPh2)(PCy3)2], which is closely related to Grubbs first generation catalyst
[RuCl2(═CHPh)(PCy3)2]. Nevertheless, the synthesis of [RuCl2(═C═C═CPh2)(PPh3)2] has shown to be strongly temperature dependent as high temperatures allow the selective formation of this 16 VE complex. Lower temperatures and the addition of NaPF6 led to the additional formation of two 18 VE complexes that can be explained as dimeric forms of the parent 16 VE complex. To compensate the lack in electron density either strongly donating solvents are reported in the crystal structures of the complexes ([RuCl2(═C═C═CPh2)-
18 ! ! State of Knowledge ! !
(PPh3)2(solvent)] (solvent = H2O, MeOH, EtOH) or the formation of a symmetric or asymmetric unit can be observed (Scheme 15).[96]
Cl PPh Ph HC C C(Ph)2OH 3 [RuCl (PPh ) ] Ru C C C 2 3 3 toluene, Δ, 4 h Ph3P Cl Ph
HC C C(Ph)2OH THF for X = Cl NaPF6 25 °C THF 2h Δ
X
CPh2 Cl PPh3 C Ph3P Cl Ph2C C C Ru Cl PPh3 C Ph3P Ru Ru Ph3P Cl Ru C C CPh2 Cl PPh3 Cl C PPh3 Ph3P Cl C X = Cl, PF6 Ph2C
Scheme 15. Synthesis of monomeric, neutral dimeric and cationic dimeric diphenyl allenylidene complexes [96] based on [RuCl2(PPh3)3].
For the dimeric species two AB quartet patterns can be observed in the 31P NMR spectrum, which can be assigned to the two different dimers (Scheme 15). Based on spectroscopic analysis, one of the dimers contains two bridging and two terminal chlorido ligands, leading to a neutral 18 VE complex. The second dimer is a monocationic complex that contains three bridging chlorido ligands. The positive charge is compensated by a chloride anion that is released during dimerization but can also be exchanged by addition of NaPF6 allowing to shift the equilibrium towards the cationic dimer.
The monomeric allenylidene complex [RuCl2(═C═C═CPh2)(PPh3)2] can also be used as a precursor for the selective formation of 18 VE complexes. Addition of dppe (1,2- bis(diphenylphosphino)ethane) and KPF6 leads to the cationic complex [RuCl(═C═C═CPh2)-
(dppe)2]PF6 while the addition of carbon monoxide leads to the formation of [93] [RuCl2(═C═C═CPh2)(CO)(PPh3)2].
The chemistry of the tricyclohexylphosphine-based complex [RuCl2(═C═C═CPh2)(PCy3)2] is even more versatile as it allows a series of conversions. Reaction with the potassium salt of
19 ! ! State of Knowledge ! ! the hydridotris(1-pyrazolyl)borate ligand leads to the formation of the neutral 18 VE complex
[93] 6 i [Ru(HB(pz)3)Cl(═C═C═CPh2)(PPh3)]. Addition of the dimeric [Ru2Cl4(η -MeC6H4 Pr)2] 6 i leads to the formation of the dimer [Ru2Cl4(═C═C═CPh2)(PCy3)(η -MeC6H4 Pr)] which in this case shows two bridging chlorido ligands with two terminal chlorido ligands, thus resulting in a neutral complex (Scheme 16).[92] In comparison the conversion of the allenylidene complex with the N-heterocyclic carbene ligand 1,3-bis((2,6-di-isopropyl- phenyl)imidazol-2-ylidene) (IPr) leads to the 16 VE complex [RuCl2(═C═C═CPh2)-
(PCy3)(IPr)], which undergoes rearrangement to the indenylidene complex [RuCl2(3- [94] phenylindenylid-1-ene)(PCy3)(IPr)].
Several of the aforementioned complexes have been tested as precatalysts in metathesis reactions and this topic will be discussed later within this work (2.4.4, page 28).
[Ru Cl (MeC H iPr) ] Cl Cl 2 4 6 4 2 Ru Ru Cl Cl C PCy3 C CPh2 Cl PCy3 Ru C C CPh2 Cy3P Cl Cl IPr Cl IPr Ph IPr Ru C C CPh2 Ru C Cy3P Cl Cy3P Cl
IPr = N N
i Scheme 16. Synthesis of [Ru2Cl4(═C═C═CPh2)(PCy3)(η-MeC6H4 Pr)], [RuCl2(═C═C═CPh2)(PCy3)(IPr)] and [92, 94] [RuCl2(3-phenylindenylid-1-ene)(PCy3)(IPr)] starting from[RuCl2(═C═C═CPh2)(PCy3)2].
20 ! ! State of Knowledge ! !
2.4.2 Cationic 18 Valence Electron Complexes
The group of cationic 18 VE ruthenium allenylidene complexes can be divided into the group of complexes based on ligands with heteroatoms coordinating in κ1- to κ4-mode and the group of η5- and η6-arene complexes. As mentioned previously for the 16 VE complexes many of
1 the complexes based on κ -coordinating ligands like PPh3 and PCy3 tend to form 18 VE complexes via addition of Lewis bases.[93, 96] Ruthenium allenylidene complexes bearing κ2- coordinating ligands are usually based on the diphosphine ligands dppm (1,2- bis(diphenylphosphino)methane) and dppe (1,2-bis(diphenylphosphino)ethane). Starting from cis-[RuCl2(dppm)2] a variety of cationic ruthenium allenylidene complexes of the general [82] formula trans-[RuCl(═C═C═CHR)(dppm)2]PF6 has been synthesized. Especially remarkable is the stabilization of monosubstituted allenylidene complexes starting from secondary propargyl alcohols as usually the formation of α,β-unsaturated and polyenyl carbenes via reactive γ-monosubstituted allenylidenes occurs (Scheme 17).[97-99] It is assumed
+ that the system [RuCl(dppm)2] shows larger electron releasing properties than comparable cationic arene based systems and thus a decrease of the electron deficiency of the
+ [Ru═C═C═CHR] moiety and especially of the Cα carbon atom occurs.
PF6 PPh2 Ph P 2 PPh2 H Ph2P Cl NaPF Ru 6 Cl Ru C C C Ph2P Cl H C C CHR(OH) R PPh Ph2P PPh2 2 R = Ph, p-PhCl, p-PhF, p-PhOMe
Scheme 17. Synthesis of stable monosubstituted allenylidene complexes bearing dppm ligands.[82]
Following this initial work, based on the dppm ligand, the complexes based on the dppe system led to even more stable systems as indicated by the in situ generation of
[100-101] [RuCl(dppe)2]PF6 from cis-[RuCl2(dppe)2] upon addition of NaPF6. This system has proven to be quite versatile and allows on the one hand systems similar to the dppm based allenylidene complexes bearing a chlorido ligand trans to the allenylidene unit.[102] On the other hand, highly unsaturated alkynyl allenylidene ruthenium complexes are achievable (Scheme 18),[102] which are especially interesting due to their potential to create a C–C bond,
21 ! ! State of Knowledge ! ! by carbon-rich ligand coupling.[103-105] In addition, their dual alkynyl donor and allenylidene acceptor functionalities raise interest in building linear conjugated organometallics.[102]
PF6 PF6 Ph2P PPh2 1 2 Ph2P PPh2 H HC C CR R OH, R1 Cl Ru C C NaPF6, Et3N R C C Ru C C C R R2 CH2Cl2 Ph2P PPh2 Ph2P PPh2
R = H; R1 = R2 = Ph R = nBu; R1 = R2 = Ph R = Ph; R1 = R2 = Ph etc.
Scheme 18. Synthesis of highly unsaturated alkynyl allenylidene complexes via deprotonation of allenylidene [102] complexes based on trans-[RuCl(═C═CHR)dppe2]PF6.
It is noteworthy that these mixed alkynyl allenylidene complexes are stable towards the
[106-107] addition of methanol at Cα and Cγ in contrast to other systems. The steric hindrance and the strong electron donating capabilities of the dppe ligands reduce the reactivity allowing only stronger nucleophiles like sodium methoxide to react selectively with the Cγ carbon atom resulting in ruthenium diacetylide complexes.[102, 108-109] Starting from the mixed alkynyl allenylidene complex trans-[Ph2C═C═C═(dppe)2Ru—C≡C―CHPh]PF6, the oxidation with Ce(IV) ammonium nitrate allows the isolation of the first real bis(allenylidene) metal complex (Scheme 19). The previously reported bis(allenylidene) complex trans-[(dppm)2Ru- 2+ (═C═C═C(OMe)(CH═CPh2))2] shows due to the presence of a donor group on the unsaturated chain an elevated bis(alkynyl) character and can better be described as trans-
2+ [110-112] (dppm)2Ru[—C≡C—C(═OMe)(C═CPh2)]2 . Especially interesting is the behavior upon one electron reduction due to the formation of a stable radical complex with an electron pair delocalized identically on both sides of the alkynyl allenylidene complex. This observation shows the possibility of these carbon-rich systems to mediate conductivity between metal centers.[110]
22 ! ! State of Knowledge ! !
PF6 X2 Ph2P PPh2 Ph2P PPh2 Ph Ph Ph Ph 1. CeIV, CH Cl H C C C Ru C C C 2 2 C C C Ru C C C Ph Ph 2. KB(C6F5)4 Ph Ph Ph2P PPh2 X = B(C6F5)4 Ph2P PPh2
Scheme 19. Reduction of trans-[Ph2C═C═C═(dppe)2Ru—C≡C―CHPh]PF6 with ammonium cerium(IV) nitrate [110] to trans-[Ph2C═C═C═(dppe)2Ru═C═C═CPh2][B(C6F5)4]2.
While carbon-rich ruthenium allenylidene complexes are no rarity, systems based on polyaromatic ligands are rare. One interesting spacer is the dipropargyl alcohol 10,10′- diethynyl-10H,10′H-[9,9′]bianthracenylidene-10,10′-diol that features the interesting nonplanar bianthracenylidene moiety. Bis(allenylidene) ruthenium(II) complexes based on this system can be obtained by reaction with two equivalents [RuCl(dppe)2]OTf. The addition of one equivalent affords the expected monoallenylidene derivative and the electrochemical and spectroelectrochemical properties were measured in detail (Scheme 20).[113] Both techniques highlighted the presence of electronic communication between the metal centers through the multiconjugated organic chains and allow allenylidene-centered reversible reductions, which are not interrupted on passing from mononuclear allenylidene complexes to dinuclear bisallenylidene complexes. This synthesis also allows the stepwise formation of heterobimetallic allenylidene complexes via stepwise reaction of the propargyl alcohol with selected ruthenium and rhenium precursors.
23 ! ! State of Knowledge ! !
OTf
Ph2P PPh2 OH Cl Ru C C C CH
Ph2P PPh2
+ 1 eq. [RuCl(dppe)2]OTf
CH OH
HO CH
+ 2 eq. [RuCl(dppe)2]OTf
(OTf)2
Ph2P PPh2 Ph2P PPh2 Cl Ru C C C C C C Ru Cl
Ph2P PPh2 Ph2P PPh2
Scheme 20. Synthesis of monoallenylidene and homobimetallic bisallenylidene complexes based on the bianthracenylidene linker.[113]
The dppe ligand system also allows the formation of further dinuclear allenylidene complexes based on homocoupling reactions of ruthenium diyne complexes and heterocoupling reactions between diyne complexes with allenylidene complexes.[102, 108, 114-116] Even larger trinuclear complexes are accessible from aromatic spacers bearing three propargyl alcohols as substitutes.[117]
24 ! ! State of Knowledge ! !
The group of κ3 coordinated cationic ruthenium allenylidene complexes consists mainly of N,N,N and S,S,S ligands, which are either facial or meridional coordinating. Cationic 18 VE ruthenium allenylidene complexes are known for systems based on 1,4,7-trithia- cyclononane,[93] trimethyl-1,4,7-triazacyclononane,[118] hydridotris(pyrazolyl)-borates,[119-121] 2,6-bis(oxazolyn-2"-yl)pyridines[122] and bis(pyrazol-1-yl)pyridines[123] but are mostly limited to the diphenyl allenylidene complexes.
The ligand system with the next higher coordination, the κ4-N,N,N,N-makrocycle 1,5,9,13- tetramethyl-1,5,9,13-tetraazacyclohexadecane (16-TMC), employed by C.-M. CHE et al. selectively forms the trans positioned allenylidene complexes bearing heteroatom donor units in the allenylidene residues.[124-125] The use of the dipyridyl allenylidene unit as a “molecular clip” allows the coordination of zinc or ruthenium ions to form either homo- or hetero- bimetallic allenylidene complexes (Scheme 21). DFT and TD-DFT calculations and experimental data showed delocalization along the [Ru═C═C═C(2-py)2Ru] moiety in the MLCT giving rise to NIR absorptions. This behavior highlights the potential application of allenylidene ligands as molecular bridges to allow electronic communication between remote functional groups.
Me Me N N N Cl Cl Ru C C C Zn N N N Cl + ZnCl2 Me Me Me Me N N N Cl Ru C C C N N N Me Me Me Me N N N + cis-[Ru(acac)2- Cl Ru C C C Ru(acac) (CH3CN)2] 2 N N N Me Me
Scheme 21. Synthesis of a heterobimetallic ruthenium zinc allenylidene complex and a homobimetallic ruthenium allenylidene complex based on 16-TMC.[125]
Important for this group of heteroatom based bimetallic complexes is the trans-arrangement of the chlorido and allenylidene ligand due to the competitive behavior of both towards the
25 ! ! State of Knowledge ! ! binding site. The irreversible formation of the allenylidene unit outcompetes the reversible κ1 coordination of the N-donor. Similar results were obtained with the trans-[RuCl(dppe)2] system.[126-128]
The group of cationic half-sandwich complexes does not only include the classical η5- cyclopentadienyl, η5-indenyl and η6-arene ruthenium complexes but also tethered type ligands in which an ancillary κ1-coordinating donor atom is introduced leading to η5: κ1(L)- or η6: κ1(L)-coordination. Most commonly η5 half-sandwich complexes bearing two phosphine ligands and one allenylidene moiety are reported following a similar procedure to the classical approach by J. SELEGUE (Scheme 13) leading to a general structure [Ru(η5-Ring)-
1 2 1 2 – – – – (═C═C═CR R )(L )(L )][X] with X = BF4 , BPh4 , PF6 and L1, L2 = PPh3, PMe3, PiPr3, dppe.[89-90, 129-138]
Recently, several remarkable examples by E. NAKAMURA et al. based on a ruthenium(II) fullerene-cyclopentadienyl complex bearing allenylidene ligands have been isolated (Figure 7).[139]
PF R2 6 Me C R1 PPh2 C Ph2P C Me Ru Me Me Me Me R1 = R2 = Ph R1 = H, R2 = Ph 1 2 R = H, R = 4-OMeC6H4 R1 = H, R2 = Fc 1 2 R = H, R = 4-NMe2C6H4
Figure 7. Ruthenium allenylidene complexes bearing a fullerene-cyclopentadienyl ligand.[139]
The focus of these complexes lies on the interaction of the physical and chemical properties of the allenylidene and fullerene moieties. On the one hand the bulkiness of the C60Me5 ligand leads to regio- and stereoselectivity for nucleophilic additions. On the other hand the intense absorptions of the aforementioned complexes in the visible and NIR region are of particular interest for their potential use in photophysical applications.[139-144]
26 ! ! State of Knowledge ! !
2.4.3 Neutral 18 Valence Electron Complexes
The third large group of ruthenium allenylidene complexes can be categorized as neutral 18 VE ruthenium allenylidene complexes. As mentioned above, several of these can be stabilized via Lewis acid and base interactions to form the more stable 18 VE adducts. Nevertheless, also genuine neutral 18 VE allenylidene complexes have been reported which are commonly based on anionic η5 or κ3 coordinating ligands. Although, mainly cationic allenylidene complexes based on Cp and Cp* are known, the allyl complexes [(η5-
3 5 3 C5H5)Ru(η -2-MeC3H4)(PPh3)] or [(η -C5Me5)Ru(η -2-MeC3H4)(PPh3)] allow also the formation of the corresponding neutral allenylidene complex following the method described
[145] by J. SELEGUE (Scheme 22). In comparison to [Ru(Cp)Cl(PPh3)2] the lack of the chlorido ligand in the reactant makes the chloride abstraction impossible. Addition of hydrochloric acid to the intermediary 16 VE complex leads to the coordination of a chlorido ligand and formation of the neutral 18 VE complex.
1. HC C C(Ph)2OH, HCl 2. Al O acidic Ru 2 3 Ru PPh3 PPh3 C Cl C Ph C
Ph
Scheme 22. Synthesis of a neutral 18 VE ruthenium allenylidene complex based on Cp.[145]
A further example for neutral allenylidene complexes is based on the κ3 facial coordinating hydridotris(pyrazol-1-yl)borate (Tp)[146] ligand developed by S. TROFIMENKO which has been widely used in ruthenium chemistry.[147-154] The follow-up chemistry often shows parallels to the related Cp complexes due to the close relation of half-sandwich complexes and the facially coordinated Tp analogs.[155-156] The corresponding ruthenium allenylidene complex is readily formed by reaction of [Ru(Tp)Cl(COD)] with different propargyl alcohols and phosphine ligands yielding allenylidene complexes of the general formula [Ru(Tp)Cl-
i i [93, 157] (═C═C═CR2)(L)] (L = PPh3, PCy3, P Pr3, PPh2 Pr) (Scheme 23). The reactivity of many allenylidene complexes, especially if they are cationic, concentrates on the addition of nucleophiles either to the Cα or Cγ carbon atom. Electron-rich allenylidene complexes, like the neutral Tp based systems, are capable of adding electrophiles at the Cβ carbon atom thereby forming vinylcarbyne complexes.[109, 158-160]
27 ! ! State of Knowledge ! !
H H B B 1 2 N N N HC C C(R R )OH N N N PR N N 3 N N N i 1 2 N PR3 = PPh2 Pr, R = R = Ph i 1 2 Ru PR3 = PPh2 Pr, R = R = Fc Ru Cl PR = PPh R1 = R2 = Ph R3P C 3 3, Cl C R1 i 1 2 PR3 = P Pr3, R = R = Ph C 2 R
Scheme 23. Synthesis of diphenyl and diferrocenyl (Fc) allenylidene complexes starting from [Ru(Tp)Cl(COD)].[157]
The Tp ligand and its complex chemistry is quite versatile, whereas a major drawback is the inherent lability of the borohydride bridge, which upon contact with water easily hydrolyses. Closely related to the Tp system is the bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) ligand that features two pyrazole units and an acetate moiety leading to the κ3 coordinating N,N,O motif. In the following chapter, a summary will be given on heteroscorpionate ligands and their use in bioinorganic, and especially organometallic ruthenium chemistry.
2.4.4 Reactions Involving Ruthenium Allenylidene Complexes as Precatalysts
In the chapter 2.2 the importance of metathesis reactions has already been briefly introduced. The great functional group tolerance of well-defined ruthenium carbene complexes
[LnRu]═CHR (i.e. Grubbs type catalysts) has led to a breakthrough in alkene metathesis chemistry within the last decades.[50, 161] Although the carbene-based catalyst are versatile and a powerful synthetic tool in organic and polymer chemistry the requirement of more accessible and active complexes leads to the development of new precatalysts. Especially easy to prepare and handle ruthenium allenylidene complexes are a valid alternative and several reviews concerning the properties of ruthenium allenylidene catalysts have been published.[77, 162-163]
The first example of RCM (ring closing metathesis) using an allenylidene complex was reported in 1998 by A. FÜRSTNER et al. and P. DIXNEUF et al. (Scheme 24).[164-166] They
6 employed [RuCl(═C═C═CR2)(η -p-cymene)(PR3)][X] as precatalyst for the conversion of
28 ! ! State of Knowledge ! !
N,N-diallyltosylamide into N-tosyldihydropyrrole. Three general trends could be observed: i) The activity of the catalyst increases with the electron richness off the phosphine
i ligand in the series PPh3 < P Pr3 < PCy3 the. ii) The employed counter anion has a drastic impact on the reactivity which increases
– – – – with the sequence BF4 < BPh4 ≈ PF6 < TfO . iii) While several substituted diarylallenylidene complexes have been tested the most potent was the simple diphenylallenylidene which showed values comparable to
[164-166] [RuCl2(═CHPh)(PCy3)2].
Ts Ts [RuCl(=C=C=CR2)- N 6 N (η -p-cymene)(PR3)][X] - C2H4
Scheme 24. Conversion of N,N-diallyltosylamide into N-tosyldihydropyrrole catalyzed by the precatalyst 6 [164-166] [RuCl(═C═C═CR2)(η -p-cymene)(PR3)][X].
A common rearrangement for diphenylallenylidene complexes is the formation of an indenylidene system that leads to a stronger repulsive interaction between the indenylidene group and the arene ligand resulting in a dissociation of the later. The generated vacant sites are required for substrate binding and the utility of isolated indenylidene complexes has been reported in detail by P. DIXNEUF et al.[158, 167] Due to the rigid structure of the fluorenyl unit no rearrangement into carbene complexes is possible thus, leading to a different mechanism that has not yet been fully understood.[163, 166]
2.5 Heteroscorpionate Chemistry
The aforementioned bdmpza ligand has been first reported by A. OTERO et al. in 1999 and can be synthesized starting from bis(3,5-dimethylpyrazol-1-yl)methane.[43] Deprotonation with n-butyllithium followed by reaction with carbon dioxide leads to the lithium compound
[43] [Li(H2O)(bdmpza)4]. A more versatile one-pot synthesis has been introduced by N. BURZLAFF et al. starting from either 3,5-dimethylpyrazole or unsubstituted pyrazole.[42] The reaction with dichloroacetic or dibromoacetic acid under basic conditions in the presence of a phase transfer catalyst allows after acidic workup the direct isolation of the protonated ligands Hbdmpza or Hbpza (bis(pyrazol-1-yl)acetic acid). In comparison to bpza the methyl 29 ! ! State of Knowledge ! ! substituents of the bdmpza ligand increase the solubility in common organic solvents and furthermore the steric hindrance. This leads in comparison to the air-stable complex
[Ru(bpza)Cl(PPh3)2] to an oxygen sensitive complex [Ru(bdmpza)Cl(PPh3)2] (Figure 8). The methyl substituents and the corresponding steric hindrance causes a smaller angle between the nitrogen donor atoms and the ruthenium center as observed in the crystal structure and thus leads to a labilization of the phosphine ligands.[168] This is remarkable as the closely related Tp complex [Ru(Tp)Cl(PPh3)2] and the Cp complex [Ru(Cp)Cl(PPh3)2] are air stable compounds which indicates that the steric hindrance of the bdmpza ligand strongly increases the tendency to release one phosphine ligand.[169-171]
H B Me Me N N N N N O N N N O N O O N N N N N Ru Me Ru Me Ru Ph3P Cl PPh3 Ph3P Cl PPh3 Ph P Cl PPh 3 3
Figure 8. Ruthenium based triphenylphosphine complexes bearing the Tp scorpionate ligand ([Ru(Tp)Cl(PPh3)2], left) and the heteroscorpionate ligands bdmpza ([Ru(bdmpza)Cl(PPh3)2], middle) and the ligand bpza [168-169] ([Ru(bpza)Cl(PPh3)2], right).
The class of pyrazole based N,N,O heteroscorpionates contains mainly acetic acid based systems, although more flexible ligands based on propionic acid have been introduced by E.
DÍEZ-BARRA et al. as sodium salt of 3,3-bis(pyrazol-1-yl)propionate (Na[bpzp]) and 3,3- bis(3,5-dimethylpyrazol-1-yl)propionate (Na[bdmpzp]).[172] The free acids and coordination properties have been explored by N. BURZLAFF et al.[173] Synthesis of these elongated N,N,O ligands involves a double Michael Addition of the pyrazole precursor to methyl propiolate. Depending on the aqueous workup this either affords the free acid or the corresponding sodium salt (Scheme 25). The coordination behavior of these two ligands has been explored with manganese carbonyl complexes as the CO vibrations can be monitored by IR spectroscopy and thus allows probing the electron donating and accepting properties of the ligands. Addition of [MnBr(CO)5] to the in-situ formed potassium salt (K[bdmpzp]) leads to the formation of the corresponding manganese(I) carbonyl complex fac-
[173] [Mn(bdmpzp)(CO)3]. Closely related are the complexes fac-[Re(bdmpza)O3] and fac-
[Tc(bpza)O3] which attracted attention for their possible application regarding radio-
30 ! ! State of Knowledge ! ! pharmaceutical purposes.[174-175] In comparison to the previously reported complexes fac-
[Mn(bdmpza)(CO)3] and fac-[Re(bdmpza)(CO)3] the elongated propionate based complex show only slight deviations in their chemical properties as for example the carbonyl ligand trans to the carboxylate anchor shows a longer distance to the manganese center and the coordination geometry around the manganese center is closer to perfect octahedral geometry due to the decreased strain.[173] For further work on the chemistry of N,N,N, N,N,S, N,N,O and N,N,Cp scorpionate ligands several reviews are available.[44, 176-180]
1. NaH COOH Me Me R 2. CO CH R R 1. KOtBu 2 3 N ON NH 3. H+/H O N N 2. [MnBr(CO )] 2 5 N O N N N N R = H, Me M = Mn, Re Me M Me R R R CO CO CO
Scheme 25. Synthesis of the propionic acid based ligands Hbpzp and Hbdmpzp via methyl propiolate; formation [172-173] of the manganese (I) and rhenium (I) carbonyl complexes [Mn(bdmpzp)(CO)3] and [Re(bdmpzp)(CO)3].
The aforementioned system [Ru(bdmpza)Cl(PPh3)2] has proven to show rich follow-up chemistry due to the labile triphenylphosphine and chlorido ligands. Moreover, the complex has been used as a model for the active site of 2-oxoglutarate dependent iron enzymes, which are often difficult to investigate due to their paramagnetic ferrous high-spin constitution. In comparison, the ruthenium based system with its low-spin state allows NMR characterization of the complexes. Conversion of [Ru(bdmpza)Cl(PPh3)2] with acetate or benzoate allows the
2 formation of the κ coordinated neutral ruthenium complexes [Ru(bdmpza)(O2CMe)(PPh3)] [181] and [Ru(bdmpza)(O2CPh)(PPh3)] (Scheme 26). In similar fashion the reaction of
[Ru(bdmpza)Cl(PPh3)2] with thallium 2-oxocarboxylates Tl[O2CC(O)R] (R = Ph,
2 1 2 CH2CH2CO2H) produces κ O ,O -2-oxocarboxylato complexes which can also be synthesized via the intermediary acetato or benzoato complexes due to the higher acidity of the oxocarboxylic acid. This is especially relevant for the catalytic cycle of the 2-oxoglutarate dependent enzymes, which has been postulated to show the exchange of a carboxylato ligand by a 2-oxocarboxylato ligand as a regenerative step.[182-183] The hemilabile behavior of the κ1O1,O1´ ligands allows the isolation of the water and acetonitrile adducts [Ru(bdmpza)-
(O2CMe)(H2O)(PPh3)] and [Ru(bdmpza)(O2CPh)(MeCN)(PPh3)] which are promising candidates for further reactions.[181]
31 ! ! State of Knowledge ! !
Me Me Me Me N N N N O O O O N N 1 N N + Tl[O2CR ] Me Ru Me Me Ru Me - TlCl, - PPh3 Ph P Cl PPh Ph P O O 3 3 O 3 R3 R1 O HO - TlCl 1 R2 O - HO2CR Tl O O Me Me N N O N O N R1 = Me, Ph R2 = Ph, CH CH CO H Me Ru Me 2 2 2 R3 = Me, Et Ph3P O O 4 R = Ph, CH2CH2CO2H, 4 Me, Et R O
Scheme 26. Formation of carboxylato and 2-oxocarboxylato ruthenium(II) complexes.[181]
The reaction of [Ru(bdmpza)Cl(PPh3)2] with pyridine, acetonitrile, carbon monoxide and sulfur dioxide has also been reported and has shown that the N,N,O ligand bdmpza leads to a preferred arrangement around the ruthenium center with the remaining triphenylphosphine ligand positioned trans to a pyrazole unit. The chlorido ligand is positioned trans to the acetate anchor in the aforementioned cases and leaves the newly introduced ligand in trans position to the remaining pyrazole unit. This behavior has been observed for the complexes
[61] [184] [Ru(bdmpza)Cl(CO)(PPh3)], [Ru(bdmpza)Cl(SO2)(PPh3)], [Ru(bdmpza)Cl(pyridine)- [185] [185] (PPh3)] and [Ru(bdmpza)Cl(MeCN)(PPh3)] (Scheme 27).
Me Me Me Me N N N N L = CO, O O N O N + L N O N SO2, py, - PPh3 Me Ru Me Me Ru Me MeCN Ph P Cl PPh Ph P Cl L 3 3 3
Scheme 27. Exchange reactions of the triphenylphosphine ligand in the [Ru(bdmpza)Cl(PPh3)2] system (py = pyridine, MeCN = acetonitrile).[61, 184-185]
The compound [Ru(bdmpza)Cl(PPh3)2] has also shown a versatile organometallic chemistry ranging from classical carbene and Fischer-type oxocarbene complexes to vinylidene and
32 ! ! State of Knowledge ! ! allenylidene complexes. The reaction of the bisphosphine ruthenium complex with a series of terminal alkynes led via 1,2-H shift of the intermediary η2 coordinated alkyne to the vinylidene complexes with the vinylidene ligand positioned trans to the pyrazole or carboxylate unit. The relation of the two formed isomers is attributed to the sterical hindrance of the respective alkyne complex during the η2 coordination preferring the arrangement trans to the pyrazole moiety for larger substituents. Up to now, the phenyl, tolyl, propyl and butyl substituted vinylidene complexes of the general formula [Ru(bdmpza)Cl(═C═CHR)(PPh3)] have been reported (Scheme 28).[61, 186]
Me Me Me Me Me Me N N N N N N O + H C C R O O N O N N O N N O N - PPh3 + Me Ru Me Me Ru Me Me Ru Me Ph P Cl PPh Ph P Cl C Ph P C Cl 3 3 3 C H 3 C R H R
Scheme 28. Synthesis of bdmpza based ruthenium vinylidene complexes with the cumulenylidene ligand positioned either trans to a pyrazole or the carboxylate unit (R = phenyl, tolyl, propyl, butyl).[186]
Due to the sensibility of the vinylidene complexes towards oxidation, a separation of the two occurring structural isomers cannot be achieved. Hence, the reactivity of the ruthenium precursor with propargyl alcohols was explored leading to the diphenyl and ditolyl substituted allenylidene complexes of the general formula [Ru(bdmpza)Cl(═C═C═CR2)(PPh3)] (R = phenyl, tolyl) which are stable towards air and humidity (Scheme 29). Separation via column chromatography allows the isolation of both structural isomers, which show different chemical and physical properties. Studies on the reactivity of these allenylidene complexes in metathesis reactions were disappointing as no catalytic activity could be observed, which is attributed to the stability of the 18 VE complex that does not undergo ligand dissociation to the reactive 16 VE species.
33 ! ! State of Knowledge ! !
Me Me Me Me Me Me N N N N N N O O O N O N N O N N O N + H C C CR2OH + Me Ru Me Me Ru Me Me Ru Me - PPh3 Ph P Cl PPh Ph P Cl C Ph P C Cl 3 3 3 C 3 C R C R C R R
Scheme 29. Synthesis of bdmpza based ruthenium allenylidene complexes with the cumulenylidene ligand positioned either trans to a pyrazole or the carboxylate unit (R = phenyl, tolyl).[186]
As mentioned in chapter 2.4.3 for the Tp based allenylidene complexes, the addition of nucleophiles usually occur either in α or γ position. For weak nucleophiles, like ammonia, the addition to the γ position on the complex [Cr(═C═C═C(OMe)NMe2)(CO)5] has been
[187] reported. The rearrangement of the Cγ ammonia adduct to the α-aminocarbene is known for the complex [Re(═C═C═CPh2)(CO)2(triphos)][OTf] (triphos = 1,1,1-tris(diphenyl- phosphinomethyl)ethane).[188] In the case of the reaction of [Ru(bdmpza)Cl-
(═C═C═C(tolyl)2)(PPh3)] with methylamine, the product can be obtained as aminocarbene complex indicating the higher reactivity of the α carbon atom which is in good agreement with DFT calculations (Scheme 30).[189]
Me Me Me Me N N N N O O N O N N O N
Me Ru Me + NH2Me Me Ru Me NHMe Ph P Cl C Ph P Cl C 3 C 3 Tol HC C C Tol Tol Tol
Scheme 30. Addition of methylamine to the complex [Ru(bdmpza)Cl(═C═C═C(tolyl)2)(PPh3)] yielding the corresponding aminocarbene complex.[189]
34
3 OBJECTIVE AND AIMS
35 ! ! Objective and aims ! !
During the last years a rich variety of heteroscorpionate complexes based on transition metals has been reported by the BURZLAFF group and other working groups and extensively reviewed by A. OTERO.[44, 173, 176, 180, 184-185, 189-190] In the field of manganese(I) carbonyl complexes bearing heteroscorpionate ligands I. HEGELMANN and L. PETERS of the BURZLAFF group synthesized
1-3 several complexes of the general formula [Mn(L )(CO)3] with the heteroscorpionate ligands bis(3,5-dimethylpyrazol-1-yl)acetate (L1 = bdmpza), bis(pyrazolyl)acetate (L2 = bpza) and 3,3-bis(3,5-dimethylpyrazol-1-yl)propionate (L3 = bdmpzp).[42, 173] Given the interest in medicinal applications of heteroscorpionate complexes, the carbon monoxide release properties of these and closely related manganese(I) carbonyl complexes should be investigated as first project within this thesis. Closely related is a topic previously investigated by S. TAMPIER and G. TÜRKOGLU concerning ruthenium carbonyl complexes with heteroscorpionate ligands. A single crystal X-ray structure determination of the dinuclear complex [Ru(bdmpza)(CO)(μ2-CO)]2 was obtained by serendipity and in consequence the rational synthesis of this compound should be explored within this work.
Especially the complex [Ru(bdmpza)Cl(PPh3)2] has shown a versatile organometallic chemistry including ligand exchange reactions leading to the 2-oxocarboxylato complex
[185] [Ru(bdmpza)(O2C(CO)Me)(PPh3)]. As these can be classified as bioinorganic model complexes for iron enzymes, the topic of aminophenol ligands and their non-innocent behavior should be explored starting from previous results of M. KECK.
Moreover, a major part of this thesis should be the synthesis and characterization of carbon- rich cumulenylidene complexes, i.e. ruthenium allenylidene and vinylidene complexes. The starting point was previous work by H. KOPF on the synthesis of neutral bdmpza based
[61, 186, 189] ruthenium complexes with the general formula [Ru(bdmpza)Cl(L)(PPh3)]. Thus within this work several new carbon-rich propargyl alcohols should be synthesized and the reaction to the corresponding ruthenium allenylidene complex should be performed. The properties of the resulting allenylidene complexes should be characterized with a focus on cyclic voltammetry and absorption spectroscopy. As a side project the formation of water- soluble carbon-rich allenylidene complexes should be explored for possible applications in non-covalent functionalization of carbon allotropes.
36
4 RESULTS AND DISCUSSION
37 ! ! Results and Discussion ! !
4.1 Manganese Based Photo-CORMs
Recently, P. KURZ and coworker compared the CO-release properties of [Mn(bdmpza)(CO)3] (1) (bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate), that was published by the BURZLAFF group some years ago, to that of a related tris(pyrazol-1-yl)methane (tpm) complex.[42, 191] Given the interest in medicinal applications of heteroscorpionate complexes, it was decided to explore the carbon monoxide release properties of such heteroscorpionate manganese(I) carbonyl complexes further. During the last decade, the BURZLAFF group has reported on the synthesis of various manganese(I) complexes based on heteroscorpionate ligands. Up to date, the complexes [Mn(bdmpza)(CO)3] (1), [Mn(bpza)(CO)3] (2) (bpza = bis(pyrazol-1- yl)acetate), and [Mn(bdmpzp)(CO)3] (3) (bdmpzp = 3,3-bis(3,5-dimethylpyrazol-1-yl)- propionate) have been described.[42, 173] Due to the rising interest in CORMs, especially with
[192] Alfama´s lead compound fac-[Mo(CO)3(histidinate)]Na (ALF-186), which also features a κ3 coordinated N,N,O motif, we decided to synthesize the missing link, a manganese(I) complex bearing a 3,3-bis(pyrazol-1-yl)propionic acid (Hbpzp) and to study the complexes towards their CO-release properties (Scheme 31).
R R R R N N N O N O N O N or N O N potassium carboxylate [MnBr(CO) ] + 5 of the scorpionate R Mn R R Mn R OC CO OC CO CO CO R = Me (1), H (2) R = Me (3), H (4)
Scheme 31. Synthesis of heteroscorpionate complexes [Mn(bdmpza)(CO)3] (1), [Mn(bpza)(CO)3] (2), [42, 173] [Mn(bdmpzp)(CO)3] (3) and [Mn(bpzp)(CO)3] (4).
The ligands and complexes were synthesized according to reported procedures.[42, 173] Deprotonation of the free acids (e.g. Hbpzp) with potassium tert-butylate lead to the potassium carboxylates (e.g. K[bpzp]). Reaction of [MnBr(CO)5] with these carboxylates resulted in the formation of tricarbonyl complexes [Mn(heteroscorpionate)(CO)3] (1-4). The new complex [Mn(bpzp)(CO)3] (4) could be filtered off after spontaneous precipitation from the reaction mixture. Complex 4 is stable towards oxygen as a solid but decomposes in solution within some hours, as described previously for complexes 1-3.[42, 173] In comparison to
38 ! ! Results and Discussion ! ! the dimethylpyrazole based complex [Mn(bdmpzp)(CO)3] (3), its solubility in most solvents is lower. The two pyrazolyl groups of 4 give rise to only one set of signals in the 1H NMR spectrum in accordance with the expected Cs structure. Due to poor solubility, no carbonyl signals could be detected in the 13C NMR spectrum. Nevertheless, the IR spectrum shows three carbonyl signals (A’, A’’ and A’) at 2026, 1932 and 1915 cm–1, as expected for a facial coordinated tricarbonyl complex with Cs symmetry.
Furthermore, the complex [MnBr(CO)3(Hpz)2] (5) was included in this study representing a simplified analogue of complexes 2 and 4 and that - from a synthetic point of view - is a lot simpler to prepare (Scheme 32). Moreover, it was tried to synthesize the analogous imidazole based manganese(I) complex but the reaction of one equivalent [MnBr(CO)5] with two equivalents of imidazole in CH2Cl2 over 5 h only led to the formation of the cationic manganese complex [Mn(CO)3(HIm)3]Br (6) (Scheme 32).
Br NH NH N HN N 2 HPz 3 HIm OC N [MnBr(CO)5] N N NH Mn N Mn OC BrH OC CO CO CO 5 6
[193] Scheme 32. Synthesis of manganese based complexes [MnBr(CO)3(HPz)2] (5) and [Mn(CO)3(HIm)3]Br (6).
1 13 The high symmetry (C3v) of complex 6 is emphasized by the H NMR and C NMR spectra. Both spectra show only one set of signals for all relevant positions including the amine protons at 12.97 ppm in the 1H NMR spectrum and the carbonyl ligands at 220.3 ppm in the 13C NMR spectrum. ESI-MS experiments showed that the cation can be detected at m/z = 343.05 which is the characteristic [M]+ signal for the complex after loss of the counter ion.
The 13C NMR and IR data of the carbonyl ligands in complexes 1-6 is listed in Table 2. The characteristic facial coordinating motif of the heteroscorpionate N,N,O ligands leads to the
[42-43, 173] formation of complexes with Cs symmetry as has been shown previously. This reduced symmetry compared to the C3v symmetrical tpm M(CO)3 based complexes gives rise to three
IR absorption bands (A’, A’’ and A’) for the CO vibrations. Due to its higher C3v symmetry, complex 6 exhibits only two characteristic CO vibrations in the IR spectrum.
39 ! ! Results and Discussion ! !
Ligand Complex δ (CO) [ppm] ṽ (CO)(KBr) [cm–1]
bdmpza 1 219.8 2038, 1954, 1931
bpza 2 219.3 2039, 1956, 1917
bdmpzp 3 222.0 2030, 1925, 1899
bpzp 4 / 2028, 1947, 1929
2 × Hpz, 1 × Br– 5 222.8 2035, 1940, 1918
3 × HIm 6 220.3 2024, 1907
Table 2. Overview of relevant 13C NMR and IR spectroscopic data of compounds 1-6.
CO release properties
In order to study the properties of the new compounds as photoactivatable CO releasing molecules (Photo-CORMs), the manganese complexes 1-6 were investigated using the UV/Vis based myoglobin assay. Complex 1 has been reported previously to show Photo- CORM activity,[191] but due to a slightly different assay, it was decided to reassess the values to facilitate comparison with compounds 2-6. Prior to measuring the release upon UV excitation, the stability of each compound was tested in the dark. Complexes 1-3 were stable and did not show any decomposition during 6 h. Nevertheless, complexes 4-6 showed CO release upon dissolution in aqueous media in the dark. Similar behavior has previously been reported for the precursor [Mn(CO)5]Cl, which forms the aqua complex + [194] [Mn(CO)3(H2O)3] . Complex 4 exhibited slow release within a timeframe of 24 h yielding 1.42 ± 0.04 eq. of carbon monoxide with an average half life of 217 min (Chapter 8.3, Figure 64). For bis(imidazol-2-yl)propionate (bip) based complexes, a betain-like structure has been reported with a κ2 coordination of the bis(imidazo-2-yl)methane moiety and a dissociated propionate anchor.[195] A similar dissociation of the carboxylate donor might explain the low stability of 4 in solution, but up to now it was not possible to isolate such an intermediate. The pyrazole-based compound 5 shows faster decomposition in the dark, releasing 1.14 ± 0.09 eq.
CO with t1/2 = 124 min (Chapter 8.3, Figure 65). In contrast, the cationic imidazole complex 6 shows the fastest CO release in the dark with a t1/2 = 73 min and the release of 2 eq. CO
40 ! ! Results and Discussion ! !
(1.94 ± 0.39) (Chapter 8.3, Figure 66). Nevertheless, it was decided to take a look at the effect of photoactivation of 5 and 6 with UV light to see if complete CO release can be achieved.
3.0
2.5
2.0
eq. (CO) 1.5
1.0
0.5
0.0 0 5 10 15 20 25 30 t [min]
Figure 9. Fitted average CO release of 6 (squares) and 5 (dots) measured via myoglobin assay.
For complex 5, a strong acceleration of the CO release was achieved via UV excitation
(365 nm), lowering the release time to t1/2 = (6.40 ± 0.14) min and yielding an increased amount of equivalents CO (2.17 ± 0.09 eq.) (Figure 9). In comparison, 6 shows an even higher activity under these conditions, releasing about 2.5 equivalents of carbon monoxide in
20 min (t1/2 = 5.56 min, 2.60 ± 0.35 eq.). Due to the different coordination sphere of the manganese(I) center with two pyrazole or three imidazole ligands, a direct comparison is difficult. However, removal of the ligand backbone from either tris(imidazol-2-yl)phosphanes or bis(pyrazol-1-yl)acetate leads to manganese tricarbonyl complexes that are not stable under the conditions of the myoglobin assay.[196]
In the next step, the Photo-CORM properties of the compounds, which showed no CO release in the dark were evaluated. For 1, a t1/2 = 6.73 min with a release of 2.38 ± 0.11 eq. of carbon monoxide was observed upon photoactivation at 365 nm, which is in good accordance with the literature value of 2.5 eq. (Figure 10).[191] Compound 2 lacks the methyl substituents as in complex 1 and shows slower CO release. With 2.15 ± 0.11 eq. and t1/2 = 11.35 min, the complex seems to be more stable than the methyl substituted one, which is in agreement with previous observations regarding these ligands.[168] In a similar context, the ruthenium based system [Ru(bpza)Cl(PPh3)2] is quite stable towards oxygen, whereas the bulkier methyl- 41 ! ! Results and Discussion ! ! substituted [Ru(bdmpza)Cl(PPh3)2] is highly oxidation sensitive and decomposes within hours in the presence of oxygen.[168]
2.5
2.0
1.5
eq. (CO) 1.0
0.5
0.0 0 5 10 15 20 25 30 t [min]
Figure 10. Fitted average CO release of 1 (squares), 2 (dots) and 3 (triangles) measured via myoglobin assay.
Extending the acetate anchor to a propionate leads to complex 3, which has the fastest CO release kinetics of the compounds presented within this work. Full release of 2 eq. CO has been observed after less than 15 min with t1/2 = 3.77 min (2.06 ± 0.09 eq.). This might be due to the propionate based ligand that allows more dynamic behavior in the resulting complexes. The less rigid coordination seems to facilitate the dissociation of carbonyl ligands compared to the acetate based ones. The difference in CO-release rate between 3 and 4 seems to be strongly influenced by the methyl substituents. Obviously, in this case, the methyl groups stabilize the complex, hinder the mobility of the carboxylate anchor and prevent solvent- controlled dissociation of CO molecules for 3. The proton-substituted complex 4 is however, not stable in solution and solvent-controlled dissociation of the carbonyl ligands occurs in the dark.
In Table 3, the properties of several literature known Photo-CORMs are collected. Comparison with the heteroscorpionate complexes shows that on average, only two of the three CO ligands per complex are released. The half life of the complexes presented in this work is shorter than most of the compounds described so far in the literature, but varies significantly with the ligand system.
42 ! ! Results and Discussion ! !
Complex t1/2 [min] eq. (CO) Reference
[a] 1 [Mn(bdmpza)(CO)3] 7 2.38
[a] 2 [Mn(bpza)(CO)3] 11 2.15
[a] 3 [Mn(bdmpzp)(CO)3] 4 2.06
[36] [Mn(tpm)(CO)3]PF6 20 1.96
[197] fac-[Mn(his)(CO)3] 93 1.26
[32] [Mn2(CO)10] (CORM-1) not determined 0.68
Table 3. Photoinduced CO release upon UV excitation for manganese(I) carbonyl complexes, with half-lifes and number of CO molecules released per complex determined with the myoglobin assay; [a] reported in this work.
43 ! ! Results and Discussion ! !
4.2 Ruthenium Carbonyl Complexes Bearing Bis(pyrazol-1-yl)carboxylato Ligands
Parts of this chapter have been published:
Türkoglu, G.; Tampier, S.; Strinitz, F.; Heinemann, F. W.; Hübner, E.; Burzlaff, N., Organometallics 2012, 31, 2166-2174.
Bis(pyrazol-1-yl)acetic acids have proven to be a versatile N,N,O heteroscorpionate ligand closely related to the well known hydridotris(pyrazol-1-yl)borate (Tp) ligand as mentioned in the introduction. Several ruthenium(II) complexes like [Ru(bdmpza)Cl(PPh3)2] and recently
[Ru(2,2-bdmpzp)Cl(PPh3)2] (2,2-bdmpzp = 2,2-bis(3,5-dimethylpyrazol-1-yl)propionic acid) have been reported by N. BURZLAFF et al. and other groups.[61, 168, 181, 184-185, 189-190, 198-201] Some of these ruthenium(II) complexes are good structural models for iron oxygenases that exhibit a facial 2-His-1-carboxylate triad as a ferrous iron binding motif.[181, 190] The uncatalyzed reaction of organic compounds with atmospheric dioxygen is thermodynamically feasible but is a spin-forbidden process. In nature, iron oxygenases make use of their high-spin ferrous centers to overcome this spin mismatch.[202-206] Thus, an analogous enzyme activation of dioxygen with ruthenium(II) complexes is not favorable due to their low-spin character. However, the necessity of a high-spin center becomes irrelevant in so-called peroxide shunt type reactions. Oxidizing agents such as peroxides and iodosylbenzene are used to directly
IV VI generate high-valent and reactive Ru ═O or Ru (═O)2 species which are able to catalytically epoxidize alkenes, oxidize sulfides, or hydroxylate alkanes.[207-214] C.-M. CHE and co-workers, for instance, reported on cationic ruthenium(IV) complexes such as [Ru(Me3tacn)(3,3′-Me2- bpy)(O)]2+ and [Ru(terpy)(tmeda)(O)]2+ that can be used to epoxidize alkenes stoichiometrically (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane, 3,3′-Me2bpy = 3,3′- dimethyl-2,2′-bipyridine, terpy = 2,2′:6′,2′′-terpyridine, tmeda = N,N,N′,N′-tetramethyl-
[215-218] ethylenediamine). Furthermore, the complex [Ru(Me3tacn)(OH2)(O2CCF3)](O2CCF3)2 was shown to be an effective catalyst for homogeneous oxidation of alkenes by tert-butyl hydroperoxide (TBHP) as an oxidant.[219] Thus, in previous experiments some of the ruthenium bdmpza complexes mentioned above, such as [Ru(bdmpza)Cl(PPh3)2] and
[Ru(bdmpza)(OAc)(PPh3)], were tested for their catalytic activity in similar alkene 44 ! ! Results and Discussion ! ! epoxidations.[220] Unfortunately, rather poor catalytic activity with only 2−3 turnovers was observed, due to large quantities of O═PPh3 byproduct, which inhibit the catalytic epoxidation. Thus, it was decided to focus on phosphine-free complexes for further studies. S.
TAMPIER and G. TÜRKOGLU synthesized [Ru(bdmpza)Cl(CO)2] (9) and [Ru(2,2-bdmpzp)Cl- [221] (CO)2] (10) starting from [RuCl2(CO)2]n that has been reported by J. VOS et al. as quite useful and easily accessible precursor for phosphine free ruthenium chemistry.[222-223] Addition of the respective potassium salt of the heteroscorpionate ligand leads to formation of the mononuclear ruthenium complex (Scheme 33).
CO H R Me R 2 Me 1. KOtBu Me Me N N 2. [RuCl2(CO)2]n N N O N N N O N Me Me Me Ru Me OC CO Cl R = H (7) R = H (9) R = Me (8) R = Me (10)
Scheme 33. Synthesis of dicarbonyl complexes [Ru(bdmpza)Cl(CO)2] (9) and [Ru(2,2-bdmpzp)Cl(CO)2] (10).
In addition the formation of the dinuclear byproduct [Ru(bdmpza)(CO)(μ2-CO)]2 was observed in the FAB+ mass spectrum as indicated by the molecular ion peak (m/z 810, 4%). Thus, it was not surprising that, in attempts to crystallize complex 9, crystals of this byproduct [Ru(bdmpza)(CO)(μ2-CO)]2 (12) suitable for an single-crystal X-ray structure determination were isolated by S. TAMPIER.[222] The structure determination revealed its
[222] molecular structure as a dinuclear μ2-CO complex as reported in his dissertation.
There are several procedures described in the literature for the synthesis of the analogous
5 cyclopentadienyl compound [Ru(η -C5H5)(CO)(μ2-CO)]2. Thus, attempts were undertaken to 5 rationally synthesize this compound. E. O. FISCHER et al. synthesized [Ru(η -C5H5)(CO)(μ2- [224] CO)]2 via reaction of the ruthenium(II) precursor [Ru(CO)2I2] with an excess of sodium [225] cyclopentadienide, Na[C5H5]. Attempts to adopt this procedure by using potassium bis(3,5- dimethylpyrazol-1-yl)acetate instead of Na[C5H5] failed because of the insolubility of K[bdmpza] in the aliphatic solvent. In further attempts an oxidative addition of bis(3,5- dimethylpyrazol-1-yl)acetic acid to [Ru3(CO)12] was tested. This should result in the hydrido complex [Ru(bdmpza)H(CO)2] (11), which might then be oxidized by oxygen and dimerize to 5 [226-227] [Ru(bdmpza)(CO)(μ2-CO)]2 (12) as reported for [Ru(η -C5H5)(CO)(μ2-CO)]2. Indeed,
45 ! ! Results and Discussion ! ! the 1H NMR spectrum of the resulting product indicated formation of two hydrido complexes by two singlet signals at −13.32 and −10.10 ppm (in CDCl3) (Scheme 34). These signals have been assigned to two structural isomers, the symmetrical hydrido complex [Ru(bdmpza)-
H(CO)2] (11A) and the unsymmetrical hydrido complex [Ru(bdmpza)H(CO)2] (11B). In the
Cs symmetric isomer 11A the hydrido ligand resides trans to the carboxylate and only one set of signals is observed for the two 3,5-dimethylpyrazole donors in the 1H NMR spectrum, whereas the C1 symmetric, chiral, but racemic complex [Ru(bdmpza)H(CO)2] (11B) shows two sets of signals in the 1H NMR spectrum, instead.
Me Me Me Me Hbdmpza N N N N [Ru3(CO)12] O + O toluene, Δ N O N N O N Me Ru Me Me Ru Me OC CO H OC H CO 11A 11B HOAc Me
N N Me O Me N O O CO C Me Hbdmpza N [Ru(OAc)(CO)2]n Ru Ru THF, Δ C Me OC O N - HOAc O N Me NO Me N
12 Me
Scheme 34. Synthesis of complexes [Ru(bdmpza)H(CO)2] (11A,B) and [Ru(bdmpza)(CO)(μ2-CO)]2 (12).
The solubility of the hydrido complex [Ru(bdmpza)H(CO)2] (11A,B) is rather poor in most solvents apart from CHCl3 and CH2Cl2. Unfortunately, the complex decomposes quickly in
CDCl3 by formation of the chlorido complex, a reactivity that was reported for other hydrido 5 [225] complexes such as [Ru(η -C5H5)H(CO)(PPh3)]. In CD2Cl2 the stability of the complex is slightly better. Thus, only 1H NMR data could be obtained so far. Nevertheless, ESI-MS data and elemental analysis prove the formation of 11A,B. Surprisingly, so far it was not possible to isolate 12 from solutions of the hydrido complex [Ru(bdmpza)H(CO)2] (11A,B), that had been exposed to air. Obviously, the hydrido complex 11A,B seems to be quite unreactive regarding oxygen. Even heating under reflux in nonpolar solvents such as n-heptane and 46 ! ! Results and Discussion ! ! applying aerobic conditions did not yield complex 12 but mostly unreacted 11A,B. Thus, another attempt was undertaken by reacting the acetate polymer catena-[Ru(OAc)(CO)2]n with Hbdmpza. The polymer catena-[Ru(OAc)(CO)2] is readily available but is also easily [228] accessible by reacting [Ru3(CO)12] with acetic acid. It has been successfully applied in the syntheses of various dinuclear ruthenium(I) complexes before.[229-230] Reaction in THF at reflux for 24 h replaced the acetate of catena-[Ru(OAc)(CO)2]n by bis(3,5-dimethylpyrazol-1- yl)acetic acid and resulted in the target complex [Ru(bdmpza)(CO)(μ2-CO)]2 (12) in a yield of 30%. The constitution of the molecule is confirmed by elemental analysis as well as by ESI- MS data in acetonitrile, which show a 100% peak at m/z 405.02 (100) assigned to a
+ [Ru(bdmpza)(CO)2] fragment and a small (4%) molecular ion peak at m/z 810.05. Due to the low solubility of 12 in all common deuterated solvents, only 1H NMR data could be obtained so far. As expected for the C2h-symmetric molecule depicted in Scheme 34, only one set of signals is observed, with the methyl singlet signals at 2.35 (Me3) and 2.62 ppm (Me5). The pyrazole CH proton is found at 6.04 ppm and the methine proton at 6.31 ppm. In theory at least three isomeric forms of complex 12 might be possible: (I) terminal trans-CO/μ2-CO bridged, (II) terminal cis-CO/μ2-CO bridged, (III) nonbridged. Apparently, according to the NMR data only one of these possible isomeric forms seems to be present in solution. This is
5 in contrast to [Ru(η -C5H5)(CO)(μ2-CO)]2, where an equilibrium of various isomeric forms was reported.[231-234] The bdmpza ligand exhibits its typical IR vibrations at 1673 cm–1 (as-
– –1 3 CO2 ) and 1559 cm (C═N) as expected for κ coordination. The IR spectrum in solution
(CHCl3) is almost identical with that obtained in a KBr matrix. IR vibrations (CHCl3) at –1 –1 1978 cm (terminal CO) and 1761 cm (μ2-CO) agree well with those reported for μ2-CO 5 –1 isomers of [Ru(η -C5H5)(CO)(μ2-CO)]2 (ν(CO) (CHCl3) 2009 cm (terminal CO) and –1 –1 –1 [233] 1768 cm (μ2-CO); ν(CO) (MeCN) 1995 cm (terminal CO) and 1775 cm (μ2-CO)).
Thus, owing to the observed very strong μ2-CO vibration one μ2-CO isomer seems to dominate in the solid state as well as in solution. Nevertheless, a very weak shoulder around 2010 cm–1 and a weak signal at 1950 cm–1 might indicate traces of a nonbridged species.
Similar results could be obtained with the sterically less demanding bpza ligand, as the
[235] bridged complex could be synthesized. However, the complex [Ru(bpza)Cl(CO)2] (13) was still missing. 13 can be easily synthesized in analogy to [Ru(bdmpza)Cl(CO)2] (9) by adding the potassium salt of the bpza ligand and heating under reflux (Scheme 35).
47 ! ! Results and Discussion ! !
CO H 2 1. KOtBu N N O O N N 2. [RuCl2(CO)2]n N N N N THF Ru OC CO Cl 13
Scheme 35. Synthesis of dicarbonyl complex [Ru(bpza)Cl(CO)2] (13).
The complex [Ru(bdmpza)Cl(CO)2] (9) shows high solubility in CH2Cl2 and CHCl3, in comparison [Ru(bpza)Cl(CO)2] (13) remains completely insoluble and can only be characterized as DMSO or methanol solution. 13 shows in the 1H NMR spectrum six protons for the two pyrazolyl units indicating that the chlorido ligand is positioned trans to a pyrazole moiety and thus an asymmetric bpza ligand without a mirror plane is isolated. The 13C NMR spectrum confirms the presence of two asymmetric carbonyl ligands at 194.8 and 193.9 ppm that are positioned trans to the second pyrazole moiety and the acetate anchor. The complex shows two intense absorptions at 2081 and 2014 cm–1 in the IR absorption spectrum in a similar region to 9 (2074 cm–1, 2005 cm–1).[236] Two additional very weak absorptions at 1768 and 1760 cm–1 indicate that traces of the dimeric complex could be present however, attempts of removal via recrystallization from DMSO did not lead to disappearance. The complex could further be characterized via ESI-MS experiments showing the presence of the sodium
+ adduct of 13 as 100% peak at m/z 406.91 (100) assigned to a [Ru(bpza)Cl(CO)2 + Na] cluster. Crystals suitable for a single crystal X-ray structure determination were obtained by dissolving 13 in boiling methanol and afterwards vapor diffusion of Et2O into the methanolic solution at room temperature. [Ru(bpza)Cl(CO)2] (13) crystallizes as two independent molecules in the space group C2/c and shows co-crystallization of methanol and Et2O. The complex shows the arrangement deduced from the NMR data and shows the chlorido ligand trans to a pyrazole moiety leading to two non-equivalent carbonyl ligands trans to the remaining pyrazole unit and trans to the carboxylate anchor (Figure 11).
48 ! ! Results and Discussion ! !
O2
N22 N12
O1 N21 N11 Ru C31 C41 Cl O3 O4
Figure 11. Preliminary molecular structure of [Ru(bpza)Cl(CO)2] (13). Hydrogen atoms and solvent molecules have been omitted for clarity.
To elucidate the spectroscopic properties and the binding situation in [Ru(bdmpza)(CO)(μ2-
CO)]2 (12) further, DFT calculations were performed by E. HÜBNER starting from the X-ray structure determination data. The resulting geometry of the DFT calculations was almost identical with the geometry of the X-ray structure determination. The spin density of the two electrons forming the Ru−Ru bond is mainly located at the metal centers and the bridging carbonyl ligands (Figure 12). Surprisingly, the spin density plot does not resemble the contour plots of two dz2 orbitals but the contour plots of dxy, dxz or dyz orbitals. This implies that the Ru−Ru bond is better described as a π bond than as a σ bond. In order to verify the IR signals of 12, DFT calculations were performed. It is well-known for the chosen B3LYP/6-31G* DFT functional and basis set, that calculated vibrational frequencies are typically overestimated in comparison to experimental data. These errors arise from the neglect of anharmonicity effects, incomplete incorporation of electron correlation, and the use of finite basis sets in the theoretical treatment.[237] In order to achieve a correlation with observed spectra, a scaling factor of approximately 0.96 has to be applied.[237] Depending on the examined vibration, this factor differs slightly even in the same molecule and is usually greater for lower energies.[238]
49 ! ! Results and Discussion Organometallics ! ! Article polymer catena-[Ru(OAc)(CO)2]n with Hbdmpza. The poly- mer catena-[Ru(OAc)(CO)2]n is readily available but is also 54 easily accessible by reacting [Ru3(CO)12] with acetic acid. It has been successfully applied in the syntheses of various dinuclear ruthenium(I) complexes before.42,49 Reaction in THF at reflux for 24 h replaced the acetate of catena-[Ru(OAc)- (CO)2]n by bis(3,5-dimethylpyrazol-1-yl)acetic acid and resulted in the target complex [Ru(bdmpza)(CO)(μ2-CO)]2 (6) in a yield of 30%. The constitution of the molecule is confirmed by elemental analysis as well as by ESI MS data in acetonitrile, which show a 100% peak at m/z 405.02 (100) + assigned to a [Ru(bdmpza)(CO)2] fragment and a small (4%) molecular ion peak at m/z 810.05. Due to the low solubility of 6 in all common deuterated solvents, only 1H NMR data could be obtained so far. As expected for the C2h-symmetric molecule depicted in Figure 3, only one set of signals is observed, with 3 Figure 4. Spin density plot regarding the electrons forming the Ru− the methyl singlet signals observed at 2.35 (Me ) and 2.62 Figure 12. Spin density plot regarding the electrons forming the Ru−Ru bond. (Me5) ppm. The pyrazole CH proton is found at 6.04 ppm and Ru bond. the methine proton at 6.31 ppm. In theory at least threeWe were especially interested in the two carbonyl vibra56 tions, which were predicted (unscaled) isomeric forms of complex 6 might be possible: (I) terminal sets in the theoretical treatment. In order to achieve a −1 −1 μ μ at 2078 cm correlation (terminal CO) with and observedat 1851 cm spectra, (μ2-CO). aThis scaling leads to factor expected of vibrations at trans-CO/ 2-CO bridged, (II) terminal cis-CO/ 2-CO bridged, 56 (III) nonbridged. Apparently, according to the NMR data1995 only and 1777approximately cm−1. Both values 0.96 agree has towell be with applied. the experimentalDepending data. onIn further the agreement examined vibration, this factor differs slightly even in the same one of these possible isomeric forms seems to be presentwith in the experimental data, the trans geometry of the bridged isomer57 of 12 was found to be solution. This is in contrast to the case for [Ru(η5- molecule and is usually greater for lower energies. We were the lowest especially in energy. interested The energy in difference the two carbonyl between vibrations, the bridged which and nonbridged were species C5H5)(CO)(μ2-CO)]2,whereanequilibriumofvarious 50,55 −1 isomeric forms was reported. The bdmpza ligand exhibits(Figure 13) predictedwas found (unscaled) to be rather at small, 2078 with cm ΔE(terminal = 22 kJ/mol CO) in andcomparison at 1851 to an energy −1 − −1 cm−1 (μ -CO). This leads to expected vibrations at 1995 and its typical IR vibrations at 1673 cm (as-CO2 ) and 1559 cm 2 3 difference of ΔE = 45−1 kJ/mol between the cis and trans geometries. The low energy (CN) as expected for κ coordination. The IR spectrum in 1777 cm . Both values agree well with the experimental data. difference towardIn further the unbridged agreement isomer with implies the experimental a rather high data, possibility the trans of finding the solution (CHCl3 solvent) is almost identical with that obtained −1 geometry of the bridged isomer of 6 was found to be the lowest in a KBr matrix. IR vibrations (CHCl3) at 1978 cm (terminalnonbridged isomer in solution, which may agree with the data of the IR spectra discussed −1 in energy. The energy difference between the bridged and CO) and 1761 cm (μ2-CO) agree well with those reported 5 above. The nonbridgedstrong asymmetric (Figure IR vibrations 5) species of wasthe nonbridged found to beCO ratherwere predicted small, (unscaled) for μ2-CO isomers of [Ru(η -C5H5)(CO)(μ2-CO)]2 (ν(CO) −1 −1 −1 −1 (CHCl3 solvent) 2009 cm (terminal CO) and 1768 cmat 2075 and 2047 cm , which should result in vibrations around 1992 and 1965 cm . −1 (μ2-CO); ν(CO) (MeCN solvent) 1995 cm (terminal CO) −1 55b and 1775 cm (μ2-CO)). Thus, owing to the observed very strong μ2-CO vibration one μ2-CO isomer seems to dominate in the solid state as well as in solution. Nevertheless, a very weak shoulder around 2010 cm−1 and a weak signal at 1950 cm−1 might indicate traces of a nonbridged species. Due to the steric hindrance of the bdmpza ligands and in accord with DFT calculations (see below), the μ2-CO isomer cis-[Ru(bdmpza)- (CO)(μ2-CO)]2 (isomer II) with cis geometry of the terminal CO ligands seems to be thermodynamically disfavored. Thus, in accordance with the solid-state structure (Figure 3) trans- [Ru(bdmpza)(CO)(μ2-CO)]2 (6) (isomer I) is the main isomeric form. To elucidate the spectroscopic properties and μ the binding situation in [Ru(bdmpza)(CO)( 2-CO)]2 (6) 50 further, DFT calculations were performed for 6 starting from the X-ray structure determination data. The resulting geometry of the DFT calculations was almost identical with the geometry of the X-ray structure determination. The spin density of the Figure 5. Calculated geometry of a nonbridged isomer of 6. two electrons forming the Ru−Ru bond is mainly located at the metal centers and the bridging carbonyl ligands (Figure 4). with ΔE = 22 kJ/mol in comparison to an energy difference of Surprisingly, the spin density plot does not resemble the ΔE = 45 kJ/mol between the cis and trans geometries. The low 2 contour plots of two dz orbitals but the contour plots of dxy, energy difference toward the unbridged isomer implies a rather dxz, or dyz orbitals. This implies that the Ru−Ru bond is better high possibility of finding the nonbridged isomer in solution, described as a π bond than as a σ bond. In order to verify the IR which may agree with the data of the IR spectra discussed signals of 6, DFT calculations on 6 were performed. It is well- above. The strong asymmetric IR vibrations of the nonbridged known for the chosen B3LYP/6-31G* DFT functional and CO were predicted (unscaled) at 2075 and 2047 cm−1, which basis set that calculated vibrational frequencies are typically should result in vibrations around 1992 and 1965 cm−1. overestimated in comparison to experimental data. These errors Experiments regarding the oxidation of cyclohexene arise from the neglect of anharmonicity effects, incomplete mediated by complexes 3 and 4 were carried out in incorporation of electron correlation, and the use of finite basis unstabilized, HPLC grade CH2Cl2 under a dinitrogen
2170 dx.doi.org/10.1021/om2009155 | Organometallics 2012, 31, 2166−2174 Organometallics Article polymer catena-[Ru(OAc)(CO)2]n with Hbdmpza. The poly- mer catena-[Ru(OAc)(CO)2]n is readily available but is also 54 easily accessible by reacting [Ru3(CO)12] with acetic acid. It has been successfully applied in the syntheses of various dinuclear ruthenium(I) complexes before.42,49 Reaction in THF at reflux for 24 h replaced the acetate of catena-[Ru(OAc)- (CO)2]n by bis(3,5-dimethylpyrazol-1-yl)acetic acid and resulted in the target complex [Ru(bdmpza)(CO)(μ2-CO)]2 (6) in a yield of 30%. The constitution of the molecule is confirmed by elemental analysis as well as by ESI MS data in acetonitrile, which show a 100% peak at m/z 405.02 (100) + assigned to a [Ru(bdmpza)(CO)2] fragment and a small (4%) molecular ion peak at m/z 810.05. Due to the low solubility of 6 in all common deuterated solvents, only 1H NMR data could be obtained so far. As expected for the C2h-symmetric molecule depicted in Figure 3, only one set of signals is observed, with the methyl singlet signals observed at 2.35 (Me3) and 2.62 Figure 4. Spin density plot regarding the electrons forming the Ru− (Me5) ppm. The pyrazole CH proton is found at 6.04 ppm and Ru bond. the methine proton at 6.31 ppm. In theory at least three 56 isomeric forms of complex 6 might be possible: (I) terminal sets in the theoretical treatment. In order to achieve a μ μ correlation with observed spectra, a scaling factor of trans-CO/ 2-CO bridged, (II) terminal cis-CO/ 2-CO bridged, 56 (III) nonbridged. Apparently, according to the NMR data only approximately 0.96 has to be applied. Depending on the examined vibration, this factor differs slightly even in the same one of these possible isomeric forms seems to be present in 57 solution. This is in contrast to the case for [Ru(η5- molecule and is usually greater for lower energies. We were C H )(CO)(μ -CO)] ,whereanequilibriumofvarious especially interested in the two carbonyl vibrations, which were 5 5 2 2 −1 isomeric forms was reported.50,55 The bdmpza ligand exhibits predicted (unscaled) at 2078 cm (terminal CO) and at 1851 −1 − −1 cm−1 (μ -CO). This leads to expected vibrations at 1995 and its typical IR vibrations at 1673 cm (as-CO2 ) and 1559 cm 2 3 −1 (CN) as expected for κ coordination. The IR spectrum in 1777 cm . Both values agree well with the experimental data. In further agreement with the experimental data, the trans solution (CHCl3 solvent) is almost identical with that obtained −1 geometry of the bridged isomer of 6 was found to be the lowest in a KBr matrix. IR vibrations (CHCl3) at 1978 cm (terminal −1 in energy. The energy difference between the bridged and CO) and 1761 cm (μ2-CO) agree well with those reported! ! 5 nonbridged (Figure 5)Results species and Discussion was found to be rather small, for μ2-CO isomers of [Ru(η -C5H5)(CO)(μ2-CO)]2 (ν!(CO) ! −1 −1 (CHCl3 solvent) 2009 cm (terminal CO) and 1768 cm −1 (μ2-CO); ν(CO) (MeCN solvent) 1995 cm (terminal CO) −1 55b and 1775 cm (μ2-CO)). Thus, owing to the observed very strong μ2-CO vibration one μ2-CO isomer seems to dominate in the solid state as well as in solution. Nevertheless, a very weak shoulder around 2010 cm−1 and a weak signal at 1950 cm−1 might indicate traces of a nonbridged species. Due to the steric hindrance of the bdmpza ligands and in accord with DFT calculations (see below), the μ2-CO isomer cis-[Ru(bdmpza)- (CO)(μ2-CO)]2 (isomer II) with cis geometry of the terminal CO ligands seems to be thermodynamically disfavored. Thus, in accordance with the solid-state structure (Figure 3) trans- [Ru(bdmpza)(CO)(μ2-CO)]2 (6) (isomer I) is the main isomeric form. To elucidate the spectroscopic properties and the binding situation in [Ru(bdmpza)(CO)(μ2-CO)]2 (6) further, DFT calculations were performed for 6 starting from the X-ray structure determination data. The resulting geometry of the DFT calculations was almost identical with the geometry Figure 5. Calculated geometry of a nonbridged isomer of 6. of the X-ray structure determination. The spin density of the Figure 13. Calculated geometry of a nonbridged isomer of 12. two electrons forming the Ru−Ru bond is mainly located at the metal centers and the bridging carbonyl ligands (Figure 4). with ΔE = 22 kJ/mol in comparison to an energy difference of Preliminary studies by G. TÜRKOGLU revealed the promising potential of Surprisingly, the spin density plot does not resemble the ΔE = 45 kJ/mol between the cis and trans geometries. The low 2 [Ru(bdmpza)Cl(CO) ] (9) and [Ru(2,2-bdmpzp)Cl(CO) ] (10) as epoxidation catalysts, with a contour plots of two dz orbitals but the contour plots of dxy, energy2 difference toward the unbridged2 isomer implies a rather dxz, or dyz orbitals. This implies that the Ru−Ru bond isTON better for complexhigh possibility 9 up to of 20. finding[223] Even the higher nonbridged TON values isomer might in solution, be accessible by described as a π bond than as a σ bond. In order to verify the IR which may agree with the data of the IR spectra discussed signals of 6, DFT calculations on 6 were performed. It isoptimization well- above.of the react Theion strong conditions asymmetric or by applying IR vibrations soluble of iodosylbenzene the nonbridged derivatives as known for the chosen B3LYP/6-31G* DFT functionaloxidant. and CO were predicted (unscaled) at 2075 and 2047 cm−1, which basis set that calculated vibrational frequencies are typically should result in vibrations around 1992 and 1965 cm−1. overestimated in comparison to experimental data. TheseCurrently errors the complexExperiments [Ru(bpza)Cl(CO) regarding2] (13 the) is oxidationtested in cooperation of cyclohexene with the group of S. arise from the neglect of anharmonicity effects, incomplete mediated by complexes 3 and 4 were carried out in MÉNAGE as center for an artificial oxygenase. Therefore, complex 13 was incorporated into an incorporation of electron correlation, and the use of finite basis unstabilized, HPLC grade CH2Cl2 under a dinitrogen enzyme pocket and the isolated hybrid was employed in the oxidation of styrene yielding 2170 dx.doi.org/10.1021/om2009155 | Organometallics 2012, 31, 2166−2174 styrene glycol, which is not accessible by the complex or protein itself. Currently, the single crystal X-ray structure determination of the hybrid is solved and refined and the parameters of the catalysis are tuned for a greener reaction.
51 ! ! Results and Discussion ! !
4.3 Ruthenium Heteroscorpionate Complexes with Aminophenol Based Ligands
The oxidative ring cleavage of substituted aromatic compounds such as catechols and o-aminophenols is most commonly performed by mononuclear non-heme iron dioxygenases.[239-241] Some play important roles in human metabolism, for example in tryptophan degradation. 3-Hydroxyanthranilate (HAA) is O2-mediated cleaved by the HAA- 3,4-dioxygenase (HAD) and reacts to quinolinate (Scheme 36).[242-243]
NH2 NH2 CO2H - - non- - O2C OH O2C O2C O2 COOH enzymatic N HAD CHO - H2O
Scheme 36. Catalyzed reaction from 3-hydroxyanthranilate (HAA) to quinolinate.[242, 244]
In 2012 A. FIEDLER et al. reported the first synthetic intermediate of this enzyme in form of the Fe2+–ISQ (ISQ = iminobenzosemiquinonate) complex.[244] Reaction of the Tp based iron complex [(Ph2Tp)Fe(OBz)] with the sterically demanding aminophenol ligand 2-amino-4,6-di-
tBu tBu – 2 tert-butylphenol ( APH2; 2-amino-4,6-di-tert-butylphenolate = APH ) yields the κ coordinated complex [(Ph2Tp)Fe(2+)(tBuAPH)] which mimics the enzyme-substrate complex.[244] Reaction of this complex with 2,4,6-tri-tert-butylphenoxy radical (TBBP •) leads to an iron(II) complex bound to an ISQ radical.[244] The resulting Fe2+–SQ (SQ = semiquinone) complex is often invoked as intermediate for the mechanism of catechol dioxygenases although all other relevant models feature [Fe3+–catecholate]+ units.[245-247] Further one-electron oxidation using
Ag[SbF6] allows isolation of a cationic complex that shows an oxidation state that can be attributed to a [Fe3+–ISQ–]+ or [Fe2+–IBQ]+ complex (IBQ = iminobenzoquinonate).[244]
Recently T. PAINE et al. reported the first functional model for 2-aminophenol dioxygenases, namely APD (2-aminophenol-1,6-dioxygenase) and HAD.[248] The non-heme complex [(6-
2+ tBu Me3-TPA)Fe (4- HAP)](ClO4) (6-Me3-TPA = tris(6-methyl-2-pyridylmethyl)amine, tBuHAP = 2-amino-4-tert-butylphenol), which is readily available from a one-pot synthesis shows reactivity with dioxygen and formation of 4-tert-butyl-2-picolinic acid through C–C bond cleavage of 2-amino-4-tert-butylphenol.[248]
52
! ! Results and Discussion ! !
Due to the high sensibility of Fe2+ based heteroscorpionate complexes bearing aminophenol ligands it was decided to start from the commonly used precursor [Ru(bdmpza)Cl(PPh3)2] tBu (14). M. KECK synthesized during his master thesis a dark blue complex bearing the APH2 ligand. Due to the lack of a single crystal X-ray structure determination it was supposed from analytical data that the complex should be of the general formula [Ru(bdmpza)-
tBu ( ISQ)(PPh3)]Cl (Scheme 37). Strong antiferromagnetic spin-spin coupling might lead in this case to diamagnetic coupling in NMR spectroscopy allowing the observation of the imino proton at 14.19 ppm in the 1H NMR spectrum. It was discussed that two theoretical binding modes for the tBuAPH– could occur with the imino and hydroxo functionality positioned trans to the carboxylate anchor and one pyrazole unit and vice versa.
a) b) Me Me Me Me N N N N Me Me O O N O N N O N N N tBu Me Ru Me Me Ru Me O O K APH N N PPh PPh - Cl- O NH 3 HN O 3 Me Ru Me Ph3P PPh3 t Cl Bu tBu
tBu tBu
tBu Scheme 37. Synthesis of [Ru(bdmpza)( ISQ)(PPh3)]Cl (15A, 15B) by M. KECK and its supposed structures a) and b).
The high solubility of complex 15 in polar and nonpolar solvents led to difficulties in obtaining crystals suitable for a single crystal X-ray structure determination. Nevertheless, dissolving complex 15 in a hot mixture of CH2Cl2 and n-hexane, layered with pure n-hexane led to the formation of crystals.
The result of a single crystal X-ray structure determination shows that the predicted binding mode is not in agreement with the observed structure (Figure 14). Instead of a κ2 coordinated tBuISQ ligand a κ1 coordination of a possibly neutral tBuIBQ or monoanionic tBuISQ occurs, which is unprecedented in literature. The APH2 based ligand coordinates with the imino moiety trans to a pyrazole unit of the bdmpza ligand. A PPh3 and a chlorido ligand occupy the two remaining coordination sites and the absence of counter ions indicates the formation of a neutral complex. 53 ! ! Results and Discussion ! !
b a c O2 C1 N12 N22
O1 N11 N21 Ru C66 C65 N61 C61 Cl1 C64 P1 H61 C63 C62
O62
tBu tBu Figure 14. Molecular structure of [Ru(bdmpza)Cl( ISQ/ IBQ)(PPh3)] (15). Thermal ellipsoids are drawn at the 50% probability level. Most hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.1495(17), Ru–N(21) = 2.098(2), Ru–O(1) = 2.1037(14), Ru–P(1) = 2.3318(6), Ru– Cl(1) = 2.3956(6), Ru–N(61) = 1.962(2), N(61)–C(61) = 1.310(3); N(11)–Ru–N(21) = 85.29(7), O(1)–Ru– N(21) = 85.72(7), O(1)–Ru–N(11) = 85.57(6), O(1)–Ru–P(1) = 85.76(4), P(1)–Ru–Cl(1) = 99.45(2), P(1)–Ru– N(61) = 87.43(5), O(1)–Ru–N(61) = 97.17(7), N(11)–Ru–P(1) = 170.81(5), N(21)–Ru–Cl(1) = 92.35(5), Cl(1)– Ru–N(61) = 84.39(6), Ru–N(61)–C(61) = 138.72(17).
For “non-innocent” APH2 ligands several oxidation states are known which in conclusion allow the interaction with the metal center in form of redox chemistry.[249] Starting from the deprotonated tBuAP2– the first one electron oxidation leads to the aforementioned anionic tBuISQ radical, which in the next oxidation step forms the tBuIBQ compound (Scheme 38).[249]
tBu tBu tBu O- - e- O - e- O + e- + e- tBu NH- tBu NH tBu NH tBuAP2- tBuISQ tBuIBQ
Scheme 38. Forms of the tert-butyl substituted aminophenol ligand seperated by one-electron redox steps.[249]
54 ! ! Results and Discussion ! !
+ Bond length [Å] 15 16 [Ru(acac)2(ISQ)] [RuCl(terpy)(ISQ)]
Ru–N(61) 1.962(2) 1.962(5) 1.906(3) 1.942(8)
N(61)–C(61) 1.310(3) 1.293(8) 1.340(4) 1.312(12)
C(61)–C(62) 1.498(3) 1.485(9) 1.439(4) 1.433(13)
C(62)–O(62) 1.231(2) 1.221(9) 1.291(4) 1.270(11)
C(62)–C(63) 1.470(3) 1.441(11) 1.424(5) 1.416(13)
C(63)–C(64) 1.350(3) 1.280(11) 1.363(6) 1.322(13)
C(64)–C(65) 1.449(3) 1.425(11) 1.409(7) 1.446(15)
C(65)–C(66) 1.347(3) 1.351(10) 1.345(6) 1.377(14)
C(66)–C(61) 1.432(3) 1.406(9) 1.411(5) 1.433(13)
[250] Table 4. Selected bond lengths of the ruthenium iminoquinone complexes 15, 16, [Ru(acac)2(ISQ)] and [251] [RuCl(terpy)(ISQ)]ClO4.
Bond length [Å] 15 16 [Ru(bdmpza)Cl(PPh3)2] [Ru(bdmpza)Cl2(PPh3)]
Ru–N(11) 2.1495(17) 2.133(5) 2.199(4) 2.184(3)
Ru–N(21) 2.098(2) 2.102(5) 2.173(4) 2.109(3)
Ru–O(1) 2.1037(14) 2.088(4) 2.133(3) 2.045(3)
Ru–Cl(1)/Cl(2) 2.3956(6) 2.3835(17) 2.4157(17) 2.346(2) / 2.3581(19)
Ru–P1/P2 2.3318(6) 2.3300(18) 2.3555(17) / 2.3688(18) 2.3715(18)
Table 5. Selected bond lengths of the ruthenium iminoquinone complexes 15 and 16 and closely related [168] heteroscorpionate complexes [Ru(bdmpza)Cl(PPh3)2] (14) and [Ru(bdmpza)Cl2(PPh3)].
In comparison with literature known [Ru3+–ISQ] complexes the bond lengths of the ISQ ligands are in good agreement, although the alternation between located double and single bonds is more pronounced for complex 15 (Table 4).[250-251] In addition the oxygen–carbon bond is shortened due to the lack of interaction with the ruthenium center. To further understand the oxidation state of the metal center, a look at the heteroscorpionate ligand is useful. The closely related compounds [Ru(bdmpza)Cl(PPh3)2] (14) and [Ru(bdmpza)-
Cl2(PPh3)] show ruthenium(II) and ruthenium(III) centers, respectively, which in comparison to complex 15, highlight the proposed ruthenium(III) structure (Table 5).[168] Especially the bond Ru–N(11) which is positioned trans to a PPh3 ligand and thus not directly influenced by ligand exchange shows similar values for 15 and the ruthenium(III) complex. This
55 ! ! Results and Discussion ! ! emphasizes the assumption of a [Ru3+–ISQ] compound, although they do not allow a final decision between an ISQ or IBQ ligand. Questionable remains the reaction pathway as the metal and the ligand both undergo one-electron oxidation in absence of an oxidant. Possibly contamination with oxygen might play a key role and lead to the low reported yields.
Hence it was decided to synthesize the analogous complex based on unsubstituted
[250] [251] 2-aminophenol (APH2) similar to [Ru(acac)2(ISQ)] and [RuCl(terpy)(ISQ)]ClO4.
Deprotonation of APH2 with potassium tert-butylate followed by addition of [Ru(bdmpza)Cl-
(PPh3)2] (14) at room temperature led to the formation of a dark solution (Scheme 39). After two chromatography steps the complex was obtained as a dark blue solid in extremely low yields.
Me Me Me Me N N N N O O O O t N N N N HO NH2 1. KO Bu Me Ru Me or Me Ru Me 2. 14 NH NH O O THF Ph3P Cl Ph3P Cl
16 (IBQ) 16 (ISQ)
Scheme 39. Synthesis of ISQ or IBQ complex [Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16).
In accordance with the expected structure ESI-MS experiments showed the presence of the molecular ion (m/z 753.12 (5%) M+) and the closely related sodium adduct (m/z 742.15 (100%) [M – Cl + Na]+). The 13C NMR and 1H NMR spectrum show the pattern of an asymmetric [Ru(bdmpza)] fragment with four independent signals for the methyl substituents. The imino proton results in a signal at 14.77 ppm in the 1H NMR spectrum. The carbonyl moiety of the ISQ/IBQ ligand gives rise to a signal at 171.3 ppm in the 13C NMR spectrum indicating a similar binding motif as 15 with an uncoordinated keto moiety. The lower solubility of 16 in nonpolar solvents in comparison to 15 allows crystallization from CH2Cl2 solution layered with n-hexane.
The result of a single crystal X-ray structure determination shows that the previously observed κ1 binding motif also occurs for the sterically less demanding ISQ/IBQ ligand. The arrangement around the ruthenium center is similar to 15 with the imino moiety of the
ISQ/IBQ ligand positioned trans to one pyrazole donor forcing the PPh3 ligand in trans
56 ! ! Results and Discussion ! !
position of the second pyrazole donor and the remaining chlorido ligand trans to the carboxylate anchor (Figure 15).
a b c
N12 N22
O2
N11 O1 N21 C65 C66 Ru Cl
N61 C62 C64 C61 H61 P1
C63 O62
Figure 15. Molecular structure of [Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16). Thermal ellipsoids are drawn at the 50% probability level. Most hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(21) = 2.102(5), Ru–N(11) = 2.133(5), Ru–O(1) = 2.088(4), Ru–P(1) = 2.3300(18), Ru– Cl(1) = 2.3835(17), Ru–N(61) = 1.962(5), N(61)–C(61) = 1.293(8); N(11)–Ru–N(21) = 84.9(2), O(1)–Ru– N(21) = 86.4(2), O(1)–Ru–N(11) = 85.96(18), O(1)–Ru–P(1) = 85.26(12), P(1)–Ru–Cl(1) = 99.56(6), P(1)–Ru– N(61) = 88.53(16), O(1)–Ru–N(61) = 97.9(2), N(11)–Ru–P(1) = 170.61(14), N(21)–Ru–Cl(1) = 91.18(18), Cl(1)–Ru–N(61) = 84.06(16), Ru–N(61)–C(61) = 137.9(5).
The bond lengths in the ISQ/IBQ ligand of complex 16 are listed in Table 4 and are in good agreement with the closely related complex 15 and especially the two unsubstituted ISQ/IBQ
complexes by G. LAHIRI et al.[250-251] However, especially the double bond character of C(63)– C(64) is more pronounced with a bond length of 1.280(11) Å for 16 compared to 1.350(3) Å
tBu tBu for [Ru(bdmpza)Cl( ISQ/ IBQ)(PPh3)] (15). The comparison with the ruthenium(II) and
ruthenium(III) complexes [Ru(bdmpza)Cl(PPh3)2] (14) and [Ru(bdmpza)Cl2(PPh3)] (Table 5) indicates that the complex can best be described as [Ru3+–ISQ] due to the shortened ruthenium nitrogen bonds between the bdmpza ligand and the ruthenium center indicating a ruthenium(III) center (2.133(5) Å and 2.102(5) Å for 16 in comparison to 2.184(3) Å and
2+ 2.109(3) Å for [Ru(bdmpza)Cl2(PPh3)]), although a [Ru –IBQ] system can not be ruled out. 57 ! ! Results and Discussion ! !
4.4 Carbon-rich Ruthenium Allenylidene Complexes
Parts of this chapter have been published:
Strinitz, F.; Waterloo, A.; Tucher, J.; Hübner, E.; Tykwinski, R. R.; Burzlaff, N., Eur. J. Inorg. Chem. 2013, 5181-5186.
Starting from the previous results of the BURZLAFF group concerning the formation of carbene, vinylidene and allenylidene complexes and their reaction behavior it was decided to investigate the possible substitution patterns of the propargyl alcohols employed.[61, 189]
As mentioned in chapter 2.5 only two structural isomers can be observed for
[Ru(bdmpza)Cl(PPh3)2] (14) based cumulenylidene complexes. For easy nomenclature the isomer with the cumulenylidene moiety trans to the pyrazole unit is indicated with “A” and the isomer with the cumulenylidene moiety trans to the carboxylate anchor with “B”. In a similar way the bdmpza ligand is numbered for NMR and single crystal X-ray structure determination purposes. The numbering is dependent on the position of the PPh3 ligand and follows the depicted scheme (Scheme 40).
Me5´ Me5 N N H4´ O H4 N ON Me3´ Ru Me3 Ph P Cl R 3
Scheme 40. Numbering scheme used for cumulenylidene complexes.
58 ! ! Results and Discussion ! !
4.4.1 Sterically Demanding Diphenyl Allenylidene Complexes
Typically the straight forward synthesis of ruthenium allenylidene complexes following Selegue´s route starts from substituted propargyl alcohols leading to the dissociation of water from the intermediary hydroxyvinylidene complexes. Depending on the used metal fragment, the dissociation of water requires the addition of catalytical amounts of acid, which allows the isolation of the labile vinylidene species. Nevertheless, for the facially coordinating bdmpza ligand, it has been observed that the intermediary vinylidene complexes can be detected via 1H NMR due to the characteristic vinylidene proton but the complex cannot be isolated and reacts directly to the allenylidene complex.[61] P. DIXNEUF et al. have previously shown that a reversible addition of sodium methoxide to the cationic allenylidene complex trans-[(dppm)2-
ClRu(═C═C═CPh2]PF6 yields the corresponding neutral alkynyl complex trans-[(dppm)2Cl- [252] Ru(–C≡C–CPh2(OMe)]. In an attempt to synthesize an isolable vinylidene complex based on [Ru(bdmpza)Cl(PPh3)2] (14) it was decided to start from the 3,5-di-tert-butyl substituted methoxy ether of the conventional used diphenyl propargyl alcohol. This compound has recently been shown to be an effective building block for forming stabilized organic cumulenes with up to ten carbon atoms.[253] Furthermore, the presence of the ether group might enhance the formation of the vinylidene complex due to the reduced leaving potential of the methanol unit in comparison to the free hydroxyl group.
The synthesis of the intended neutral vinylidene complex started from [Ru(bdmpza)Cl(PPh3)2] (14) and excess propargyl alcohol 1,1-bis-(1,3-di-tert-butylphenyl)-1-methoxy-2-propyne in THF (Scheme 41). Initially, no apparent color change was observed. After 3 d, however, a strong purple color was visible and the formation of the allenylidene complex
t [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19A, 19B) was completed by heating for 4 h under reflux. Due to the facial coordinating motif of the bdmpza ligand, the formation of two structural isomers was observed, as has been reported previously.[61] The relatively high stability (no degradation over days was observed) allowed the separation via column chromatography under aerobic conditions affording a purple (19A) and a red isomer (19B). 13C NMR spectra revealed for 19B characteristic signals for a ruthenium allenylidene complex
2 at 314.7 ppm (d, JCP = 18.3 Hz, Cα), 234.6 ppm (Cβ) and 152.4 ppm (Cγ) for the allenylidene unit, as well as a singlet in the 31P NMR spectrum at 34.5 ppm.
59 ! ! Results and Discussion ! !
H Me Me N N O t OMe t N O N + Bu Bu Me Ru Me Cl Ph3P PPh3 tBu tBu 14 Me Me N N O N O N Me Me 17 Me Ru Me N N O N O N Ph P Cl C 3 C H OMe Me Ru Me tBu C tBu Cl C Ph3P O 18A tBu tBu
Me Me Me Me N N N N O O N O N N O N Me Ru Me tBu Me Ru Me Ph P Cl C Ph P C Cl 3 C + 3 C C tBu tBu C tBu
tBu tBu tBu tBu 19A 19B
Me Me N N O N O N Me Ru Me Ph P C Cl 3 O 18B
t Scheme 41. Synthesis of ruthenium vinylidene intermediate [Ru(bdmpza)Cl(═C═CH(COMe(Ph Bu2)(PPh3)] (17), carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] (18A, 18B) and allenylidene complex t [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19A, 19B).
60 ! ! Results and Discussion ! !
For compound 19A the 13C NMR spectrum revealed strong contamination with the carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] (18A, carbonyl trans to pyrazole), which can be formed by oxygen induced bond cleavage of the vinylidene intermediate as has been shown
[61] previously for [Ru(bdmpza)Cl(═C═CHPh)(PPh3)]. Unfortunately, all attempts to avoid formation of 18A during synthesis or separation of 19A via column chromatography provided only impure product. Nevertheless, the assignment of the two structural isomers A and B to the respective symmetry and positions was accomplished based on comparisons to previously reported two-dimensional NMR experiments (ROESY) and APT 13C NMR measurements.[61] Namely, type B complexes show cross-peaks between the methyl substituents in the 3- and 3´ positions with the aryl protons of the allenylidene moiety in the ROESY spectrum, which indicate an arrangement trans to the carboxylate anchor.[61]
Cyclic voltammetric analyses were performed on the precursor [Ru(bdmpza)Cl(PPh3)2] (1) and on the resulting allenylidene complex 19B. The exhibited electrochemical properties are summarized in Chapter 8.2. The reversibility of the redox processes shows strong dependence on the solvent used, as voltammograms recorded in acetonitrile lead to irreversible oxidations and reductions indicating side reactions of the allenylidene complexes with acetonitrile. The
n voltammograms recorded in dichloromethane with Bu4NPF6 (0.1 M) as electrolyte and referenced to the ferrocene/ferrocenium couple as internal standard at a scan rate of 100 mV/s feature exclusively reversible and quasi-reversible processes. For the used precursor
[Ru(bdmpza)Cl(PPh3)2] (14) one reversible oxidation at 394 mV can be observed, which is attributed to the Ru(II)/Ru(III) couple. For the ferrocene/ferrocenium couple literature reports a peak separation of 78 mV (83 mV in our setup) in dichloromethane,[254] which is a good indication that the peak separation of 73 mV and the peak current ratio ipa/ipc = 0.80 for 14 confirm a reversible one-electron oxidation. For the first ruthenium allenylidene complex
t [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19B) two quasi-reversible redox processes can be observed. The oxidation of the ruthenium center happens at a lower potential of 265 mV compared to 14, indicating a possible electron releasing effect of the used allenylidene ligand in comparison to the PPh3 ligand. The reduced peak current ratio indicates however, that the reversibility is lowered in comparison to 14. A second redox process at –1631 mV can be attributed to the quasi-reversible reduction (ipa/ipc = 0.67) of the allenylidene moiety as reported previously for the systems [Cl(dppe)2Ru(═C═C═CPh2)]PF6 (–1.03 V) and [Cl(16- [124, 255] TMC)Ru(═C═C═CPh2)]PF6 (–1.27 V). In comparison it is obvious that the two redox
61 ! ! Results and Discussion ! ! couples of the neutral bdmpza allenylidene complex 19B are more cathodic in comparison to the aforementioned cationic allenylidene complexes (Δ = 0.60 V/0.36 V).
The intense color of the allenylidene complexes can best be characterized via UV/Vis absorption spectroscopy. Hence the comparison with the previously reported bdmpza based allenylidene complexes [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)] and [Ru(bdmpza)Cl-
(═C═C═C(tol)2)(PPh3)] is a good starting point. For type B isomers absorption maxima of [61] 495 and 507 nm have been reported for solutions in CH2Cl2. The closely related complex t [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19B) shows a maximum at 506 nm with a molar extinction coefficient of approximately 13000 L mol–1cm–1 (Figure 16). This transition was assigned to a metal-to-ligand charge-transfer (MLCT) for the diphenyl and ditolyl substituted allenylidene complexes in literature.[61] However, newer calculations performed for complexes within this work indicate, that this transition corresponds to a metal-perturbed π-π* transition.[256] A further transition that can be observed in the NIR region at 1024 nm with an extremely low extinction coefficient indicating a forbidden transition, which might belong to the MLCT in which the HOMO–1, HOMO and LUMO have been involved for the pentacenequinone based allenylidene complexes (Figure 17).[256] Due to lack of a single crystal X-ray structure determination no TD-DFT calculations were performed on this complex and no definite answer can be given on this topic.
62 ! ! Results and Discussion ! !
20000
15000 ] .1 (cm
.1 10000 ([L(mol ε
5000
0 400 600 800 1000 1200 1400 1600
Wavelength([nm]
Figure 16. Absorption spectrum of 19B in CH2Cl2.
200
150 ] .1 (cm
.1 100 ([L(mol ε
50
0 800 1000 1200 1400 1600 Wavelength([nm]
Figure 17. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 19B.
63 c ! ! b a Results and Discussion ! !
O2 C1 N12 N22 C2 N21 O1 N11
Ru1
C3 P1 Cl1 O3
Figure 18. Molecular structure of [Ru(bdmpza)Cl(CO)(PPh3)] (18B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.156(3), Ru–N(21) = 2.082(3), Ru–O(1) = 2.119(2), Ru–P(1) = 2.3360(10), Ru– Cl(1) = 2.3880(11), Ru–C(3) = 1.923(5), C(3)–O(3) = 1.009(5); N(11)–Ru–N(21) = 82.68(11), O(1)–Ru– N(11) = 85.60(10), O(1)–Ru–N(21) = 87.15(10), O(1)–Ru–P(1) = 86.27(7), P(1)–Ru–Cl(1) = 90.05(4), P(1)– Ru–C(3) = 95.27(11), O(1)–Ru–C(3) = 177.34(13), N(21)–Ru–P(1) = 97.08(8), N(11)–Ru–Cl(1) = 89.87(8), Cl(1)–Ru–C(3) = 87.26(11), Ru–C(3)–O(3) = 176.0(4).
Attempts to obtain crystals of 19B suitable for X-ray diffraction by layering a solution in dichloromethane with n-hexane leads, within several weeks, to bond cleavage of the allenylidene unit with conservation of the relative geometry, providing complex 18B as illustrated in Figure 18. In comparison to the previously reported carbonyl complex 18A, the carbonyl ligand in 18B is in trans position to the carboxylate. Thus, the chlorido and triphenylphosphine ligands are in trans position to the pyrazole units. This observation is unexpected since the direct carbonylation of [Ru(bdmpza)Cl(PPh3)2] (14) and decomposition of the resulting vinylidene complexes leads exclusively to the carbonyl complex 18A with the carbonyl trans to a pyrazole.[61] The ruthenium(II) center is facially coordinated by the bdmpza ligand resulting in a slightly distorted octahedral geometry caused by the rather rigid and strained coordination geometry of the heteroscorpionate ligand. The Ru–C(3) (1.923(5) Å) bond is slightly elongated and C(3)–O(3) (1.009(5) Å) contracted in comparison to the other structural isomer 18A (Ru–C(3) = 1.831(5) Å, C(3)–O(3) = 1.151(6) Å) as a
64 ! ! Results and Discussion ! ! result from the trans-orientation of the carboxylate group. This is in contrast to the pyrazolyl donor, which is a σ and π donor as well as a π acceptor and shows no trans influence, as previously discussed and supported by DFT calculations for the dissociation energies of N,N,O ligands.[173] This observation suggests that the steric demand of the four tert-butyl groups reduces the stability in comparison to the analogous unsubstituted diphenyl allenylidene complex, i.e., substituted with only two phenyl rings.
65 ! ! Results and Discussion ! !
4.4.2 Fluorene Based Allenylidene Complexes
Closely related to the diphenyl allenylidene complexes are systems bearing a fluorene group on Cγ. Fluorene based allenylidene complexes have previously shown to inhibit the rearrangement of the allenylidene moiety into the corresponding indenylidene complex.[167]
6 NMR spectroscopic experiments have shown that [(η -p-cymene)RuCl(═C═C═(FN))(PCy3)]- OTf (FN = fluorenyl) reacts upon addition of HOTf to the alkenylcarbyne, but no further transformation could be observed.[167] Furthermore polyfluorenes are organic electro- luminescent materials that have been applied to devices in photonics and optoelectronics.[257- 259] Following the route described above, addition of excess amounts of 9-ethynylfluoren-9-ol to [Ru(bdmpza)Cl(PPh3)2] (14) led to the formation of a deep purple solution (Scheme 42). The increased stability of the obtained structural isomers allowed separation via column chromatography under aerobic conditions yielding a purple (20A, allenylidene trans to pyrazole) and a red isomer (20B, allenylidene trans to carboxylate).
Me Me N N O N O N Me Me Me Me Me Ru Me N N N N O O N O N N O N Ph3P Cl PPh3 14 Me Ru Me Me Ru Me + Ph P Cl C + Ph P C Cl THF 3 C 3 H C C C OH
20A 20B
Scheme 42. Synthesis of bdmpza based ruthenium allenylidene complexes [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (FN = fluorenyl) (20A, 20B).
For 20A the characteristic signals for the allenylidene chain are observed in the 13C NMR
2 3 spectrum at 300.6 (d, JC,P = 27.6 Hz, Cα), 236.4 (d, JC,P = 4.6 Hz, Cβ) and 141.0 ppm (Cγ) with doublets for Cα and Cβ caused by coupling with the phosphorus atom of the triphenylphosphine ligand. Furthermore, the IR spectrum shows an intense band at 1910 cm–1 in the IR spectrum corresponding to the cumulenylidene ligand. The 31P NMR spectrum
66 ! ! Results and Discussion ! ! consists of one singlet at 34.6 ppm and ESI-MS experiments showed the presence of the protonated monocationic species (m/z 825.16 (100%) MH+). Similar spectroscopic values are
2 obtained for the second isomer 20B with signals at 314.4 (d, JC,P = 19.3 Hz, Cα), 256.2 (Cβ) 13 and 141.6 ppm (Cγ) in the C NMR spectrum (P–C coupling observable for Cα), while the 31P NMR spectrum shows one singlet at 30.9 ppm, which is shifted upfield in comparison to 20A. The IR spectrum shows the cumulenic stretch at 1903 cm–1 a slightly lower value than that for 20A and the ESI-MS experiments reveal the main observable signal that is consistent with the protonated monocationic species (m/z 825.16 (100%) MH+). The assignment of the geometries was in accordance to the previous synthesized bdmpza based allenylidene complexes and could be verified by single crystal X-ray structure determinations of both isomers. Crystals were obtained from solutions in CH2Cl2 layered with n-hexane. 20A and 20B represent the first single-crystal X-ray structure determinations of fluorene based allenylidene complexes.[107, 166-167, 252, 260-261] Complex 20A crystallizes as an racemic mixture
(space group Pbca) as [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] × H2O with one water molecule bound via a hydrogen bond to the carbonyl moiety of the carboxylate unit (Figure 19). The molecular structure exhibits a slightly distorted octahedral geometry at the Ru(II) center with the allenylidene positioned trans to a pyrazole donor, the triphenylphosphine trans to the second pyrazole donor and the chlorido ligand trans to the carboxylate anchor. In comparison to the diphenyl allenylidene complex [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)], the bdmpza ligand of 20A shows only slight deviations.[61] The Ru–C(61) bond is with 1.865(3) Å similar
[61] to the analogous [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)] (1.886(5) Å) and the octahedral Tp
3 [121] ruthenium allenylidene complex [Ru(κ -HB(pz)3)(═C═C═CPh2)(PPh3)2]PF6 (1.889(3) Å) but considerably longer than in pentacoordinated 16 VE ruthenium allenylidene complexes
[95] like [RuCl2(═C═C═CPh2)(PCy3)2] (1.794(11) Å). The allenylidene chain deviates slightly from the linear geometry (∠Ru–C(61)–C(62) = 175.1(3)°, ∠C(61)–C(62)–C(63) = 172.7(3)°) with the fluorenyl moiety remaining in plane with the C═C═C moiety.
67 c ! b ! a Results and Discussion ! !
C1 O2 N12 N22 C2 N11 N21 O1
Ru1
C61 Cl1 P1 C62 C64 C63 C65 C67 C66
Figure 19. Molecular structure of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and one water molecule have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.172(2), Ru–N(21) = 2.231(2), Ru–O(1) = 2.094(2), Ru– P(1) = 2.3121(9), Ru–Cl(1) = 2.3552(9), C(63)–C(67) = 1.472(4), C(63)–C(64) = 1.470(4), C(64)– C(65) = 1.406(4), C(65)–C(66) = 1.466(5), C(66)–C(67) = 1.407(4), Ru–C(61) = 1.865(3), C(61)– C(62) = 1.247(4), C(62)–C(63) = 1.352(4); N(11)–Ru–N(21) = 83.05(9), O(1)–Ru–N(11) = 86.32(9), O(1)–Ru– N(21) = 82.43(9), O(1)–Ru–P(1) = 92.72(6), P(1)–Ru–Cl(1) = 92.09(3), P(1)–Ru–C(61) = 85.66(9), O(1)–Ru– C(61) = 92.39(11), N(21)–Ru–P(1) = 99.15(7), N(11)–Ru–Cl(1) = 89.19(7), Cl(1)–Ru–C(61) = 96.26(9), Ru– C(61)–C(62) = 175.1(3), C(61)–C(62)–C(63) = 172.7(3).
As has been described for the structural related butatriene 4-(9H-fluoren-9-ylidene)-2-
[262] methylbuta-2,3-dienal (COH(CH3)C═C═C═(FN)), the bond lengths of the five-membered ring of the fluorenyl unit of 20A show less bond length alternation than the parent fluorenone,[263] which indicates a strong delocalization of the electron density from the allenylidene moiety to the fluorenyl unit. Also noticeable are strong solid-state π-π stacking interactions between two neighboring fluorenyl units (Figure 20), with an interplanar distance of 3.45 Å as calculated from the least-squares plane generated from the carbon atoms of one fluorenyl moiety to the plane of its neighbor.
68 ! ! Results and Discussion ! !
Bond length [Å] 20A 20B Fluorene COH(CH3)C═C═C═(FN)
C63–C64 1.470(4) 1.469(7) 1.486 1.469
C64–C65 1.406(4) 1.408(7) 1.390 1.390
C65–C66 1.466(5) 1.463(8) 1.475 1.471
C66–C67 1.407(4) 1.407(7) 1.390 1.404
C67–C63 1.472(4) 1.466(7) 1.486 1.465
Table 6. Selected bond lengths of the five membered rings of the ruthenium allenylidene complexes 20A and [262-263] 20B, fluorene and the structural related butatrien COH(CH3)C═C═C═(FN).
a) b)
Figure 20. π–π stacking interactions between two molecules of 20A a) top view and b) side view.
69 ! ! Results and Discussion ! b ! a
c
O2 C1 N12 C2 N22 N11 O1 N21
Ru1
C61 C64 P1 Cl1 C62 C63 C65
C67 C66
Figure 21. Molecular structure of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules CH2Cl2 have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.146(4), Ru–N(21) = 2.081(4), Ru–O(1) = 2.144(3), Ru– P(1) = 2.3552(12), Ru–Cl(1) = 2.4077(11), C(63)–C(67) = 1.466(7), C(63)–C(64) = 1.469(7), C(64)– C(65) = 1.408(7), C(65)–C(66) = 1.463(8), C(66)–C(67) = 1.407(7), Ru–C(61) = 1.855(5), C(61)– C(62) = 1.247(7), C(62)–C(63) = 1.363(7); N(11)–Ru–N(21) = 83.54(15), O(1)–Ru–N(11) = 85.55(13), O(1)– Ru–N(21) = 86.49(13), O(1)–Ru–P(1) = 85.75(9), P(1)–Ru–Cl(1) = 88.10(4), P(1)–Ru–C(61) = 95.27(15), O(1)–Ru–C(61) = 178.55(16), N(21)–Ru–P(1) = 98.00(11), N(11)–Ru–Cl(1) = 90.02(11), Cl(1)–Ru– C(61) = 89.85(14), Ru–C(61)–C(62) = 175.7(4), C(61)–C(62)–C(63) = 177.2(5).
The second structural isomer 20B shows solid-state characteristics similar to that of 20A, including a distorted octahedral geometry (Figure 21). Compound 20B crystallizes in space group P–1 as a racemic mixture. The chlorido and PPh3 ligand are now positioned trans to pyrazole donors, placing the allenylidene unit trans to the carboxylate anchor. Therefore, the respective bond lengths differ slightly in comparison to isomer 20A. For example, there is shortening of the Ru–C(61) bond to 1.855(5) Å and a similar contraction of the Ru–N(11) bond, which can be explained by the reduced trans influence in this structural isomer because of the π accepting pyrazole and allenylidene ligand are no longer positioned trans to each other. Additionally, the allenylidene chain is slightly less distorted from linearity than in 20A
(∠Ru–C(61)–C(62) = 175.7(4)°, ∠C(61)–C(62)–C(63) = 177.2(5)°). This can be explained by the different packing motif in the solid state. The change in the relative positions around the ruthenium center also leads to reduced distances between the fluorenyl moiety and one phenyl ring of the triphenylphosphine ligand of the complex. This close proximity of the phenyl rings
70 ! ! Results and Discussion ! ! appears to hinder the π-π stacking interaction between two neighboring fluorenyl units in the solid state, which also seems to result in the smaller angles in ∠Ru–Cα–Cβ and ∠Cα–Cβ–Cγ of 20A.
The fluorene based allenylidene complexes [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A, 20B) show a reversible oxidation at 389 mV/371 mV indicating a positive shift in peak potential in comparison to 19B (Chapter 8.2). Interesting is the appearance of two redox processes at negative voltages. While the process at –1273 mV (20A, 20B) is again attributed to the reduction of the allenylidene moiety and appears more anodic in comparison to 19B, a second quasi-reversible/reversible process appears at –1932 mV (20A) and –1937 mV (20B), that we assign to the reduction of the fluorenyl moiety. Although the position of the allenylidene moiety trans to the pyrazole or carboxylate moiety strongly influences the physical and chemical properties of the complex no obvious differences in electrochemical properties could be observed for these two structural isomers.
The UV/Vis absorption spectra of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A, 20B) recorded in CH2Cl2 show several intense absorptions (Figure 22). The strong absorptions below 400 nm can be attributed to ligand centered π–π* transitions involving the bdmpza and PPh3 ligand. As mentioned previously the strong absorption at 546 nm (20A) or 517 nm (20B) with molar
–1 –1 * extinction coefficients around 15000 L mol cm correspond to a metal-perturbed π-π transition of the allenylidene moiety. Again weak transitions can be observed in the NIR region for both complexes with a signal at 1053 nm with a shoulder at 919 nm for 20B (Figure 23). For 20A, two distinct signals at 1201 nm and 944 nm can be observed. These transitions can be assigned to HOMO → LUMO and HOMO–2 → LUMO excitations, which are MLCT transitions (Table 7).
Observed values Calculated values
Compound Wavelength Absorption Wavelength Transition dipole Transition [nm] coefficient [nm] moment [debye] [M–1 cm–1] 20A 1053 226 906 0.12 HOMO ! LUMO 919 175 813 0.54 HOMO–2 ! LUMO Table 7. Calculated and measured transitions for 20A in the NIR region.
71 ! ! Results and Discussion ! !
20000
15000 ] .1 (cm .1 10000 ([L(mol ε
5000
0 400 600 800 1000 1200 1400 1600 Wavelength([nm]
Figure 22. Absorption spectrum of 20A (black) and 20B (grey) in CH2Cl2.
200 ] -1
'cm * -1
100 '[L'mol ε
0 800 1000 1200 1400 1600 Wavelength'[nm]
Figure 23. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 20A (black)
and 20B (grey); signal caused by CH2Cl2 is indicated by *.
72 ! ! Results and Discussion ! !
To further understand the absorption spectra TD-DFT calculations (time-dependent DFT) have been performed by E. HÜBNER for complex 20A that explain the absorptions at the edge of the NIR region. Especially, the HOMO → LUMO and HOMO–2 → LUMO transitions with low transition dipole moments of 0.12 and 0.54 debye seem to correspond to forbidden MLCT transitions. The calculated geometries emphasize that the LUMO is delocalized over the ruthenium center as well as the entire allenylidene moiety and the fluorenyl unit, whereas the HOMO and HOMO–2 are mainly located on the ruthenium center and Cα and Cβ (Figure 24). Furthermore, the calculated absorptions are in good agreement with the measured values (Table 7).
LUMO HOMO
HOMO–1 HOMO–2
Figure 24. Orbital diagrams of the LUMO (–2.9 eV), HOMO (–5.2 eV), HOMO–1 (–5.3 eV) and HOMO–2
(–5.4 eV) of [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A).
73 ! ! Results and Discussion ! !
4.4.3 Anthraquinone Based Allenylidene Complexes
Although heteroatom substituted allenylidene complexes based on 4,5-diazafluorene[126-127] and cyclopentadithiophene[128] have been reported, little is known about allenylidene complexes with larger polyaromatic substituents. To date, only few complexes are discussed in literature, such as, for example, trans, trans-[(dppe)2RuCl(C═C═C(bianth)C═C═C)ClRu-
(dppe)2](OTf)2 that is based on the extended conjugated system [9,9′]bianthracenylidene- 10,10′-dione are discussed in literature.[113] Notably in this system, the close proximity of the protons of two anthrone units of the bianthrone moiety results significant strain and a non- planar organic spacer. For further studies on the π-π stacking interactions between polyaromatic allenylidene units and electron transfer properties between the ruthenium(II) center and the organic substituents it was decided to look into anthraquinone based allenylidene complexes.
The use of anthraquinone derivatives is manifold ranging from the anthraquinone oxidation process for hydrogen peroxide production to dye precursors.[264-265] A recent highlight was the construction of a metal-free organic-inorganic aqueous flow battery by B. HUSKINSON and M.
MARSHAK et al.[266] 9,10-Anthraquinone-2,7-disulphonic acid (AQDS) undergoes rapid and reversible two-electron two-proton reduction in sulfuric acid. Combination of the couple
– quinone/hydroquinone with the couple Br2/Br with glassy carbon electrodes allows the formation of promising flow batteries for electrical energy storage at greatly reduced cost.[266]
O. WENGER et al. recently published a bpy (bpy = 2,2´-bipyridine) based ruthenium complex bearing an anthraquinone moiety in its periphery.[267] The thermodynamics and kinetics of the
2+ intramolecular electron transfer between the [Ru(bpy)3] core and the anthraquinone unit 2+ linked via one up to three xylene linkers in the complex [Ru(bpy)2(bpy–xyn–AQ)] (xy = p- xylene, n = 0-3) was investigated. It was shown that electron transfer between the ruthenium core and the anthraquinone unit can be triggered by photoexcitation leading to the charge separated state. The solvent influence on the electron transfer indicates a finite proton density transfer rather than a full PCET (proton coupled electron transfer).[267] This redox behavior shows similarities to the electron transfer cascade in photosynthetic reaction centers of bacteria.[268]
For the formation of the first anthraquinone based allenylidene complex the anthraquinone (AQ) based 10-ethynyl-10-hydroxyanthracen-9-one (24) is promising. The required precursor 74 ! ! Results and Discussion ! !
24 is known to the literature, however, an appealing high yield synthesis is missing.[269-271] The classic approach to 24 begins with the formation of a lithium acetylide, via reaction of gaseous acetylene with lithium in liquid ammonia followed, by the addition of anthraquinone leading to the monosubstituted propargyl alcohol 24. This synthesis can be mimicked by the addition of the commercially available suspension of sodium acetylide in xylenes to anthraquinone. These procedures, however, offer low yields of 24, and they are also unattractive because of difficult purification due to the low solubility of 24. In analogy to the pentacenequinone based synthesis of the monopropargyl alcohol the addition of trimethylsilyl (TMS) acetylene followed by the desilylation allows the high yield synthesis of ketone 24 (Scheme 43).[256, 272] In the first step of the reaction, a substoichiometric amount of n-BuLi is added to trimethylsilylacetylene in dry THF. In the following, step the lithium acetylide was added dropwise to an excess amount of anthraquinone (21) in THF to avoid the formation of the bis-adduct 9,10-bis((trimethylsilyl)ethynyl)-9,10-dihydroanthracene-9,10-diol (22). After aqueous workup, the unreacted anthraquinone can be removed via column chromatography on silica with CH2Cl2 as eluent yielding the ketone 23. The desymmetrization of anthraquinone via acetylide addition leads to the appearance of four aromatic signals in the 1H NMR spectrum of 23 at 8.17, 8.08, 7.71 and 7.51 ppm, with second-order coupling patterns characteristic of an ortho-substituted arene. Furthermore, singlets for the alcohol and TMS groups are observed at 3.16 and 0.16 ppm, respectively. The 13C NMR spectrum shows the moiety at 183.1 ppm and the three characteristic signals for a propargyl alcohol groups at 106.7, 91.5 and 66.4 ppm. The removal of the TMS group from 23 to give 24 leads to no change in the coupling pattern of the aryl protons in the 1H NMR spectrum, while the appearance of an additional signal corresponding to the alkyne proton at 2.71 ppm can be observed concurrent with the loss of the singlet of the TMS group. The solubility of 24 is
13 significantly decreased, however, and a C NMR spectrum can only be recorded in DMSO-d6 and shows the terminal alkyne carbon appearing at 76.1 ppm and the keto moiety at 182.4 ppm.
75 ! ! Results and Discussion ! !
TMS
O 1. n-BuLi / TMS-acetylene (< 1.0 eq.) OH 2. H2O THF
O O 21 23
KOH MeOH, H2O
TMS H
OH OH
HO O 24 TMS 22
Scheme 43. Synthesis of the TMS protected ketone 23, the deprotected propargyl alcohol 24 and the undesired bisadduct 22.
Similar to the method described for the fluorenyl based systems, the preparation of the corresponding ruthenium allenylidene complex (25A, 25B) was carried out by using an excess amount of propargyl alcohol 24 (Scheme 44). The formation of the intense purple color and the appearance of a peak at 1880 cm–1 in the IR spectrum, characteristic for allenylidene complexes, confirmed the successful conversion of the anthraquinone based. Separation of the two structural isomers was achieved following the procedure described above.
76 ! ! Results and Discussion ! !
Me Me N N O Me Me Me Me N O N N N N N Me Ru Me O O N O N N O N Ph3P Cl PPh3 14 Me Ru Me Me Ru Me C + THF Ph3P Cl + Ph3P C Cl H C C C C OH O
25A O 25B O
Scheme 44. Synthesis of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (AO = anthrone) (25A, 25B).
2 For the first isomer 25A the allenylidene carbon atoms Cα (292.1 ppm, d, JC,P = 26.8 Hz), Cβ 3 4 (251.0 ppm, d, JC,P = 5.0 Hz) and Cγ (141.4 ppm, d, JC,P = 3.0 Hz) appear as doublets in the 13 4 C NMR spectrum including long-range JC,P coupling between the triphenylphosphine ligand 31 and Cγ. A singlet is found in the P NMR spectrum at 30.1 ppm resulting from the triphenylphosphine ligand, which also supports the suggested structure. ESI-MS experiments again show the major observable signal resulting from the protonated monocationic species (m/z 863.14 (100%) MH+). For the structural isomer 25B with the allenylidene unit positioned
13 trans to the carboxylate, the C NMR spectrum shows a downfield shift for Cα (309.6 ppm, d, 2 JC,P = 19.8 Hz) and Cβ (277.0 ppm) relative to 25A. The third allenylidene carbon Cγ appears almost unchanged at 140.5 ppm, and a signal at 29.1 ppm in the 31P NMR spectrum confirms the triphenylphosphine ligand. The change in coordination geometry gives rise to an increase of 16 cm–1 (1896 cm–1) in the cumulene vibration compared to 25A. For the other ruthenium allenylidene complexes reported within this work, no clear trend for the allenylidene absorptions in the IR spectrum could be observed regarding A and B type isomers. However, in this case the difference might be explainable by a reduced linearity of the allenylidene moiety as described in the following part. ESI-MS experiments showed that the change in coordination in this complex strongly influence the stability of 25B although the monocationic complex can be observed the intensity is low (m/z 863.14 (4%) MH+). The major signals result from the dissociation of the chlorido ligand followed by decarboxylation
77 ! ! Results and Discussion ! c !
a b + of the bdmpza ligand (m/z 783.18 (88%) [M – Cl – CO2] ) and can be followed by addition of + one solvent molecule (m/z 824.21 (100%) [M – Cl – CO2 + MeCN] ).
C1 N22 N12
O2 C2
N11 N21 O1 Ru1
P1 Cl1 C31 C32 C33
C36
O3
Figure 25. Molecular structure of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and solvent molecules have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.138(3), Ru–N(21) = 2.193(3), Ru–O(1) = 2.077(2), Ru– P(1) = 2.3325(8), Ru–Cl(1) = 2.3761(8), Ru–C(31) = 1.868(3), C(31)–C(32) = 1.243(5), C(32)– C(33) = 1.362(5); N(11)–Ru–N(21) = 83.07(10), O(1)–Ru–N(11) = 87.20(9), O(1)–Ru–N(21) = 84.01(10), O(1)–Ru–P(1) = 83.87(6), P(1)–Ru–Cl(1) = 100.47(3), P(1)–Ru–C(31) = 86.76(10), O(1)–Ru– C(31) = 97.22(12), N(11)–Ru–P(1) = 170.16(8), N(21)–Ru–Cl(1) = 85.76(8), Cl(1)–Ru–C(31) = 92.65(10), Ru– C(31)–C(32) = 177.0(3), C(31)–C(32)–C(33) = 175.2(4).
The assignment of the relative geometry could be verified for both complexes from X-ray crystal structure analysis that were performed on crystals obtained from solutions in CH2Cl2 layered with n-hexane (Figure 25). Complex 25A (allenylidene trans to pyrazole) crystallizes as racemic mixture [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] × CH2Cl2 in space group P–1 with one solvent molecule disordered and parted over three positions. The distorted octahedral geometry is affected by the strained bdmpza ligand that shows values comparable to the fluorenyl allenylidene complex 20A discussed above. The change from the central 5- membered ring in the fluorenyl moiety to the 6-membered ring in the anthraquinone based
78 ! ! Results and Discussion ! ! system in complex 25A leads to increased steric repulsion between the anthrone moiety and the triphenylphosphine ligand. This results in a smaller bond angle ∠O(1)–Ru–P(1) (83.9°) compared to 92.7° in 20A and considerable greater angle ∠P(1)–Ru–Cl(1) (100.5°) in comparison to 92.1° (20A). The allenylidene unit itself shows rather unremarkable values of d(Ru–C(31)) = 1.868(3) Å, ∠Ru–C(31)–C(32) = 177.0(3)°, and ∠C(31)–C(32)– C(33) = 175.2(4)°.
a) b)
Figure 26. π–π stacking interactions between two molecules of 25A a) top view and b) side view.
Similar to complex 20A, π-π stacking interactions between two anthrone units are observed with approximately two thirds of the anthrone area affected resulting in a mean interplanar distance of 3.37 Å (Figure 26), as calculated between the least-squares plane generated from the carbon atoms of one anthrone moiety to the plane of its neighbor. For comparison, it is noted that anthraquinone shows a similar slipped stack arrangement in the solid state, with a mean interplanar distance of 3.48 Å.[273]
For the second structural isomer 25B (allenylidene trans to carboxylate) crystals of
[Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (Figure 27) in space group P–1 were obtained. Similar to the structures discussed above the positioning of the π donor and acceptor pyrazole trans to the chlorido ligand and the allenylidene trans to the carboxylate anchor leads to a loss of the trans-influence for both ligands. This change in the coordination sphere results in a shortened Ru–N(21) bond with 2.0740(18) Å and a similar Ru–C(61) bond with 1.862(2) Å. The bond angles of the allenylidene chain are with ∠Ru–C(61)–C(62) = 174.4(2)° and ∠C(31)–C(32)– C(33) = 169.8(3)° slightly reduced compared to 25A in contrast to the fluorenyl system (20A/20B).
79 ! a ! b Results and Discussion ! ! c
O2 C1 C2 N12 N22
O1 N21 N11
Ru1
C61 P1 Cl1 C62
C63
C67 O3
Figure 27. Molecular structure of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.1355(19), Ru–N(21) = 2.0740(18), Ru–O(1) = 2.1367(15), Ru–P(1) = 2.3546(6), Ru– Cl(1) = 2.4100(6), Ru–C(61) = 1.862(2), C(61)–C(62) = 1.232(3), C(62)–C(63) = 1.354(3); N(11)–Ru– N(21) = 83.87(7), O(1)–Ru–N(11) = 85.11(7), O(1)–Ru–N(21) = 86.94(7), O(1)–Ru–P(1) = 85.94(5), P(1)–Ru– Cl(1) = 87.68(2), P(1)–Ru–C(61) = 95.87(7), O(1)–Ru–C(61) = 178.13(8), N(11)–Ru–P(1) = 170.75(5), N(21)– Ru–Cl(1) = 174.12(5), Cl(1)–Ru–C(61) = 87.84(7), Ru–C(61)–C(62) = 174.4(2), C(61)–C(62)– C(63) = 169.8(3).
The explanation for this bent allenylidene unit can be deduced from the solid state packing motif of two neighboring complexes. The space filling model clarifies that only a small overlap of two anthrone units is observed due to the presence of one phenyl ring (dark grey) of the triphenylphosphine ligand on top of the anthrone moiety, which thus blocks the π-π interactions as observed for 25A and forcing the neighboring allenylidene chain into a slightly bent structure in the solid state (Figure 28).
80 ! ! Results and Discussion ! !
Figure 28. Space-filling model of complex 25B; phenyl ring highlighted in dark grey, anthrone moiety highlighted in light grey.
For the anthraquinone based allenylidene complexes [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A, 25B) the influence of the anthrone unit is clearly visible and the difference between both structural isomers is obvious (Chapter 8.2). Three reversible redox processes can be observed and can be attributed to the Ru(II)/Ru(III) couple (466 mV/641 mV), the allenylidene moiety (–1013 mV/–870 mV) and the anthrone moiety (–1479 mV/–1315 mV). Apparently, the facile reduction of the anthrone unit leads to a positive shift for all three redox processes and this effect is especially prominent in the B-type isomer with the allenylidene moiety trans to the pyrazole unit.
The UV/Vis absorption spectra of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A, 25B) recorded in CH2Cl2 show several intense absorptions (Figure 29). The strong absorptions below 400 nm can again be attributed to ligand centered π–π* transitions involving the bdmpza and PPh3 ligand. As mentioned previously the strong absorption at 578 nm (25A) or –1 –1 550 nm (25B) with molar extinction coefficients around 14000 L mol cm correspond to a metal-perturbed π-π* transition of the allenylidene moiety and are bathochromic shifted in comparison to 20A/B. Again weak transitions can be observed in the NIR region for both complexes with two signals at 1331 and 939 nm for 25B (Figure 30). For 25A one broad signal at 1131 nm can be detected. These transitions can be assigned to HOMO → LUMO and HOMO–1 → LUMO excitations, which are MLCT transitions (Table 8).
81 ! ! Results and Discussion ! !
30000
25000
] 20000 /1 )cm /1 15000 )[L)mol ε 10000
5000
0 400 600 800 1000 1200 1400 1600 Wavelength)[nm]
Figure 29. Absorption spectrum of 25A (black) and 25B (grey) in CH2Cl2.
200
150 * ] .1 (cm .1 100 ([L(mol ε
50
0 800 1000 1200 1400 1600
Wavelength([nm]
Figure 30. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 25A (black)
and 25B (grey); signal caused by CH2Cl2 is indicated by *.
82 ! ! Results and Discussion ! !
Observed values Calculated values
Compound Wavelength Absorption Wavelength Transition dipole Transition [nm] coefficient [nm] moment [debye] [M–1 cm–1]
25A 1131 184 997 0.85 HOMO ! LUMO 879 0.25 HOMO–1 ! LUMO
25B 1331 155 1204 0.68 HOMO ! LUMO 939 204 905 0.24 HOMO–1 ! LUMO
Table 8. Calculated and measured transitions for 25A and 25B in the NIR region.
For further understanding the absorption spectra TD-DFT calculations have again been performed by E. HÜBNER for complexes 25A and 25B, which explain the absorptions at the edge of the NIR region. Especially, the HOMO → LUMO and HOMO–1 → LUMO transitions with low transition dipole moments between 0.24 and 0.85 debye seem to correspond to forbidden MLCT transitions for both structural isomers (Table 8). The calculated geometries emphasize that the LUMO is delocalized over the ruthenium center as well as the entire allenylidene moiety and the anthrone unit for both complexes (Figure 31 and Figure 32). The B type isomer seems to show a stronger involvement of the anthrone unit to the calculated orbital in comparison to the A type complex. The HOMO and HOMO–1 are mainly located on the ruthenium center, Cα and Cβ for both isomers. The comparison of the calculated absorptions with the measured values (Table 8) confirm the assumption of the MLCT between the calculated orbitals.
83 ! ! Results and Discussion ! !
LUMO HOMO
HOMO–1 HOMO–2
Figure 31. Orbital diagrams of the LUMO (–3.2 eV), HOMO (–5.3 eV), HOMO–1 (–5.5 eV) and HOMO–2
(–5.7 eV) of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A).
84 ! ! Results and Discussion ! !
LUMO HOMO
HOMO–1 HOMO–2
Figure 32. Orbital diagrams of the LUMO (–3.2 eV), HOMO (–5.2 eV), HOMO–1 (–5.5 eV) and HOMO–2
(–5.8 eV) of [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25B).
85 ! ! Results and Discussion ! !
4.4.4 Pentacenequinone Based Allenylidene Complexes
Functionalized acenes have proven to be good candidates for small-molecule semiconductor applications and have been widely explored over the past decade.[274-276] In comparison to field-effect transistors (FETs) based on single-crystal, polycrystalline or amorphous silicon, those based on acene molecules allow the realization of large-area, mechanically flexible, and low-cost devices.[277] Likewise, the direct precursors to pentacenes, namely pentacene- quinones, are potentially useful organic semiconductors in their own right.[278] To date, the functionalization of the framework of pentacenes and pentacenequinones has focused on organic substituents and is accomplished mainly by appending alkyl, aryl, and alkyne residues to the framework to influence the HOMO–LUMO gap and packing motif in the crystalline state. [274-276, 279] The organometallic chemistry of pentacenes has been little explored,[280] and organometallic derivatives of pentacenequinone were unknown.
As a starting point for the pentacenone component, the known 13-hydroxy-13- [(triisopropylsilyl)ethynyl]pentacen-6-one (27)[272] was converted in cooperation with the group of R. TYKWINSKI into the propargyl alcohol 13-ethynyl-13-hydroxypentacen-6-one (28) by desilylation with TBAF (tetra-n-butylammonium fluoride) in THF (Scheme 45).[272]
TIPS H
I) II) O O HO O HO O
26 27 28
Scheme 45. Synthesis of the TIPS (triisopropylsilyl) protected alcohol 27 and deprotection of the propargyl
alcohol 28 (reaction conditions: I) 1. n-BuLi, TIPS-acetylene, THF, 2. H2O; II) TBAF, THF).
A similar approach as for the previously described complexes was used to obtain the corresponding heteroscorpionate allenylidene bdmpza complexes 29A and 29B. To the precursor [Ru(bdmpza)Cl(PPh3)2] (14), 1.5 equiv. of 13-ethynyl-13-hydroxypentacen-6-one
86 ! ! Results and Discussion ! !
(28) was added in THF. This led to the formation of a deep-blue solution after 4 d of stirring at room temperature (Scheme 46).
Me Me Me Me Me Me N N N N N N O O O N O N N O N + N O N Me Ru Me Me Ru Me Me Ru Me Cl Ph P Cl C Ph P C Cl Ph3P PPh3 3 C 3 C + C THF C O H O 29A 29B OH
O
28
Scheme 46. Synthesis of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (PCO = pentacenone) (29A, 29B).
As a result of the facial κ3 coordination of the bdmpza ligand the two expected structural isomers were formed, namely 29A and 29B. The neutral 18 VE allenylidene complexes 29A and 29B are rather stable towards oxygen and water. Therefore, the complexes were purified by column chromatography under aerobic conditions, although a clean separation of the two isomers was hindered in comparison to all previously describe bdmpza based allenylidene complexes.[61] However, it was possible to isolate trace amounts of the major isomer 29A from a mixture of 29A and 29B by column chromatography on silica gel
(CH2Cl2/acetone/n-hexane, 1:1:1, v/v/v). Surprisingly, all attempts to obtain pure 29B by chromatographic separation resulted in samples that contained traces of isomer 29A. Nevertheless, crystals suitable for an X-ray structure determination of 29B were obtained by slow diffusion of n-hexane into a solution of the complex 29B in CH2Cl2 (Figure 33).
87 ! ! Results and Discussion ! !
a b O2 c
C2 C1 O1 N22
Cl1 N21 N12 N11 P1 Ru1
C101
C102
C103
C106 O3
Figure 33. Molecular structure of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules dichloromethane have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.0881(16), Ru–N(21) = 2.1394(17), Ru– O(1) = 2.1458(14), Ru–P(1) = 2.3435(5), Ru–Cl(1) = 2.3884(5), Ru–C(101) = 1.861(2), C(101)– C(102) = 1.263(3), C(102)–C(103) = 1.363(3); N(11)–Ru–N(21) = 83.59(7), O(1)–Ru–N(11) = 85.01(6), O(1)– Ru–N(21) = 86.76(6), O(1)–Ru–P(1) = 86.23(4), P(1)–Ru–Cl(1) = 89.036(18), P(1)–Ru–C(101) = 97.39(6), O(1)–Ru–C(101) = 173.68(7), N(11)–Ru–P(1) = 99.60(5), N(21)–Ru–Cl(1) = 87.14(5), Cl(1)–Ru– C(101) = 95.20(6), Ru–C(101)–C(102) = 167.78(17), C(101)–C(102)–C(103) = 163.2(2).
The ruthenium complex 29B exhibits an octahedral geometry that is slightly distorted due to the facial coordinating N,N,O ligand with the allenylidene unit positioned trans to the
carboxylate and the PPh3 as well as the chlorido ligand trans to the pyrazole donors. In
comparison with other ruthenium allenylidene complexes, the Ru–C3 chain is extremely bent with angles ∠Ru–C(101)–C(102) = 167.78(17)° and ∠C(101)–C(102)–C(103) = 163.2(2)° (Table 9). These distorted angles might be caused by crystal packing effects and are unprecedented for mononuclear ruthenium allenylidene complexes.[281] The distortion of the sp carbon chain can be explained by strong π–π stacking interactions in the solid state that
88 ! ! Results and Discussion ! ! force the allenylidene unit into this bent structure. In the crystal structure, two pentacenone units are stacked with less than half a phenyl ring slippage and a mean interplanar distance of 3.63 Å (Figure 34).
Figure 34. π–π stacking interactions between two molecules of 29B from a) side view and b) top view.
This is in good agreement with the distance reported for 27 (3.60 Å), but is longer than in pentacenequinone (ca. 3.4 Å).[282-283] These favorable π-stacking interactions could lead to aggregation in solution, which would explain the difficult separation of the isomers by column chromatography. In addition, the pentacenone units are arranged parallel throughout the crystal lattice with a diagonal distance of around 3.9/4.0 Å between two neighboring pentacenone units, giving a structure resembling a staircase. TD-DFT calculations by E.
HÜBNER on a single molecule and neglecting π interactions led to an almost linear
89 ! ! Results and Discussion ! ! allenylidene moiety (Table 9). This supports the assumption that the considerable deviations in the solid state are a result of strong π–π stacking interactions. Cyclic voltammetric (CV) analysis of complex 29B revealed several ligand based and one ruthenium based redox transitions (see Chapter 8.2). The Ru(II)/Ru(III) couple is totally irreversible and appears at +0.92 V. A weak reversible oxidation is observed at +0.12 V and derives most likely from the pentacenone unit. Two reversible peaks at –0.48 and –0.88 V indicate facile reduction of the pentacenone and allenylidene moieties. The latter peak at –0.88 V agrees well with values of other ruthenium allenylidene complexes reported in the literature.[125] Further reversible reductions are observed at –1.40 and –1.83 V. In summary, these data seem to indicate that 29B has potential electron-acceptor properties.
The UV/Vis spectrum of 29B recorded in CH2Cl2 is depicted in Figure 35 and a magnification of the relevant parts of the NIR region is given in Figure 36. The strong absorption bands (55000 L mol–1 cm–1 for 29B) below 400 nm have been assigned to ligand-centered (LC) π–
π* transitions involving the PPh3 and bdmpza ligands. An additional metal-perturbed π–π* transition can be observed at 605 nm (ε ≈ 14000 L mol–1 cm–1), and the broad transitions at lower wavelengths (830–1400 nm) can be attributed to HOMO–1→LUMO and HOMO→LUMO excitations, which are MLCT transitions.
60000
50000 ] /1 40000 )cm /1
30000 )[L)mol ε 20000
10000
0 400 600 800 1000 1200 1400
Wavelength)[nm]
Figure 35. Absorption spectrum of 29B in CH2Cl2.
90 ! ! Results and Discussion ! !
400
350
300 * ]
.1 250 (cm .1 200
([L(mol 150 ε
100
50
0 900 1000 1100 1200 1300 1400 Wavelength([nm]
Figure 36. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 29B.
To further understand the UV/Vis data, DFT calculations were performed on 29B by E.
HÜBNER. TD-DFT calculations of the excited states revealed two absorption bands located at the edge of the NIR region (830–1400 nm, 370 L mol–1 cm–1). The two bands were assigned to metal-to-ligand charge-transfer transitions. The absorption band at lower wavelength for the first excited state was calculated to be at 1114 nm (i.e., 1.11 eV) and correlates mainly to a HOMO→LUMO transition. The second absorption band was calculated to be at 857 nm (i.e., 1.45 eV) and correlates to a HOMO–1→LUMO transition. Both occupied orbitals are mainly located on the ruthenium center in the d orbitals with some of the electron density extending towards the adjacent chlorido ligand as well as the oxygen atom of the carboxylate group of the bdmpza ligand. The lowest unoccupied orbital is delocalized mainly throughout the pentacenone ligand (Figure 37). The high degree of delocalization might explain the long- wave absorption bands because, as a consequence, the LUMO is expected to have a rather low energy, leading to a small energy difference between the occupied and unoccupied orbitals. For both transitions, the dipole moment was calculated to be rather small (0.65 and 0.17 debye), which indicates forbidden transitions. The HOMO→LUMO gap, calculated as the difference between the calculated orbital energies of the ground state (DFT) of 29B, is 2.0 eV, and this correlates reasonably well with the long-wavelength absorption bands found experimentally. The longest wavelength absorption bands obtained by the more accurate TD- 91 ! ! Results and Discussion ! !
DFT (1.1 to 1.4 eV), however, match the experimental CV data better, revealing a HOMO– LUMO gap of around 1.4 eV, which agrees as well as the UV/Vis data (0.9 to 1.5 eV).
LUMO HOMO
HOMO–1
Figure 37. Orbital diagrams of the HOMO–1 (–5.4 eV), HOMO (–5.1 eV), and LUMO (–3.06 eV) of
[Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29B).
92 ! ! Results and Discussion ! !
Experimental Calculated
Distances [Å] 29A 29B 29A 29B
Ru–Cα 1.859(3) 1.861(2) 1.868 1.875
Cα–Cβ 1.244(5) 1.263(3) 1.263 1.265
Cβ–Cγ 1.365(5) 1.363(3) 1.359 1.359
Angles [°]
Ru–Cα–Cβ 172.8(3) 167.78(17) 174.41 174.51
Cα–Cβ–Cγ 179.0(4) 163.2(2) 176.40 175.75
Table 9. Selected distances and angles for complexes 29A and 29B determined from the X-ray crystal structure and theoretical calculations (LACVP*/B3LYP).
The same TD-DFT calculations were performed for complex 29A. For the three calculated occupied orbitals HOMO–2, HOMO–1 and HOMO the orbitals are again mainly located on the ruthenium center in the d orbitals with some of the electron density extending towards the adjacent chlorido ligand as well as the oxygen atom of the carboxylate group of the bdmpza ligand (Figure 38).
The LUMO is delocalized mainly throughout the pentacenone ligand. However, the change in geometry from the allenylidene unit positioned trans to the carboxylate unit (29B) to trans to the pyrazole unit (29A) seems to reduce the delocalization of the HOMO within the pentacenone unit (Figure 38).
93 ! ! Results and Discussion ! !
LUMO HOMO
HOMO–1 HOMO–2
Figure 38. Orbital diagrams of the LUMO (–3.0 eV), HOMO (–5.2 eV), HOMO–1 (–5.3 eV) and HOMO–2
(–5.5 eV) of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A).
In comparison the second structural isomer (29A) shows the expected behavior for a bdmpza based allenylidene complex in crystalline state. The arrangement with the allenylidene unit positioned trans to a pyrazole unit forces the chlorido ligand trans to the carboxylate anchor. The allenylidene chain exhibits common angles with ∠Ru–C(61)–C(62) = 172.8(3)° and ∠C(61)–C(62)–C(63) = 179.0(4)°. This indicates that in the solid state less repulsion occurs, compared to complex 29B, thus, allowing the allenylidene moiety to maintain its preferred geometry.
94 c ! b ! Results and Discussion ! a !
C1 N12 N22 O2 N21 C2 N11 O1 Cl1 Ru1 C61 C62 P1 C63
C74 O3
Figure 39. Molecular structure of [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules dichloromethane have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.142(3), Ru–N(21) = 2.196(3), Ru–O(1) = 2.079(2), Ru–P(1) = 2.3325(10), Ru–Cl(1) = 2.3770(9), Ru–C(61) = 1.859(3), C(61)–C(62) = 1.244(5), C(62)– C(63) = 1.365(5); N(11)–Ru–N(21) = 83.03(10), O(1)–Ru–N(11) = 87.15(10), O(1)–Ru–N(21) = 83.38(10), O(1)–Ru–P(1) = 83.79(7), P(1)–Ru–Cl(1) = 99.43(3), P(1)–Ru–C(61) = 89.24(11), O(1)–Ru–C(61) = 95.41(13), N(11)–Ru–P(1) = 170.45(8), N(21)–Ru–Cl(1) = 88.72(7), Cl(1)–Ru–C(61) = 92.13(11), Ru–C(61)– C(62) = 172.8(3), C(61)–C(62)–C(63) = 179.0(4).
The packing motif in the solid state resembles for 29A more or less the packing motif of the anthraquinone based complex (25A) although due to the extended ring system only partial overlap of four phenyl rings can be observed (Figure 40). This can be attributed to the fifth phenyl ring being slightly forced out of the planar system due to repulsive interactions with the PPh3 ligand. For a possible application of pentacene or pentacenequinone based compounds in, for example, field effect transistors, efficient overlap of the planar π-systems is crucial in order to allow for charge transport along this axis.[274]
95 ! ! Results and Discussion ! ! a) b)
Figure 40. π–π stacking interactions between two molecules of 29A from a) top view and b) side view.
The arrangement observed for 29A and 29B in the crystalline state renders the complexes promising candidates for metal-tuned FETs or “organic” metal-semiconductor field-effect transistors (OMESFETs), whereas the electron-accepting ability and low-energy absorption characteristics might be tuned for use in solar cells. Both aspects present an appealing starting point for new kinds of functionalized organic semiconductors.
96 ! ! Results and Discussion ! !
4.4.5 Vinylidene Complex Bearing a Malonodinitrile Substituted Pentacenequinone
A common way to modulate the electron-accepting properties of quinones is the formation of the corresponding tetracyano-p-quinodimethane (In the case of unsubstituted quinone: 7,7,8,8-tetracyano-p-quinodimethane (TCNQ)) by reacting the quinone with malonodinitrile in the presence of titanium(IV) chloride.[284-285] Especially TCAQ (11,11,12,12-tetracyano- 9,10-anthraquinodimethane) has played an important role in the area of organic electron acceptors and its properties have been extensively reviewed.[286] The major drawback of most TCNQ based polyaromatic systems is the stabilization of the resulting radical anion resulting from the reduction of the electron acceptor. M. HANACK et al. synthesized a series of symmetrical acene based TCNQ derivatives like TCPQ (15,15,16,16-tetracyano-6,13- pentacenequinodimethane) that however, were poorer electron acceptors as indicated by the more negative reduction potentials observed in CV analysis.[285] Unsymmetrical acenes bearing acetylene moieties on one side and malonodinitrile units one the opposing side are currently a project investigated by A. WATERLOO in the group of R. TYKWINSKI. Starting from the previously used 13-ethynyl-13-hydroxypentacen-6-one (28), the reaction with malonodinitrile in the presence of TiCl4 leads to the isolation of 2-(13-(dicyanomethyl)-13- ethynylpentacen-6(13H)-ylidene)malononitrile (30) as the reaction with the hydroxyl moiety could not be avoided. In cooperation, it was decided to investigate the reaction of this acetylene derivative with the [Ru(bdmpza)Cl(PPh3)2] (14) precursor to explore the effects of the electron withdrawing groups. Reacting [Ru(bdmpza)Cl(PPh3)2] (14) with 30 in THF led within minutes to a dark blue solution very similar to 29A/29B, nevertheless the solution obtained is highly sensitive towards oxygen as it turns from blue to brownish green within hours (Scheme 47). From this lack of stability it was expected that the formed complex 31 might be the corresponding vinylidene complex (For the sake of simplicity the pentacene- quinone derivative of the vinylidene complex 31 is referred to as PCN).
97 ! ! Results and Discussion ! !
Me Me N N O Me Me N O N N N O Me Ru Me N O N Cl Ph3P PPh3 Me Ru Me + Ph P Cl C CN THF 3 CH H CN CN CN
NC CN 31 NC CN 30
Scheme 47. Synthesis of [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (PCN = pentacenone based tetracyano derivative) (31).
Due to the poor stability under aerobic conditions, the isolation of complex 31 via column chromatography was performed under nitrogen atmosphere with CH2Cl2/acetone (1:1, v/v, silica). It was concluded that compound 31 has the vinylidene moiety positioned trans to a pyrazole unit as no second structural isomer could be observed. In the 1H NMR spectrum the bdmpza ligand can be assigned by its characteristic four methyl signals at 2.51, 2.15, 1.94 and 1.91 ppm. One of the pyrazole protons in 4 position is shifted upfield to 4.98 ppm while the second one shows a more common value with 5.93 ppm. Furthermore, the vinylidene proton shows an extremely low value for an aromatic vinylidene complex of 3.82 ppm, which might result from the strong electron withdrawing groups of the substituent.[61] The aliphatic proton at 3.47 ppm and several aromatic protons between 8.68 and 7.65 ppm characterize the PCN moiety. Moreover, only one set of signals of the PCN moiety can be observed indicating free
13 rotation around the Cβ–Cγ bond. The C NMR spectrum confirms the aforementioned assumption that the vinylidene ligand is positioned trans to a pyrazole moiety as a long range P–C coupling can be observed for one 4 position pyrazole carbon atom at 106.6 ppm
4 [186] ( JC,P = 2.9 Hz). Additionally, the presence of Cα gives rise to a doublet downfield shifted 2 to 365.1 ppm ( JC,P = 39.1 Hz) clearly providing evidence for a vinylidene complex. Furthermore, a set of four signals of the cyano substituents at 119.1, 113.4, 110.6 and 110.1 ppm confirm the obtained complex 31. In addition the pentacenequinone backbone
98 ! ! Results and Discussion ! ! leads to several aromatic signals between 134.6 and 126.9 ppm. The 31P NMR spectrum supports the assumption that only one structural isomer has been formed as one strongly downfield shifted singlet at 44.6 ppm can be observed. The IR spectrum confirms the presence of two weak nitrile vibrations at 2198 and 2126 cm–1 arising from the two different sets of nitrile moieties. Finally ESI-MS experiments allowed the detection of the protonated complex 31 (m/z 1077.21 (15%) MH+) and its sodium adduct (m/z 1099.20 (100%) [M + Na]+).
The intense blue color of complex 31 seems to indicate an allenylidene complex, thus UV/Vis absorption spectroscopy was performed to compare the spectrum to the closely related ruthenium allenylidene complexes 29A and 29B based on pentacenequinone. The signals below 450 nm resemble the typical pattern for ruthenium bdmpza based complexes. However, a very broad absorption with maxima at 578 and 692 nm and high molar extinction coefficients between 6000 and 8000 L mol–1 cm–1 can be observed (Figure 41), although these extinction coefficients are high, in comparison to the allenylidene complexes reported previously, the values are moderate. A possible explanation would be that the electron withdrawing nitrile substituents lead to a strong bathochromic shift and the absorptions observed are similar to the allenylidene complexes metal-perturbed π–π* transitions, but in this case of the vinylidene unit. A further feature of 31 is an intense absorption in the NIR region between 1000 and 1087 nm with an molar extinction coefficient around 800 L mol–1 cm–1 that could not yet be attributed to a certain transition due to the lack of a single crystal X-ray structure determination and thereafter TD-DFT calculations (Figure 42). Nevertheless, a HOMO–LUMO transition seems logical in analogy to values reported in this work for the allenylidene complexes.
99 ! ! Results and Discussion ! !
35000
30000
25000 ] /1 20000 )cm /1
15000 )[L)mol ε 10000
5000
0 400 600 800 1000 1200 1400 1600 Wavelength)[nm]
Figure 41. Absorption spectrum of 31 in CH2Cl2.
1000
800 ]
-1 600 'cm
-1 *
400 '[L'mol ε
200
0 800 1000 1200 1400 1600 Wavelength'[nm]
Figure 42. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 31; signal
caused by CH2Cl2 is indicated by *.
100 ! ! Results and Discussion ! !
4.4.6 Benzotetraphenone Based Allenylidene Complexes
In the next step the focus was more on the packing motif in the solid state. For theoretical device formation a 3D electronic communication in the solid state is required. This can be achieved either by intramolecular transport within a polymer or intermolecular via close distance interactions by π-π stacking interactions.[272, 287] Based on the previous results, it was assumed that the allenylidene substituent is too close to the PPh3 and the bdmpza ligand to show extended intermolecular stacking interactions. Hence it was decided to look into related carbon-rich compounds that show substitution patterns extending the size of the polyaromatic system in the opposing direction to the allenylidene chain. For comparable size, 7H- benzo[no]tetraphen-7-one (10,11-BzBT, 34) consisting of five six-membered rings was chosen. Due to the so called 1,7 interaction the molecule is greatly distorted from a planar geometry, even in comparison to the closely related 7H-benzo[hi]chrysene-7-one (8,9-BzBT, 32) and 13H-dibenz[a,de]anthracen-13-one (5,6-BzBT, 33) (Figure 43).[288]
* *
* O O * O 32 33 34
Figure 43. 7H-benzo[hi]chrysene-7-one (8,9-BzBT, 32), 13H-dibenz[a,de]anthracen-13-one (5,6-BzBT, 33) and structures of 7H-benzo[no]tetraphen-7-one (10,11-BzBT, 34) (steric repulsion indicated with *).[288]
Starting from compound 34 is most promising as two of the phenyl rings are facing away from the keto moiety and in consequence from the future allenylidene unit. Thus it was decided to investigate the follow up chemistry of 10,11-BzBT as up to now only the nitration of the aromatic backbone, the dimerization of two units and the reduction of the keto moiety is know to literature.[289-291]
101 ! ! Results and Discussion ! !
TMS H
O OH OH
I) II)
34 35 36
Scheme 48. Synthesis of the TMS-ethynyl alcohol 35 and the deprotected propargyl alcohol 36 (reaction
conditions: I) 1. n-BuLi, TMS-acetylene, THF, 2. H2O; II) KOH, MeOH, H2O).
Starting from 7H-benzo[no]tetraphen-7-one (34) (Scheme 48), the addition of excess amounts of lithiated TMS-acetylene leads to the quantitative formation of the corresponding propargyl alcohol indicated by the characteristic singlets of the alcohol proton at 2.59 ppm and the TMS group at 0.23 ppm in the 1H NMR spectrum. In the 13C NMR spectrum of compound 35, the two relevant alkyne signals appear at 107.6 and 93.2 ppm, while that of the tetrahedral carbon is observed at 69.9 ppm. The product gives a signal in negative mode of ESI-MS analysis that can be attributed to a chloride adduct of 35 (m/z 413.11 (18%) [M + Cl]–). Deprotection of the alkyne is achieved in methanol with potassium hydroxide. 7-Ethynyl-7H-benzo[no]tetraphen- 7-ol (36) shows the additional signal of alkyne proton at 2.91 ppm in the 1H NMR spectrum, while the singlet of the TMS group is lost. In the 13C NMR spectrum, the loss of the methyl resonance from the TMS group and the shift of the terminal alkyne carbon to 76.4 ppm support the successful transformation from 35 to 36.
102 ! ! Results and Discussion ! !
Me Me Me Me Me Me N N N N N N O O O N O N N O N + N O N Me Ru Me Me Ru Me Me Ru Me Cl Ph P Cl C Ph P C Cl Ph3P PPh3 3 C 3 14 C C + THF C H 37A OH 37B
36
Scheme 49. Synthesis of [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A, 37B).
The preparation of the corresponding benzotetraphene (BT) based ruthenium allenylidene complexes 37A/37B was carried out by combinig equimolar amounts of propargyl alcohol 36 and [Ru(bdmpza)Cl(PPh3)2] (14) (Scheme 49). The reaction mixture turns to deep blue, similar to the reaction to give pentacenequinone based allenylidene complexes 29A/29B indicating in both cases a strong influence of the size of the aromatic group on the color of the allenylidene complex. The separation of the two structural isomers can be achieved by column chromatography as described for the anthraquinone based allenylidene complexes
13 25A/25B. For the major isomer 37A, Cα shows a characteristic signal in the C NMR 2 spectrum at 273.6 ppm with a coupling constant of JC,P = 19.2 Hz. For Cβ (221.1 ppm, d, 3 4 JC,P = 3.5 Hz) and Cγ (139.8 ppm, d, JC,P = 1.7 Hz) the signals are also shifted upfield in comparison to the fluorenone, anthraquinone and pentacenequinone based systems. The allenylidene stretch appears in the IR spectrum at 1903 cm–1. A singlet in the 31P NMR spectrum of 37A is found at 35.2 ppm for the PPh3 ligand, supporting assignment of the allenylidene trans to a pyrazole moiety. ESI-MS experiments confirm the formation of the complex through detection of the molecular ion (m/z 934.18 (100%) [M]+) and similar to 24B the decarboxylation followed by chloride dissociation can be observed (m/z 855.22 (23%)
+ [M – CO2 – Cl] ). For isomer 37B similar upfield shifted signals for Cα (289.5 ppm, d, 2 JC,P = 18.4 Hz), Cβ (237.2 ppm) and Cγ (138.0) can be observed. The IR spectrum reveals an –1 allenylidene stretch in a similar region at 1907 cm . The PPh3 ligand shows a singlet in
103 ! ! Results and Discussion ! !
31P NMR spectrum of 37B confirming the assignment that the allenylidene is positioned trans to the carboxylate anchor. These values are overall in good agreement with the previously observed NMR chemical shifts for type B isomers in comparison to type A isomers.[61] ESI-MS experiments again show the appearance of a signal that is characteristic for the
+ ionized complex (m/z 934.18 (100%) [M] ). Layering a solution of 37A in CH2Cl2 with n-hexane gave crystals of complex 37A suitable for a single crystal X-ray structure determination. The compound crystallizes as racemic mixture in the space group P–1 with two disordered molecules CH2Cl2 in the asymmetric unit. A graphical presentation of the compound is illustrated in Figure 44. As mentioned previously for type A isomers the typical strained coordination of the bdmpza ligand is observed and the allenylidene unit is coordinated trans to a pyrazole group, which leaves the PPh3 ligand trans to the second pyrazole and the chlorido ligand trans to the carboxylate anchor.
104 b a c ! ! Results and Discussion ! !
O2 N12 N22
O1 N11 N21 Ru C61 P1 C62 C74 Cl1 C63 C73 C75 C72 C71
Figure 44. Molecular structure of [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and two molecules dichloromethane have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.159(5), Ru–N(21) = 2.199(5), Ru–O(1) = 2.091(4), Ru–P(1) = 2.2936(17), Ru–Cl(1) = 2.3803(16), Ru–C(61) = 1.878(6), C(61)–C(62) = 1.239(8), C(62)– C(63) = 1.374(8); N(11)–Ru–N(21) = 85.5(2), O(1)–Ru–N(11) = 86.85(19), O(1)–Ru–N(21) = 85.14(19), O(1)– Ru–P(1) = 86.09(13), P(1)–Ru–Cl(1) = 95.91(6), P(1)–Ru–C(61) = 89.08(17), O(1)–Ru–C(61) = 95.5(2), N(11)–Ru–P(1) = 172.60(14), N(21)–Ru–Cl(1) = 89.08(15), Cl(1)–Ru–C(61) = 90.02(17), Ru–C(61)– C(62) = 174.1(5), C(61)–C(62)–C(63) = 176.0(6).
The main feature of the structure of 37A is the nearly linear allenylidene moiety with ∠Ru– C(61)–C(C62) = 174.1(5) and ∠C(61)–C(62)–C(63) = 176.0°(6). The benzotetraphene group is non-planar, due to hydrogen-hydrogen repulsion that forces the phenalene and naphthalene portions out of planarity. For rational description of the distortion between the two units the twisting angle around the pseudo bond C(72)–C(74) is defined. The torsion angle ∠C(75)– C(74)–C(72)–C(71) = 32.58° is similar to the angle observed for the parent ketone (33.4°).[288] Also the distance C(71)–C(75) = 3.006 Å for 37A is close to the precursor which shows a distance of 2.993 Å.[288] The combination of reduced planarity and of an extended π-system facing away from the ruthenium center allows the formation of a stepwise arrangement within the crystal lattice. While the pentacenequinone based systems did not show any extended stacking motifs, several π–π stacking interactions can be observed for complex 37A (Figure 45). The mean distance between two neighboring phenalene units accounts to 3.39 Å, which
105 ! ! Results and Discussion ! ! indicates attractive interactions. For comparison the interplanar distance in the parent 10,11- BzBT (34) has been reported with 3.582 Å for the face to face stacked ketone.[288] For the naphthalene unit three short contact interactions between 3.25 and 3.62 Å to the neighboring phenalene unit can be observed. This slip-stacked arrangement leads to a staircase type arrangement in the crystal that might allow charge transport between the polyaromatic systems. a) b)
Figure 45. π–π stacking interactions between two molecules of 37A from a) side view and b) top view.
For the second structural isomer 37B only a single crystal X-ray structure determination of poor quality could be obtained due to a strongly disordered crystal. Nevertheless, qualitative interpretation of the structure reveals that due to steric hindrance of the remaining ligands no π–π stacking interactions can be observed for this isomer.
The voltammograms of the benzotetraphene based allenylidene complexes
[Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A, 37B) show mainly similarities to the fluorene based allenylidene complexes 20A and 20B, although the potentials again show dependence on the structural isomer (Chapter 8.2). The reversible redox process involving the Ru(II) center appears at 87 mV (37A) or 118 mV (37B) indicating a more cathodic process due electron releasing properties of the benzotetraphene unit. The first redox process at negative voltage can best be described as quasi-reversible for the reduction involving the allenylidene moiety (–1228 mV (37A); –1168 mV (37B)) due to the lower peak current ratios. The second process for the reduction of the benzotetraphene unit itself (–1914 mV (37A); –1859 mV (37B)) is fully reversible.
106 ! ! Results and Discussion ! !
The UV/Vis spectra of the benzotetraphene based systems 37A/B recorded in CH2Cl2 share several common features for ruthenium allenylidene complexes as previously reported (Figure 46).[61, 125, 127, 256] The strong absorptions at wavelengths less than ~450 nm have been assigned to ligand centered (LC) π–π* transitions involving the PPh3 and bdmpza ligands. An additional metal perturbed π–π* transition can be observed at 654 nm for 37B with a molar extinction coefficient around 15000 L mol–1 cm–1. In comparison to the complex of type B a further increase in absorption energy can be observed for the complex bearing the allenylidene unit positioned trans to the pyrazole moiety (708 nm for 37A) with a comparable extinction coefficient. Again, absorption bands are observed in the NIR region (Figure 47), thus E. HÜBNER performed TD-DFT calculations of the excited states on the basis of crystal structures of 37A. The results of the calculations of the excited states revealed two absorption bands at 1058 nm (1.17 eV) and 905 nm (1.37 eV) that can be assigned to MLCTs which are in good agreement with the experimental values (1097 nm, 989 nm) (Table 10). The first absorption correlates mainly to the HOMO → LUMO transition with the second one assignable to the HOMO–1 → LUMO transition. The HOMO and HOMO–1 orbital may be described as ruthenium d orbitals with a small contribution of the chlorido ligand and the carboxylate anchor of the bdmpza ligand (Figure 48). For the HOMO orbital electron density can be observed to extend towards the allenylidene chain. For the LUMO a high degree of delocalization along the allenylidene unit into the phenalene moiety of the benzotetraphene unit can be observed. Overall, this results in a rather low energy LUMO leading to a small energy difference between the occupied and unoccupied orbitals and thus long-wave absorptions can be observed. The two small transition dipole moments that are calculated (1.54 and 0.51 debye) indicate forbidden transitions, which correlate well with the low absorption coefficients that were observed experimentally (764 and 708 L mol–1 cm–1). Furthermore, the HOMO–LUMO gap calculated as the difference between the calculated orbital energies of the ground state (DFT) of 37A correlates less with the experimental CV data (calcd.: 2.0 eV, observed 1.36 eV).
107 ! ! Results and Discussion ! !
30000
25000
20000 ] /1 )cm
/1 15000 )[L)mol
ε 10000
5000
0 400 600 800 1000 1200 1400 1600 Wavelength)[nm]
Figure 46. Absorption spectrum of 37A (black) and 37B (grey) in CH2Cl2.
800
600 ] .1 * (cm .1 400 ([L(mol ε
200
0 800 1000 1200 1400 1600 Wavelength([nm]
Figure 47. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for of 37A (black)
and 37B (grey); signal caused by CH2Cl2 is indicated by *.
108 ! ! Results and Discussion ! !
LUMO HOMO
HOMO–1 HOMO–2
Figure 48. Orbital diagrams of the LUMO (–2.9 eV), HOMO (–4.9 eV), HOMO–1 (–5.1 eV) and HOMO–2
(–5.3 eV) of [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A).
Observed values Calculated values
Compound Wavelength Absorption Wavelength Transition dipole Transition [nm] coefficient [nm] moment [debye] [M–1 cm–1]
37A 1097 764 1058 1.54 HOMO ! LUMO 989 708 905 0.51 HOMO–1 ! LUMO
Table 10. Calculated and measured transitions for 37A in the NIR region.
109 ! ! Results and Discussion ! !
4.4.7 Larger Quinoidal Polyaromatic Compounds
Based on the previous results even larger graphene like systems were considered as suitable precursors in which an extension of the substituent along the direction of the allenylidene chain would lead to 3D stacking patterns. Derived from anthraquinone and pentacenequinone, several dimerized and fused systems are viable (Figure 49), although no synthetic route for peripentacenequinone has been described, so far.[292]
O O
O O 38 39 O O
O O O 40 41
O
42
Figure 49. Structures of the acenequinones (bisanthracenquinone/bianthrone (38), bispentacenequinone (40)) and fused acenequinones (bisanthenequinone (39), „fused bispentacenequinone“ (41), peripentacenequinone (42)).[292]
110 ! ! Results and Discussion ! !
From the structures shown in Figure 49, bisanthenequinone is a promising candidate due to its planarity and its considerable larger π system compared to the previously used systems. The bisanthenequinone structure is the lead structure for many naturally occurring pigments like hypericin controlling biophysical processes like phototoxicity and antiseptic actions.[293-294]
The first synthesis of 39 was described by R. SCHOLL in 1910 via oxidation of meso- benzdianthrone with potassium dichromate in concentrated sulfuric acid.[295] Given the recent interest in carbon-rich chemistry several groups have used bisanthenequinone based systems.
H. BOCK et al. used this as building block to create soluble and liquid-crystalline ovalenes,[296] which are of great interest for devices like field effect transistors and solar cells.[297-302] Closely related are dicyano ovalene diimides reported by J. WU et al. that allow solution processing of OFET devices, which show high electron mobility under aerobic conditions.[303] Further compounds by J. WU et al. focused on the reactivity of the meso positions and allowed the formation of NIR dyes that undergo several reversible redox processes.[304] Similar results were obtained for the parent bisanthene core that without meso-substituents rapidly decomposes.[305]
Based on these promising results it was decided to focus on the synthesis of an allenylidene complex bearing a bisanthenequinone unit. Starting from commercially available bianthrone
(38) required as first step a photocyclization reaction previously described by S. ARABEI and coworker.[306] Illumination was performed with a mercury vapor lamp and a solution of 38 in benzene, which reacted via intermediary helianthrone (43) in one step cleanly to bisanthenequinone (39, Scheme 50). Experiments showed that the cyclization can either be performed under an argon atmosphere or without inert gas, although the yields are higher in the presence of oxygen. The presence of oxygen leads to an orange product in comparison to a brownish product after inert gas conditions, although the spectroscopic datas are equivalent.
111 ! ! Results and Discussion ! !
O O O
hν hν
O O O 38 43 39
Scheme 50. Photocyclization reaction for the synthesis of bisanthenequinone (39).[306]
The poor solubility of bisanthenequinone (39) leads to precipitation from benzene and after removal of unconverted bianthrone the IR spectrum shows a shift for the two characteristic quinone signals. For 38 these two signals appear at 1667 and 1594 cm–1 and are shifted for 39 to lower wavenumbers at 1659 and 1582 cm–1. For further characterization, it was decided to measure a 1H NMR spectrum in deuterated concentrated sulfuric acid as no other solvent allows dissolution of 39. The signals confirm the high symmetry of the bisanthenequinone unit as only three signals can be observed. Two well resolved doublets at 8.63 and 8.22 ppm and a further signal that appears as triplet at 7.26 ppm are in agreement with the reported structure.
In the following step, the conversion of the quinone moiety into a propargyl alcohol by nucleophilic addition of acetylene precursors was attempted. As promising candidates sodium acetylide, ethynylmagnesium bromide and lithiated trimethylsilyl acetylide were added in equimolar amounts to 39 to form the monoaddition product (Scheme 51) in analogy to the anthraquinone and pentacenequinone systems.
112 ! ! Results and Discussion ! !
R
O OH
1. R R´ 2. H2O
R = H, R´ = Na O R = H, R´ = MgBr O R = TMS, R´ = Li 39 44
Scheme 51. Attempted syntheses of a bisanthenone propargyl alcohol (44).
Nevertheless, all described attempts failed to produce a propargyl alcohol. Due to the poor solubility of the resulting compounds, a positive identification of the obtained compounds is questionable. In comparison to the literature known bisanthenequinone derivatives that bear bulky or electron withdrawing groups on the reactive zigzag edges 44 lacks stabilization.[307] This might cause decomposition of 44 after formation. Another explanation might be a report by J. WU et al. indicating that lithiated species can be added to the bisanthenequinone backbone and not directly to the quinone moiety allowing the formation of a mixture of substances.[304] Based on these results, two routes seem promising. On the one hand, the symmetrical functionalization, known in literature to obtain 7,14-bis(triisopropylsilylethynyl)- phenanthro[1,10,9,8-opqra]perylene and after deprotection the formation of bimetallic allenylidene complexes.[305] On the other hand functionalization of the armchair area of the bisanthenequinone unit, which shows diene character, might be an opportunity.[303] Diels- Alder reaction with 1,4-naphthaquinone can introduce quinoidal systems that in a next step could be converted into a suitable precursor with strongly enhanced solubility in comparison to the unsubstituted bisanthenequinone system (Scheme 52).[308]
113 ! ! Results and Discussion ! !
tBu tBu tBu tBu
O O
Δ + benzene
O O
t t t t Bu Bu Bu Bu
Scheme 52. Functionalization of the bay region of soluble bisanthene derivatives by J. WU et al.[308]
114 ! ! Results and Discussion ! !
4.4.8 Carbon-Rich Allenylidene Complexes Based on [RuCl2(PPh3)3]
It has been reported previously that [RuCl2(PPh3)3] is a versatile starting compound for quite [93] stable 16 VE ruthenium allenylidene complexes like [RuCl2(═C═C═CPh2)(PPh3)2]. This complexes can be further stabilized as 18 VE complexes via coordination of solvents to form
[96] systems such as [RuCl2(═C═C═CPh2)(PPh3)2(solvent)] (solvent = H2O, MeOH, EtOH). A controlled dimerization to less reactive 18 VE bimetallic allenylidene complexes [(Ph3P)4(μ- [309] Cl)3Ru2(═C═C═CAr2)2]PF6 has been reported. Therefore, the corresponding fluorenone based allenylidene complex [RuCl2(═C═C═(FN))(PPh3)2] (45) was targeted by applying the conditions for the analogous diphenyl allenylidene complex. Heating [RuCl2(PPh3)3] with 9-ethynylfluoren-9-ol in THF for 2 h under reflux led to the formation of a deep red solution (Scheme 53). H
Ph3P Cl OH Δ [RuCl2(PPh3)3] + Ru C C C THF Cl PPh3
45
Scheme 53. Synthesis of [RuCl2(═C═C═(FN))(PPh3)2] (45).
The progress of the reaction could be monitored via IR spectroscopy by the disappearance of the alkyne peak and appearance of the resulting allenylidene peak at 1922 cm–1. After recrystallization from CH2Cl2/n-hexane, the compound was further characterized via its 13 characteristic C NMR spectrum showing the Cα at 313.8 and Cβ at 239.1 ppm. Both signals are shifted downfield in comparison to the analogous diphenyl allenylidene complex. The high symmetry of complex 45 leads to only one singlet for two triphenylphosphine ligands in the 31P NMR spectrum at 29.1 ppm. ESI-MS experiments verified the proposed structure as a monocationic species (m/z 849.12 (100%), [M – Cl]+) that fits complex 45 after loss of one chlorido ligand. The compound is easily obtained and long storage under anaerobic conditions is possible. Solutions of 45 in chlorinated solvents like CHCl3 and CH2Cl2 tend to form dimeric complexes as indicated by the formation of four doublets in 31P NMR spectrum. It is literature known that, if no strongly coordinating solvents like alcohols or pyridine are present the stabilization of the 16 VE complex can occur via dimerization processes.[93] For the
115 ! ! Results and Discussion ! !
[RuCl2(PPh3)3] based complexes two different structures are possible with one cationic (45A) and one neutral 18 VE complex (45B) (Scheme 54). In accordance to the previously reported
2 2 dimers the two doublets at 47.8 (d, JP,P = 35.6 Hz) and 47.1 ppm (d, JP,P = 37.3 Hz) can be assigned to the neutral allenylidene complex that consists of two µ2 bridged chlorido ligands and two terminal chlorido ligands with the allenylidene units positioned trans to each other.
2 In consequence the two remaining doublets at 37.3 (d, JP,P = 26.7 Hz) and 34.8 ppm (d, 2 JP,P = 26.7 Hz) are caused by the cationic form that contains a Ru2Cl3-cluster as a central feature with two ruthenium(II) centers bridged by three chlorido ligands resulting in a monocationic complex. The positive charge is compensated by a chloride counter anion that has been displaced from the monomeric ruthenium allenylidene complex.
Cl PPh3 C C C Ru Cl PPh3 Ph3P Cl Ru C C C
Ph3P Cl 45A
Cl
Ph3P PPh3 C C C Ru Cl Cl Cl Ru C C C
Ph3P PPh3
45B
Scheme 54. Dimerized neutral ruthenium allenylidene complex 45A and mono cationic allenylidene complex 45B.
For comparison of the ligand influence on the stability of the 16 VE complex the anthraquinone based precursor 10-ethynyl-10-hydroxyanthracen-9-one (23) was applied to form the corresponding complex based on [RuCl2(PPh3)3] ([RuCl2(═C═C═(AO))(PPh3)2] (46)) in analogy to the synthesis described above for 45. The complex 46 was obtained as a purple powder due to the influence of the enlarged aromatic system (Scheme 55).
116 ! ! Results and Discussion ! !
H
OH Ph3P Cl Δ [RuCl2(PPh3)3] + Ru C C C O THF Cl PPh3 O 23 46
Scheme 55. Synthesis of [RuCl2(═C═C═(AO))(PPh3)2] (46).
The characteristic Cα (321.0 ppm) and Cβ (271.9 ppm) appear downfield shifted compared to the analogous diphenyl ([RuCl2(═C═C═CPh2)(PPh3)2]) and fluorenyl ([RuCl2(═C═C═(FN))- [93] (PPh3)2] (45)) substituted allenylidene complexes. This indicates the ability of the enlarged aromatic system and the keto moiety to withdraw electron density from the allenylidene chain. The IR signal of the allenylidene is shifted towards lower wavenumbers and appears at 1904 cm–1. The monomeric structure could be confirmed by the 31P NMR spectrum showing a singlet at 25.1 ppm, characteristic for a symmetrical trans arrangement of the two PPh3 ligands. Similar to the fluorenyl based system the formation of two different dimers can be observed in 31P NMR spectroscopy experiments and the assignment is in agreement with the
[93] detailed reports by A. HILL et al regarding ([RuCl2(═C═C═CPh2)(PPh3)2]. For the neutral 2 2 dimer 46A signals at 48.3 (d, JP,P = 35.6 Hz) and 46.8 ppm (d, JP,P = 37.9 Hz) can be 2 observed. The cationic system 46B gives rise to two doublets at 36.3 (d, JP,P = 26.7 Hz) and 2 33.2 ppm (d, JP,P = 26.7 Hz). Finally, following again the procedure of Selegue, the pentacenequinone based propargyl alcohol 28 was combined with [RuCl2(PPh3)3] in THF under reflux, which led to the formation! of a deep-blue solution. Removal of the solvent and several cycles of recrystallization from CH2Cl2/n-pentane gave! the coordinatively unsaturated 16 valence electron complex 47 (Scheme 56).
117 ! ! Results and Discussion ! !
Ph P Cl HO 3 Δ [RuCl2(PPh3)3] + H O Ru C C C O THF Cl PPh3 28 47
Scheme 56. Synthesis of [RuCl2(═C═C═(PCO))(PPh3)2] (47).
As discussed above for [RuCl2(═C═C═(FN))(PPh3)2] (45) and [RuCl2(═C═C═(AO))(PPh3)2] (46), the dimerization of the resulting 16 VE allenylidene complex 47 occurs, depending on the temperature and solvent. After purification by several cycles of recrystallization, two AB quartet patterns can again be observed in the 31P NMR spectrum, which can be assigned to the two different dimer structures (Scheme 57). Based on spectroscopic analysis, one of the dimers contains two bridging and two terminal chlorido ligands, leading to a neutral 18 VE complex (47A). The second dimer, on the other hand, is the monocationic complex that contains three bridging chlorido ligands (47B). The positive charge is again compensated by a chloride anion that is released during dimerization.
Cl
Ph3P PPh3 Cl PPh3 (PCO) C C Ru Cl (PCO) C C Ru Cl PPh3 Cl Ph3P Cl Ru C C (PCO) Cl Ru C C (PCO) Ph3P Cl Ph3P PPh3 47A 47B
Scheme 57. Dimerized neutral ruthenium allenylidene complex 47A and mono cationic allenylidene complex 47B.
118 ! ! Results and Discussion ! !
4.5 Ruthenium Heteroscorpionate Cumulenylidene Complexes as Molecular Slides
Carbon nanotubes (CNTs)[310-312] are a key material in the nanotechnological progress[313] due to their physical properties (electrical, optical, mechanical, etc.) and their nanometer scale size.[314] The potential applications are ranging from electronics,[315] sensing[316] and energy conversion[317-321] to biological functions.[322] The first discovered CNTs were multiwalled carbon nanotubes (MWCNTs) consisting of several layers of tubes.[323] However, the leading nanotubular structures in terms of possible applications are singlewalled carbon nanotubes (SWCNTs), which can be described as small graphene like sheets that have been rolled up to cylinders.[314] However, strong intermolecular bundling in SWCNTs leads to difficulties in exfoliation of single strands and dispersing them afterwards in solution, especially in aqueous media. The common ways are the covalent functionalization, i.e. functionalization of the open edges or sidewall and the noncovalent interactions of aromatic molecules or macromolecules with the sidewall. The advantage of noncovalent functionalization is the preservation of the pristine sp2 hybrid state and the inherent electron transport properties.[324]
A wide variety of metallophthalocyanines and their CNT donor-acceptor systems are known to literature and have been extensively reviewed.[314] Only few metal complex based systems focusing on classical complex chemistry are known.[325-326] A first example was reported from
S. WONG and coworker, who described the addition of Wilkinson´s catalyst to oxidized CNTs.[327] On the one hand, this increased the solubility in a variety of organic solvents and exfoliation of larger nanotube bundles. On the other hand, the CNT worked as reusable catalyst support for homogenous hydrogenation of cyclohexene, demonstrating the conserved activity of the catalyst.[327] To name an example for the phthalocyanine based systems a pyrene conjugate by D. GULDI et al. can be named.[328] The pyrene anchor allows the noncovalent functionalization of CNTs and spectroscopic and photoelectrochemical techniques were used to characterize the resulting adducts. Integration into photoactive electrodes allowed the detection of stable and reproducible photocurrents.[328] A further interesting approach is the reversible solubilization performed by A. IKEDA et al. based on a
2+ [329] [Cu(bpy-R2)2] derivative bearing two cholesteryl groups. The square planar copper(II) complex allows π-π stacking interactions with the CNTs and leads to solutions of the aggregated compound. Upon reduction with ascorbic acid, the coordination geometry of the
119 ! ! Results and Discussion ! ! copper(I) center changes to tetrahedral and leads to precipitation of the CNTs. Reoxidation with oxygen leads to the former geometry and again a stable solution is formed. This behavior was tested in several cycles and allows the purification of metallic and semiconducting CNTs via modulation of the redox state of the copper center.[329]
Recently, A. MARTI et al. reported a series of cationic ruthenium(II) bpy complexes that are able to solubilize CNTs in aqueous media via noncovalent interactions.[330] The complexes
1 2+ 2 2+ 3 4+ [Ru(bpy)2L ] , [Ru(bpy)2L ] and [Ru(bpy)2L Ru(bpy)2] allow π-π stacking interactions with the CNTs and allow high individualization in water (Figure 50).
N N N N N N N
N N N N N N N
1 2 3 L L L
Figure 50. Ligands L1 (dppz = dipyrido[3,2-a:2´.3´-c]-phenazine), L2 (dppn = benzo[i]dipyrido-[3,2-a:2´.3´- c]phenazine) and L3 (tpphz = tetrapyrido[3,2-a:2´.3´-c:3´´,2´-h:2´´´,3´´´-j]phenazine) used by A. MARTI et al.[330]
4.5.1 Polyaromatic Ruthenium Vinylidene Complexes
Given the interest of the BURZLAFF group in carbon-rich cumulenylidene ruthenium complexes it was decided to synthesize a series of complexes that could be suitable for noncovalent functionalization of carbon nanotubes. Due to the simplicity of synthesis the first focus was on ruthenium vinylidene complexes bearing the bdmpza ligand. From previous work it was known that for acetylene compounds with small substituents a mixture of A and B type isomers is formed (see Scheme 28). Due to the sensibility of vinylidene complexes towards oxygen the separation was avoided, as column chromatography was not favorable. Thus two important questions are, if larger polyaromatic substituents stabilize the vinylidene complexes and if the steric demand leads to selective formation of A type isomers.
With the phenylacetylene based vinylidene complex already known to literature the next larger 2-ethynyl-6-methoxynaphthalene was picked as suitable precursor. Reaction of excess amounts of the ethynyl substituted naphthalene with [Ru(bdmpza)Cl(PPh3)2] (14) in THF at
120 ! ! Results and Discussion ! ! room temperature afforded an orange solution. Reducing of the solvent and cooling in the freezer led to crystallization of the complex [Ru(bdmpza)Cl(═C═CH(6-methoxy- naphthalene))(PPh3)] (48) (Scheme 58).
Me Me N N O N O N Me Me Me Ru Me N N O N O N Ph3P Cl PPh3 + Me Ru Me THF O H Ph P Cl C 3 C Me H
Me 48 O
Scheme 58. Synthesis of the vinylidene complex [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48).
The 1H and 13C NMR spectrum exhibit only one set of signals characteristic for an A type isomer indicating the influence of the steric demand of the substituent on the coordination
1 pattern. The H NMR spectrum of 48 shows the characteristic Hß, gained by the 1,2-H shift, at 4 5.11 ppm with a JH,P coupling constant of 4.7 Hz due to the PPh3 ligand. Furthermore, the four methyl groups of the bdmpza ligands appear at 1.87, 2.39, 2.46 and 2.53 ppm and the methoxy group at 3.88 ppm. The complete absence of further signals in the aliphatic region
13 proves the clean formation of one isomer. In the C NMR spectrum, the Cα signal is found at 2 363.2 ppm as a doublet with the coupling constant JC,P = 24.8 Hz and the Cß signal appears at 3 109.0 ppm as a doublet with the coupling constant JC,P = 3.0 Hz. The singlet at 37.3 ppm in the 31P NMR spectrum confirms the assignment to an A type isomer in comparison to the literature value of 37.5 ppm for the A type isomer of the complex [Ru(bdmpza)Cl-
[61] (═C═CHPh)(PPh3)] (B type: 32.3 ppm). The absence of vibrations between 2200 and 1800 cm–1 in the IR spectrum that would indicate alkyne moieties and the detection of the potassium adduct of complex 48 (m/z 867.12 (100%) [M + K]+) in ESI-MS experiments confirm the structure.
Based on this promising result, it was decided to synthesize a pyrene (Pyr) based vinylidene complex for possible applications as noncovalent linker to CNTs. Pyrene derivatives linked via a variety of spacer groups are widely spread in literature for CNT exfoliation and further applications.[331-342] In organometallic chemistry one example of pyrene substituted complexes
121 ! ! Results and Discussion ! ! is reported by R. WINTER et al., demonstrating the non-innocent behavior of a ruthenium vinylpyrenyl complex [(Pyr)CH═CH)Ru(CO)Cl(PPh3)3] allowing the large π ligand to heavily participate in electron-transfer processes.[343] The first example of a pyrene based
1 2 vinylidene complex [Ru(κ -OAc)(κ -OAc)(═C═CH(Pyr))(PPh3)2] has been reported by J. LYNAM et al. in 2012 in a study that emphasized the similar donor/acceptor properties of vinylidene and isocyanide ligands.[344]
The synthesis of the corresponding bdmpza based ruthenium complex was achieved similar to
48. [Ru(bdmpza)Cl(PPh3)2] (14) and 2.2 equivalents of 1-ethynylpyrene were stirred in THF at room temperature and after reducing the solvent and storing in the freezer the crystalline complex [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) was obtained (Scheme 59).
Me Me N N O N O N Me Me Me Ru Me N N O N O N Ph3P Cl PPh3 + Me Ru Me THF H Ph P Cl C 3 C H 49
Scheme 59. Synthesis of the vinylidene complex [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49).
Again only one set of signals characteristic for an A type isomer could be observed. The
1 H NMR spectrum indicates that the larger pyrene substituent leads to a deshielding of Hß and 4 thus to an increased chemical shift with 5.78 ppm and a coupling constant of JH,P = 4.7 Hz. The larger polyaromatic substituent shows less influence on the bdmpza ligand as the four methyl substituents of 49 appear with 1.88, 2.39, 2.49 and 2.55 ppm in a similar region
13 compared to 48. In the C NMR spectrum, Cα and Cß give rise to doublets at 359.1 2 3 ( JC,P = 23.1 Hz) at 111.8 ppm ( JC,P = 2.6 Hz). The deshielding influence apparently only influences Cß significantly as the Cα position appears further upfield shifted. In addition all 16 carbon atoms of the pyrene unit could be detected and the C–H multiplicities were assigned
122 ! ! Results and Discussion ! !
via APT 13C NMR experiments. Further prove for the molecular structure is provided by the singlet at 37.1 ppm in the 31P NMR spectrum and the detection of the molecular ion in ESI- MS experiments (m/z 872.16 (100%) M+).
Finally, the geometry of complex 49 could be unambiguously characterized by a single crystal X-ray structure determination. Crystals suitable for analysis were obtained from a
concentrated solution in CH2Cl2 layered with n-pentane stored in a Schlenk flask under argon atmosphere with a septum allowing slow evaporation. The complex crystallizes as racemic
mixture in space group P–1 with one molecule CH2Cl2 and a strongly disordered molecule n- pentane in the asymmetric unit (Figure 51).
b a c
N12 N22
O2 N21 O1 N11
Ru
Cl C71 P H72 C72
C73
Figure 51. Molecular structure of [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms (except the vinylidene proton) and solvent molecules have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.162(5), Ru–N(21) = 2.216(10), Ru–O(1) = 2.091(4), Ru–P = 2.322(4), Ru–Cl = 2.388(4), Ru–C(71) = 1.781(9), C(71)–C(72) = 1.315(10), C(72)–C(73) = 1.482(8); N(11)–Ru–N(21) = 81.3(2), O(1)–Ru–N(11) = 86.8(2), O(1)–Ru–N(21) = 83.7(2), O(1)–Ru–P = 87.05(17), P–Ru–Cl = 96.16(14), P–Ru–C(71) = 87.5(2), O(1)–Ru–C(71) = 97.5(3), N(11)–Ru– P = 173.61(13), N(21)–Ru–Cl = 86.2(2), Cl–Ru–C(71) = 92.3(2), Ru–C(71)–C(72) = 173.7(5), C(71)–C(72)– C(73) = 123.8(6).
Complex 49 shows the typical strained octahedral coordination of the bdmpza ligand with the vinylidene ligand positioned trans to one pyrazole moiety. The angles and distances for the
123 ! ! Results and Discussion ! ! bdmpza ligand are in good agreement with the previously reported bdmpza based vinylidene
[61] complex [Ru(bdmpza)Cl(═C═CH(Tol))(PPh3)] (Tol = tolyl). The vinylidene moiety exhibits an angle ∠Ru–C(71)–C(72) = 173.7(5)° with bond lengths dRu–C(71) = 1.781(9) Å and dC(71)–C(72) = 1.315(10) Å that are similar to the tolyl complex and the pyrene based
1 2 [61, 344] vinylidene complex [Ru(κ -OAc)(κ -OAc)(═C═CH(Pyr)(PPh3)2] (Table 11).
Complex Ru–Cα / [Å] Cα–Cß / [Å] ∠Ru–Cα–Cß / [°]
[Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] 1.781(9) 1.315(10) 173.7(5) (49)
[Ru(bdmpza)Cl(═C═CH(Tol))(PPh3)] 1.821(13) 1.347(18) 176.7(11)
[Ru(κ1-OAc)(κ2-OAc)(═C═CH(Pyr))- 1.7863(16) 1.325(2) 174.72(14)
(PPh3)2]
Table 11. Overview of characteristic bond lengths and angles of ruthenium vinylidene complexes 1 2 [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49), [Ru(bdmpza)Cl(═C═CH(Tol))(PPh3)] and [Ru(κ -OAc)(κ -OAc)- [61, 344] (═C═CH(Pyr))(PPh3)2].
The torsion angle ∠C(61)–C(62)–C(63)–C(64) is a good indicator for possible conjugation between the metal center and the pyrenyl unit. Complex 49 shows an angle of approximately 36°. This is quite large in comparison to the tolyl based complex [Ru(bdmpza)Cl-
(═C═CH(Tol))(PPh3)], which has a torsion angle of –18°. The rotation around the C(62)– C(63) axis should not be hindered and in solution a planar arrangement might be achievable.
124 ! ! Results and Discussion ! !
30000
25000
20000 ] /1 )cm
/1 15000
)[L)mol 10000 ε
5000
0 400 600 800 1000 1200 1400 1600
Wavelength)[nm]
Figure 52. Absorption spectrum of 49 in CH2Cl2.
250
200 ]
.1 150 (cm .1
100 ([L(mol ε
50
0 800 1000 1200 1400 1600 Wavelength([nm]
Figure 53. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for 49; signal
caused by CH2Cl2 is indicated by *.
125 ! ! Results and Discussion ! !
The absorption spectrum of complex 49 measured in CH2Cl2 shows the expected pattern for a ruthenium vinylidene complex based on bdmpza (Figure 52). Two intense absorptions at 406 and 389 nm with high molar extinction coefficients (~21000 L mol–1 cm–1) can be attributed to a metal-perturbed π–π* transition of the vinylidene moiety and ligand centered π–π* transitions of the bdmpza and PPh3 ligand. In addition, a further weak absorption can be observed in the NIR region at 921 nm (~200 L mol–1 cm–1) as reported for the vinylidene complex [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31) (Figure 53).
Complexes 48 and 49 are remarkably stable in the presence of oxygen. This is noteworthy since for possible applications like exfoliation and non-covalent functionalization of CNTs, higher stability is required to simplify procedures.
126 ! ! Results and Discussion ! !
4.5.2 Pyrene Based Allenylidene Complexes
As described in the previous chapters, ruthenium allenylidene complexes have proven to be good candidates for remarkably stable organometallic compounds. A common disadvantage is however, that the Cγ position needs to be stabilized with aryl substituents as protons or alkyl substituents might lead to decomposition or rearrangement into vinylvinylidene complexes.[157] Hence, pyrenophenone (50) was picked as conveniently available compound, as it can be easily obtained by a Friedel-Crafts Acylation of pyrene with benzoyl chloride (Scheme 60).[345-346] This compound has recently been employed as starting material for several ethenes showing aggregation-enhanced excimer emission and electroluminescence.[346] Furthermore, it is reported that 50 can undergo a Scholl Reaction creating an additional five- or six-membered ring (Scheme 60, compound 52), depending on the publication.[291, 345, 347] Therefore, it was decided to a) synthesize from pyrenophenone (50) the corresponding propargyl alcohol 51 and convert the alcohol into the bdmpza based allenylidene complex and b) explore the Scholl reaction and if possible synthesize a second propargyl alcohol 53 with extended π system.
127 ! ! Results and Discussion ! !
O O O
or
52 50
H H
OH OH OH H or
51 53
Scheme 60. Synthetic overview of propargyl alcohols 53 and 51 that should be available starting from pyrenophenone (50).[291, 345, 347]
Pyrenophenone (50) was synthesized according to literature via a Friedel-Crafts Acylation of pyrene.[346] Since the synthesis of the compounds 52 and 53 was not as straight forward as expected these compounds will be discussed in detail in chapter 4.6.
Crystals of pyrenophenone (50) suitable for a single crystal X-ray structure determination could be obtained from slow evaporation of a solution of 50 in a mixture of CH2Cl2 and n- hexane. The ketone crystallizes in space group P–1 and confirms the previously reported connectivity of the pyrenyl residue (Figure 54). The keto moiety shows a bond length dC(1)– O(1) = 1.2227(15) Å and the three surrounding angles are close to 120°, which is in good agreement with free rotation around the single bonds.
128 ! ! Results and Discussion ! !
C13 C11 C14 O1 C23 C22 C10 C21 C12 C24 C15 C1 C17 C9 C2 C16 C25 C26 C8 C5 C3 C7 C4 C6
Figure 54. Molecular structure of pyrenophenone (50). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): C(1)– O(1) = 1.2227(15), C(1)–C(2) = 1.4989(17), C(1)–C(21) = 1.4964(18), C(2)–C(3) = 1.3960(18), C(3)– C(4) = 1.3836(19), C(21)–C(26) = 1.3943(19), C(25)–C(26) = 1.393(2); O(1)–C(1)–C(2) = 119.81(11), O(1)– C(1)–C(21) = 120.15(11), C(2)–C(1)–C(21) = 120.04(11).
a)
b)
Figure 55. π–π stacking interactions between two molecules of 50 from a) top view and b) side view.
In the solid state, strong π–π stacking interactions between two neighboring pyrene units can be observed (Figure 55). The pyrene units overlap with approximately 75% of their surface
129 ! ! Results and Discussion ! ! area and an average distance of 3.46 Å can be observed. The plane of the phenyl moiety is 66.2° rotated against the plane formed by the pyrene and blocks further stacking interactions.
Reacting pyrenophenone (50) with ethynylmagnesium bromide in THF leads to the formation of the brownish propargyl alcohol 1-phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51), which can be isolated after aqueous workup (Scheme 61).
H O
1. THF OH 2. H O + H MgBr 2
50 51
Scheme 61. Synthesis of propargyl alcohol 51 starting from pyrenophenone (50).
The addition of the acetylene unit leads to the characteristic acetylene proton at 2.98 ppm and the alcohol proton at 3.86 ppm in the 1H NMR spectrum. In the 13C NMR spectrum the corresponding signals for the acetylene unit appear at 86.7 and 76.8 ppm and the sp3 carbon atom results in a signal at 74.7 ppm. Further proof for the structure are ESI-MS experiments that show the sodium adduct (m/z 355.11 (30%) [M + Na]+) and the IR spectrum that shows a characteristic alkyne absorption at 2114 cm–1.
In the next step the corresponding pyrenophenone based allenylidene complex was synthesized by addition of propargyl alcohol 51 to the complex [Ru(bdmpza)Cl(PPh3)2] (14) in THF and stirring for 4 d at room temperature until a deep red color could be observed (Scheme 62). The separation of the resulting allenylidene complexes
[Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A/54B) was achieved via column chromatography with CH2Cl2/acetone = 1:1 yielding a purple isomer 54A (allenylidene trans to pyrazole) and a red isomer 54B (allenylidene trans to carboxylate). Complex 54A shows
2 13 the Cα carbon atom as doublet at 304.6 ppm ( JC,P = 26.3 Hz) in the C NMR spectrum and the Cβ gives rise to a singlet at 231.2 ppm in the expected region. The PPh3 ligand leads as expected to a singlet in the 31P NMR spectrum at 32.2 ppm. Further proof for the allenylidene moiety is the appearance of a characteristic absorption in the IR spectrum at 1918 cm–1 and
130 ! ! Results and Discussion ! ! the observation of a weak signal during ESI-MS experiments (m/z 960.19 (0.2%) [M]+). The second structural isomer 54B shows downfield shifted values for Cα and Cβ with a doublet at 2 13 315.6 ( JC,P = 19.8 Hz) and a singlet at 241.9 ppm in the C NMR spectrum. Further evidence for the allenylidene complex is the singlet in the 31P NMR spectrum at 32.2 ppm. However, this signal has the identical value as structural isomer 54A and is usually the easiest indicator for the geometry and allows in this case no statement. In the IR spectrum the typical absorption appears at 1916 cm–1 and ESI-MS experiments allowed the observation of the molecular ion (m/z 960.19 (14%) [M]+).
Me Me N N O Me Me Me Me N O N N N N N Ru O O Me Me N O N N O N Cl Ph3P PPh3 Me Ru Me Me Ru Me 14 C THF Ph3P Cl + Ph3P C Cl H C C C C OH
54A
54B
51
Scheme 62. Synthesis of [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A, 54B).
Layering a solution of 54B in CH2Cl2 with n-hexane gave crystals suitable for a single crystal X-ray structure determination. The compound crystallizes as racemic mixture in the space group P–1. A molecular presentation of the compound is illustrated in Figure 56. As mentioned previously for type B isomers the typical strained coordination of the bdmpza can be observed and the allenylidene unit is coordinated trans to a pyrazole leaving the PPh3 ligand trans to the second pyrazole and the chlorido ligand trans to the carboxylate anchor. Furthermore, this structure determination proves that the assignment to the A and B type isomers is correct. The characteristic allenylidene angles are with ∠Ru–C(61)– C(62) = 172.1(2) and ∠C(61)–C(62)–C(63) = 165.7°(3) strongly bent and show values similar to the pentacenequinone based allenylidene complex 29B. In the case of complex 54B the π–
131 ! ! Results and Discussion ! !
π stacking interactions between the neighboring pyrenyl moieties is reduced as the pyrenyl units are showing less than half a pyrene overlap. However, π–π stacking interactions between the pyrenyl moiety and one pyrazolyl unit can be observed, which seems to be responsible for a larger distortion of the bdmpza ligand, the reduced linearity of the allenylidene unit and the reduced planarity of the pyrenyl moiety.
O2
N12 N22
N21 O1 N11 Ru
C72 P1 C61 Cl1 C62 C63
Figure 56. Molecular structure of [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54B). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.1458(19), Ru–N(21) = 2.086(2), Ru–O(1) = 2.1477(16), Ru–P(1) = 2.3521(6), Ru–Cl(1) = 2.3999(7), Ru–C(61) = 1.850(2), C(61)–C(62) = 1.250(4), C(62)–C(63) = 1.366(4); N(11)–Ru– N(21) = 84.67(8), O(1)–Ru–N(11) = 84.85(7), O(1)–Ru–N(21) = 87.18(7), O(1)–Ru–P(1) = 86.81(5), P(1)–Ru– Cl(1) = 87.93(2), P(1)–Ru–C(61) = 95.68(7), O(1)–Ru–C(61) = 176.51(9), N(11)–Ru–P(1) = 171.03(6), N(21)– Ru–Cl(1) = 173.29(5), Cl(1)–Ru–C(61) = 91.96(8), Ru–C(61)–C(62) = 172.1(2), C(61)–C(62)– C(63) = 165.7(3).
The reduced planarity is apparent for C(72), the carbon atom that connects the pyrenyl unit to
Cγ, as it deviates from the plane calculated for all pyrenyl carbon atoms by 0.16 Å. The mean distance between the pyrazolyl moiety and the plane calculated for the pyrenyl moiety is 3.48 Å, indicating the strong interactions possible for the pyrene unit. The arrangement
132 ! ! Results and Discussion ! ! suggests that the pyrenyl moiety should allow further π–π stacking interactions with carbon allotropes in solution. However, the solubility is limited to polar solvents like acetone,
CH2Cl2, CHCl3 and mixtures containing aforementioned solvents and nonpolar solvents like n-hexane and n-pentane as apparently the pyrenyl unit reduces the polarity of the complex in comparison to the quinone based allenylidene complexes.
Cyclic voltammetric analyses were again performed on the pyrenophenone based allenylidene complexes 54A and 54B (Chapter 8.2). Both compounds show a behavior similar to the benzotetraphene based allenylidene complexes [Ru(bdmpza)Cl(═C═C═C(BT))(PPh3)] (37A, 37B). The oxidation process involving the ruthenium(II) center appears at 252 mV (54A) or 320 mV (54B). For 54A this process is reversible, however, for 54B this process is irreversible and followed by a second oxidation process at higher potential that shows no backward peak. The reduction processes are all best described as irreversible as the forward scan shows signals similar to the previously reported allenylidene complexes within this work. The backward scan however, shows extremely weak current intensities with larger peak separations.
The UV/Vis spectra of the pyrenophenone based complexes 54A and 54B recorded in CH2Cl2 share several common features with the other ruthenium allenylidene complexes bearing the bdmpza ligand (Figure 57). The strong absorptions at wavelengths less than ~300 nm have been assigned to ligand-centered (LC) π–π* transitions involving the PPh3 and bdmpza ligands. However, the intense absorption around 330 nm (54A: 336 nm, 29000 L mol–1 cm–1; 54B: 335 nm, 27000 L mol–1 cm–1) seems to correspond to the parent pyrenophenone moiety 50. An additional metal-perturbed π–π* transition can be observed at 543 nm for 54A with a molar extinction coefficient around 24000 L mol–1 cm–1. This extinction coefficient is noticeably larger in comparison to the allenylidene complexes discussed so far, although the absorption maximum is close to the diphenyl based allenylidene complex
–1 –1 [61] [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)] (519 nm, 17000 L mol cm ). In comparison to the complex of type A, complex 54B shows with an absorption at 523 nm a decrease in absorption energy and the extinction coefficient (19000 L mol–1 cm–1) is in the common range if compared to 37A. Again absorption bands are observed in the NIR region around 1050 nm (45A) and 900 nm (45B) that can be attributed to HOMO–LUMO transitions and can best be described as MLCTs (Figure 58).
133 ! ! Results and Discussion ! !
40000
30000 ] /1 * )cm /1
20000 )[L)mol ε )
10000
0
300 400 500 600 700
Wavelength)[nm]
Figure 57. Absorption spectrum of 54A (black) and 54B (grey) in CH2Cl2; signal caused by switching lamp is indicated by *.
200
180
160
140 ] 01 120 *cm 01 100
80 *[L*mol ε * 60 *
40 *
20 *
0 800 900 1000 1100 1200 1300
Wavelength*[nm]
Figure 58. Magnification of the relevant parts of the NIR region displaying forbidden MLCTs for of 54A (black)
and 54B (grey); signal caused by CH2Cl2 is indicated by *.
134 ! ! Results and Discussion ! !
4.5.3 Carbon-Rich Ruthenium Allenylidene Complexes Bearing the PTA Ligand
For possible applications of the carbon-rich allenylidene complexes, e.g. in the exfoliation of carbon allotropes, solubility in aqueous media or at least in alcohols is required. Hence, it was decided to adapt the ligand sphere of the ruthenium precursor to allow the formation of water- soluble allenylidene complexes.
Two types of water-soluble phosphines are commonly used in organometallic chemistry. On the one hand, sulfonated derivatives of the classical triphenylphosphine ligand like the triphenylphosphine-3,3′,3′′-trisulfonic acid trisodium salt (TPPTS) and on the other hand the adamantane derived 1,3,5-triaza-7-phosphaadamantane (PTA). For ruthenium allenylidene complexes, especially the PTA ligand has proven successful, as the cyclopentadienyl and
[348] hydridotrispyrazolyl based complexes [Ru(Cp)(═C═C═CPh2)(PTA)(PPh3)](CF3SO3) and [261] [Ru(Tp)(═C═C═CPh2)(PTA)(PPh3)]PF6 have been reported. Precursors for these [349] complexes are the chlorido complexes [Ru(Cp)Cl(PTA)(PPh3)] and [Ru(Tp)Cl- [350] (PTA)(PPh3)]. Reaction of the latter with propargyl alcohols led to the formation of cationic allenylidene complexes due to chloride abstraction. As for the bdmpza based ruthenium triphenylphosphine complex [Ru(bdmpza)Cl(PPh3)2] (14) usually one phosphine ligand can be replaced easily, it was decided to synthesize the PTA analogues
[Ru(bdmpza)Cl(PTA)(PPh3)] (55) and [Ru(bdmpza)Cl(PTA)2] (56), each (Scheme 63).
135 ! ! Results and Discussion ! !
Me Me N N O N O N Me Ru Me + 1.0 eq. PTA Ph3P Cl P - PPh3 55 N N Me Me N N N O N O N Me Me Me Ru Me N N O N O N Ph3P Cl PPh3 + 2.2 eq. PTA Me Ru Me
- 2 PPh3 P Cl P
N N N N N N 56
Scheme 63. Synthesis of [Ru(bdmpza)Cl(PTA)(PPh3)] (55) and [Ru(bdmpza)Cl(PTA)2] (56).
The reaction of [Ru(bdmpza)Cl(PPh3)2] (14) with one equivalent PTA in THF under reflux allows the almost quantitative exchange of one PPh3 ligand. Complex 55 shows in the IR –1 1 spectrum the characteristic carboxylate absorption at 1661 cm in CH2Cl2. The H NMR spectrum shows two multiplets around 7.66 and 7.26 ppm that can be assigned to the PPh3 ligand and the PTA ligand leads to four quartets showing an AB pattern in the aliphatic region at 4.37, 4.23, 3.89 and 3.78 ppm. The bdmpza ligand exhibits two asymmetric protons in the 4- and 4´ position indicating the expected asymmetric structure. The 13C NMR spectrum repeats the conclusions drawn from the proton NMR spectrum as the characteristic doublets
3 1 from the PTA ligand at 73.1 ( JC,P = 5.8 Hz) and 52.4 ppm ( JC,P = 14.8 Hz) can be observed as well as four asymmetric methyl substituents at 16.7, 14.0, 11.5 and 11.5 ppm. Further
31 evidence is the coupling pattern in the P NMR spectrum showing one doublet of the PPh3 2 ligand at 41.2 ppm ( JP,P = 43.5 Hz) and one doublet of the PTA ligand at –27.5 ppm 2 ( JP,P = 43.5 Hz) caused by the two different phosphine ligands. Additional ESI-MS experiments show the presence of the molecular ion as major observable compound (m/z 803.17 (100%) M+). Complex 55 is nicely soluble in polar solvents like chlorinated solvents, THF and alcohols, but unfortunately insoluble in water.
136 a c b
! ! Results and Discussion ! !
O2
N12 N22
O1 N11 N21
Ru P1
P2 Cl1
Figure 59. Molecular structure of [Ru(bdmpza)Cl(PTA)(PPh3)] (55). Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru–N(11) = 2.184(3), Ru–N(21) = 2.184(3), Ru–O(1) = 2.112(2), Ru–P(1) = 2.2621(10), Ru–P(2) = 2.3027(10), Ru–Cl(1) = 2.4048(9); N(11)–Ru–N(21) = 79.22(11), O(1)–Ru–N(11) = 87.42(10), O(1)–Ru– N(21) = 86.97(10), O(1)–Ru–P(1) = 86.90(7), P(1)–Ru–Cl(1) = 93.08(4), P(1)–Ru–P(2) = 91.86(4), N(11)–Ru– P(1) = 170.19(8), N(21)–Ru–Cl(1) = 88.84(8).
Crystals of 55 suitable for single crystal X-ray structure determination could be obtained from
a concentrated solution in CH2Cl2 layered with n-hexane (Figure 59). The complex
crystallizes as enantiomeric mixture in space group Pbca with one co-crystalized CH2Cl2 per
asymmetric unit. As expected the PPh3 and PTA ligand are similar to the parent ruthenium
complex [Ru(bdmpza)Cl(PPh3)2] (14) positioned trans to the pyrazolyl moieties, thus the chlorido ligand is positioned trans to the carboxylate anchor. The smaller Tolman cone angle
and the resulting reduced steric demand of the PTA ligand in comparison to the PPh3 ligand leads to a Ru–P(1) bond length of 2. 2621(10) Å and a longer Ru–P(2) bond length of 2.3027(10) Å. The reduced repulsion between the two phosphine ligands is also responsible
for a smaller angle ∠O(1)–Ru–P(1) = 86.90(7)° in comparison to the larger PPh3 ligand with the angle ∠O(1)–Ru–P(2) = 93.20(7)°. The angle between both phosphine ligands is in
consequence reduced from 94.12(6)° for [Ru(bdmpza)Cl(PPh3)2] (14) to 91.86(4)° for
137 ! ! Results and Discussion ! ! complex 55.[61] However, the rigid structure of the bdmpza ligand leads to an almost symmetrical coordination of the bdmpza ligand with identical ruthenium–nitrogen bond lengths of 2.184(3) Å for Ru–N(11) and Ru–N(12).
In analogy the synthesis of [Ru(bdmpza)Cl(PTA)2] (56) was attempted starting from
[Ru(bdmpza)Cl(PPh3)2] (14) with two equivalents PTA either in THF or toluene under reflux.
The reaction formed a mixture of 56 and [Ru(bdmpza)Cl(PTA)(PPh3)] (55). Employing 2.2 equivalents of PTA and longer reaction times in THF under reflux led to a full conversion to 56. However, it was not possible to purify complex 56 convincingly as the excess amounts of PTA could not be removed. Complex 56 shows high solubility in water as expected from the
[351] 1 similar cyclopentadienyl ruthenium complex [Ru(Cp)Cl(PTA)2]. The H NMR spectrum shows a triplet at 4.17 and a multiplet around 4.01 ppm that can be assigned to the two coordinated PTA ligands. The signals of the bdmpza ligand seem to indicate that the reduced steric demand of the PTA ligand might allow a dynamic exchange between the two PTA ligands and the chlorido ligand as for the protons in position 4 of the pyrazole moiety only one signal at 5.79 ppm can be observed but the four methyl substituents lead to one singlet consisting of two methyl substituents at 1.80 ppm and two further singlets at 2.12 and 2.21 ppm representing one methyl group each. The 13C NMR spectrum shows a symmetrical complex as only one set of signals can be observed as the Me3 and Me3´ substituents give one signal at 13.6 ppm and in consequence the Me5 and Me5´ substituents lead to one signal at 11.6 ppm. In the 31P NMR spectrum a triplet of the PTA ligand at –53.8 ppm can be observed that cannot be conclusively explained by the suspected structure. Preliminary experiments showed that the reaction of 56 with 9-ethynyl-9-fluorenol does not allow the formation of allenylidene complexes as the formation of a complicated mixture of compounds can be observed. The hot reaction mixture shows an intense red color that disappears upon cooling to room temperature, which is in good agreement with previous reports. According to these,
PTA, if present in solution, can add to Cα of allenylidene ligands hereby forming an α- [352] phosphonioallenyl species. Hence it was decided to focus on [Ru(bdmpza)Cl(PTA)(PPh3)]
(55) as precursor as the reaction with propargyl alcohols should displace the PPh3 ligand that has previously not shown any addition reactions to the allenylidene moiety.
Reacting 55 with twofold excess of 9-ethynyl-9-fluorenol in THF at room temperature for two days did not lead to any formation of an allenylidene complex in contrast to the
[Ru(bdmpza)Cl(PPh3)2] (14) based fluorenyl substituted complex [Ru(bdmpza)Cl-
(═C═C═(FN))(PPh3)] (7A/7B). However, heating to reflux for 16 h allowed the formation of 138 ! ! Results and Discussion ! ! a deep red allenylidene complex [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B) that upon heating for further 24 h under nitrogen atmosphere decomposes (Scheme 64). The implementation of the polar PTA ligand led to a strongly decreased Rf value for the
CH2Cl2/acetone eluent mixture for column chromatography, which is usually employed in the purification of bdmpza based allenylidene complexes. Therefore, a solvent mixture of acetone/water (95:5 v/v) was used to separate the allenylidene complexes from the crude product, yielding two fractions. The first purple complex was assigned to the structure 57A and the second red complex was assigned to 57B. Due to the extremely low yields, i.e. 11% for 57A and below 1% for 57B, only complex 57A could be characterized satisfyingly.
–1 Complex 57A shows the typical IR absorption at 1923 cm in CHCl3 indicating the successful formation of an allenylidene complex. In the 1H NMR spectrum the asymmetric bdmpza ligand can be observed, as four methyl substituents are present at 2.89, 2.58, 2.51 and 2.24 ppm. The PTA ligand is characterized by one singlet at 4.52 ppm and a doublet at
2 13 4.24 ppm ( JH,H = 6.8 Hz). In the C NMR spectrum the allenylidene moiety is 2 unambiguously assigned to the doublet at 294.2 ppm ( JC,P = 26.0 Hz, Cα) and a singlet at
230.3 ppm (Cβ). The remaining aromatic protons can be assigned to the fluorenyl moiety and the bdmpza ligand confirms the asymmetric pattern with four different chemical shifts of 16.1, 13.0, 11.5 and 11.3 ppm. The PTA ligand shows the expected two doublets at 73.8
3 1 ( JC,P = 6.0 Hz, N–CH2–N) and 52.1 ppm ( JC,P = 18.0 Hz, P–CH2–N) confirming free rotation around the Ru–P bond in the NMR timescale. A strong indication for the assignment of the obtained complex is the splitting of the signal of the carbon atom in 4 position of the pyrazole
4 4 moiety. This behavior leading to a doublet at 108.4 ppm ( JC,P = 2.7 Hz, C ) is commonly observed for type A isomers of bdmpza based ruthenium cumulenylidene complexes (for comparison see: 49, 54A). Finally the 31P NMR spectrum shows one singlet at –37.8 ppm, which provides further proof that the PPh3 ligand has been replaced and only the PTA ligand is present in complex 57A.
139 ! ! Results and Discussion ! !
Me Me N N O N O N Me Ru Me Me Me Me Me Ph P Cl P N N N N 3 O O N O N N O N 55 N N N Me Ru Me Me Ru Me + PTA Cl C + PTA C Cl THF C H C C C
OH 57A 57B
Scheme 64. Synthesis of [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A, 57B).
The comparison of the solubility between [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (7A/7B) and
[Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A) shows that the exchange of the PPh3 ligand with PTA increases the solubility of allenylidene complex 57A in polar solvents like ethanol and methanol. However, the exchange does not significantly increase the solubility in water as only aqueous solutions with approximately 10 vol% DMSO were stable for extended periods of time without precipitation.
In analogy to the synthesis described above, a reaction of 1-phenyl-1-(pyren-1-yl)prop-2-yn-
1-ol (51) with [Ru(bdmpza)Cl(PTA)(PPh3)] (55) was examined (Scheme 65). In theory the targeted allenylidene complex could exfoliate carbon allotropes in a wide range of polar solvents if a similar solubility to 57A could be achieved. The reaction mixture was again heated for 16 h under reflux and a complicated mixture of complexes was obtained. The previously described complex [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A/54B) and the carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] could be easily removed via column chromatography with CH2Cl2/acetone (1:1 v/v) as eluent. The desired complex [Ru(bdmpza)- Cl(═C═C═C(PyrPh))(PTA)] (58A/58B) could be eluted with a solvent mixture of acetone/methanol (9:1 v/v) in poor yields. 58A was obtained as purple compound in 5% yield allowing the characterization by spectroscopic methods.
140 ! ! Results and Discussion ! !
Me Me N N O N O N Me Ru Me Me Me Me Me Ph P Cl P N N N N 3 O O N O N N O N 55 N N N Me Ru Me Me Ru Me + PTA Cl C + PTA C Cl THF C H C C C
OH 58A
58B
51
Scheme 65. Synthesis of [Ru(bdmpza)Cl(═C═C═C(PyrPh))(PTA)] (58A, 58B).
The strong purple color of the obtained complex as well as the characteristic absorption at
–1 1919 cm in CHCl3 indicate the successful formation of an allenylidene complex. The NMR data recorded was assigned to a type A isomer. In the 1H NMR spectrum, the aromatic protons can be observed between 8.50 and 7.32 ppm similar to the complex [Ru(bdmpza)Cl-
(═C═C═C(PyrPh))(PPh3)] (54A/54B). The PTA ligand shows one doublet at 4.14 ppm 2 ( JH,H = 13.1 Hz) that consists of three protons and a multiplet around 3.94 ppm consisting of nine protons. In comparison to complex 57A this indicates a reduced symmetry of the PTA ligand and possibly a hindered rotation around the Ru–P axis due to the sterically demanding pyrenyl moiety. Furthermore the methyl substituents of the bdmpza ligand are spread over a wider range in the 1H NMR spectrum at 2.78, 2.51, 2.29 and 1.97 ppm. In the 13C NMR spectrum the allenylidene moiety leads to signals in the expected region with a doublet at
2 300.6 ppm ( JC,P = 26.3 Hz, Cα) and a singlet upfield shifted at 228.0 ppm (Cβ). As described for complex 57A the splitting of the carbon signal in 4 position of the pyrazole moiety at
4 4 108.0 ppm ( JC,P = 3.5 Hz, C ) confirms the assignment to the suggested structure. The PTA 13 3 ligand is, in the C NMR spectrum, symmetrical with two doublets at 73.3 ( JC,P = 6.1 Hz, N– 1 CH2–N) and 52.0 ppm ( JC,P = 17.5 Hz, P–CH2–N) indicating that the unexpected results of the 1H NMR spectrum indicate a dynamic behavior of the PTA ligand. The shorter relaxation
141 ! ! Results and Discussion ! !
1 13 times of the H nuclei in comparison to the C nuclei might explain the difference in the observed symmetry in solution. The 31P NMR spectrum shows a series of multiplets indicating possible protonation equilibria in solution resulting in unsymmetrical PTA ligands. Furthermore, ESI-MS experiments detected the corresponding molecular ion (m/z 803.17 (100%) [M]+).
As can be seen from the solvents used for column chromatography the larger pyrenyl substituent decreases the solubility in highly polar solvents like water. Complex 58A shows high solubility in ethanol and methanol but is completely insoluble in water. Furthermore, the combination of the smaller PTA ligand in comparison to PPh3 and the large pyrenyl substituent decreases the stability of complex 58A. The PPh3 based complex
[Ru(bdmpza)Cl(═C═C═C(PyrPh))(PPh3)] (54A) is stable in CH2Cl2 solution for several weeks without any noticeable decomposition. The PTA based complex [Ru(bdmpza)Cl-
(═C═C═(FN))(PTA)] (57A) did not show any signs of decomposition within days in CH2Cl2. However, complex 58A completely decomposes under aerobic conditions in less than three days and possibly forms a complex [Ru(bdmpza)Cl(CO)(PTA)] (59) as indicated by the
–1 appearance of an IR absorption band at 1979 cm in CHCl3. This value is in good agreement with the comparable carbonyl complexes [Ru(Tp)Cl(CO)(PTA)][352] (1963 cm–1 (KBr)) and
[61] –1 [Ru(bdmpza)Cl(CO)(PPh3)] (1969 cm (CH2Cl2)).
While the synthesis of PTA substituted bdmpza based ruthenium allenylidene could be demonstrated the low yields, the reduced stability and the remaining insolubility in water is a major drawback. Therefore, water-soluble carbon-rich ruthenium allenylidene complexes bearing the bdmpza ligand seem inconvenient and the use of cationic Cp based allenylidene complexes might be required. Thus complexes of the general formula
– [Ru(Cp)(═C═C═CAr2)(PPh3)(PTA)]X or [Ru(Cp)(═C═C═CAr2)(PTA)2]X (X = PF6 , – CF3SO3 ) might be target molecules for future studies.
142 ! ! Results and Discussion ! !
4.6 Arenium Cation or Radical Cation Pathway: Mechanistic Analysis and Experimental Proof of the Scholl Reaction of Pyrenophenone
The first report on oxidative coupling was published in 1868 by J. LÖWE,[353] 42 years later
R. SCHOLL reported that anhydrous AlCl3 was a suitable medium for several aromatic compounds to undergo oxidative coupling.[295] Given the recent interest in polycyclic aromatic hydrocarbons (PAHs) oxidative aromatic coupling reactions and the classical Scholl Reaction have been extensively reviewed by H. BUTENSCHÖN and D. GRYKO.[354] The difference between both reactions has since the earlier review by A. BALABAN and C. NENITZESCU lost a clear demarcation as the term Scholl reaction is oftentimes used as synonym for oxidative coupling reactions of electron-rich aromatic compounds.[355]
The versatility of the reaction parameters has allowed the formation of up to 126 bonds in one step as reported by K. MÜLLEN and co-workers.[356] The broad applications for intramolecular C–C bond formation has been demonstrated in a series of papers. One of the most prominent PAHs remains hexa-peri-benzocoronene (HBC), which can be obtained via different precursors,[357-359] but also the intermediary phenyldibenzo[fg,ij]phenanthro[9,10,1,2,3- pqrst]pentaphene could be isolated,[360] which indicates a stepwise reaction mechanism in comparison to a concerted planarization. For the reaction mechanism, two pathways are discussed in dependence of the substrate and reaction conditions in literature. On the one hand, the Arenium Cation Pathway, which has been calculated by B. KING as favourable
[361-363] pathway for the formation of HBC with oxidizing agents like FeCl3, and on the other hand, the Radical Cation Pathway, which is reported by R. RATHORE for DDQ as oxidant.[364-
365] H. BUTENSCHÖN and D. GRYKO concluded their review about the mechanistic debate with the statement that the Arenium Cation Mechanism might be operating in the presence of
[354] strong Lewis acids like AlCl3 as isolated intermediates are still missing.
As mentioned earlier the Scholl reaction of pyrenophenone (50) is known to literature, however, the results obtained differ significantly from the literature and will be discussed in detail in the following section.
The first report on the reaction of pyrenophenone (50, see Scheme 66) in a mixture of
AlCl3/NaCl was in 1937, when H. STREECK and H. VOLLMANN demonstrated that these [345] conditions were favourable to the previously employed pure AlCl3. After complicated
143 ! ! Results and Discussion ! ! workup they obtained a yellow ketone that they described as 60. However, S. DICKERMAN and
W. FEIGENBAUM revaluated the obtained compound in 1966 and proposed that the given structure is not in agreement with the IR spectrum obtained, as the keto moiety shows an
–1 absorption at 1695 cm in CHCl3 representative for a 9-fluorenone, indicating that the compound 64 was obtained.[347] C. RÜCHARDT and co-worker prepared the same compound after a “cumbersome workup” in 1999 and assigned it in analogy to the original report to structure 60.[291]
O O
50 60 +HCl Radical Cation -e- Arenium Cation Pathway -Cl- Pathway
O O
65 61
H H
O O
66 62
H H H H +Cl- - -HCl, -H +Cl -HCl
O O
64 63 - H2 ∗ C H 2
Scheme 66. Radical Cation and Arenium Cation Pathway for the intramolecular Scholl Reaction of pyrenophenone (50).
Hence, the synthesis was performed according to the original literature procedure starting from pyrenophenone (50).[345] However, during workup several well-ordered aliphatic protons
144 ! ! Results and Discussion ! ! were observed in the 1H NMR spectrum of the crude product that could not be explained by the proposed products. Several steps of column chromatography allowed the isolation of compound 64 in low yields, which shows identical spectroscopic properties to the data reported by C. RÜCHARDT, S. DICKERMAN and W. FEIGENBAUM.[291, 347] A single crystal X-ray structure determination of 64 confirmed the suggested formation of a five-membered ring
(Figure 60), as opposed to the initially reported six-membered ring by H. VOLLMANN et al.[345]
11H-indeno[2,1-a]pyren-11-one (64) crystallizes in space group P212121 as planar compound with an almost symmetrical cyclopentanone ring.
O1
C14 C22 C1 C13
C23 C21 C15 C11 C2 C12 C24 C26 C3 C17 C16 C25 C4 C10 C5 C9 C8 H4 C7 C6
Figure 60. Molecular structure of 64. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths (Å) and angles (deg): C(1)–O(1) = 1.213(3), C(1)–C(2) = 1.499(4), C(1)–C(21) = 1.485(4), C(2)– C(3) = 1.399(4), C(3)–C(4) = 1.378(4), C(21)–C(26) = 1.413(4), C(25)–C(26) = 1.379(4); O(1)–C(1)– C(2) = 128.0(3), O(1)–C(1)–C(21) = 126. 5(3), C(2)–C(1)–C(21) = 105.5(2).
A second red slightly fluorescent compound could be isolated that was responsible for the previously observed aliphatic proton signals. The structure could be unambiguously assigned to the racemic mixture of compound 63 via 1H and 13C NMR spectroscopy, IR spectroscopy, mass spectrometry and a single crystal X-ray structure determination. The compound crystallizes in space group Pna21 as enantiomeric pure form and is depicted as (S)-enantiomer in Figure 61. Since no heavy atoms but only oxygen, carbon and hydrogen atoms are present, based on the Flack parameter no reliable decision regarding the stereochemistry can be made. In comparison to 64 compound 63 shows a reduced pyrenyl moiety leading to a non-planar geometry with an angle of 108.9° between the methylene carbon atom and its neighbouring carbon atoms.
145 ! ! Results and Discussion ! !
O1 C13 C14 C1 C11 C22 C15 C12 C21 C10 C2 C17 C23 C26 H3 C16 C24 C3 C5 C8 C9 C25 C6 C4 C7 H4A H4B
Figure 61. Molecular structure of 63 depicted as (S)-enantiomer. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths (Å) and angles (deg): C(1)–O(1) = 1.222(3), C(1)–C(2) = 1.476(4), C(1)–C(21) = 1.490(4), C(2)–C(3) = 1.525(4), C(3)–C(4) = 1.493(5), C(21)–C(26) = 1.398(4), C(25)– C(26) = 1.380(4); O(1)–C(1)–C(2) = 128.5(3), O(1)–C(1)–C(21) = 126.1 (3), C(2)–C(1)–C(21) = 105.4(2).
As indicated in the introduction, it is commonly accepted as working theory and backed by computational studies for the Scholl reaction that the Arenium Cation Mechanism is favoured in the presence of AlCl3. Compound 63 is however, the first isolated intermediate that unambiguously can be assigned to the Arenium Cation Pathway as no protonation in the 6-postion of the pyrenyl moiety can be explained via the Radical Cation Pathway (Scheme
66). Previous reports have shown that the presence of HCl in AlCl3 leads to the initial protonation of pyrenophenone (50) forming cation 61.[366] After C–C bond formation cation 62 is deprotonated at the phenyl moiety to regain aromaticity and leads to the partially reduced pyrenyl moiety in compound 63. This protonation-deprotonation cycle is in good agreement with an expected catalytic protonation step that has been previously calculated. Apparently, the oxidation step to obtain compound 64 under dehydrogenation appears only partially, explaining the low yields that were reported previously. In addition to the described products, large amounts of black insoluble residue, unsubstituted pyrene and dibenzoylpyrene can be observed confirming a series of side reactions. Currently calculations are performed by
C. WICK form the group of T. CLARK at the CCC (Computer Chemie Centrum) to gain further insights into the transition states and possible radical intermediates.
146
5 SUMMARY AND OUTLOOK
147 ! ! Summary and Outlook ! !
In previous work of the BURZLAFF group, the design of suitable N,N,O ligands for a wide variety of applications ranging from catalysis to bioinorganic model compounds has been extensively investigated. Especially the methyl substituted bis(3,5-dimethylpyrazol-1-yl) acetate (bdmpza) ligand has shown manifold chemistry, comparable to the anionic cyclopentadienyl (Cp) and hydridotris(pyrazol-1-yl)borato (Tp) ligand.
In the first part of this thesis the new tricarbonylmanganese(I) complexes bearing the heteroscorpionate ligand 3,3-bis(3,5-dimethylpyrazol-1-yl)propionate (bpzp) and the tris- imidazole complex [Mn(CO)3(HIm)3]Br were prepared. These and the literature-known tricarbonyl complexes based on bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza), bis(pyrazol-
1-yl)acetate (bpza), 3,3-bis(3,5-dimethylpyrazol-1-yl)propionate (bdmpzp) and [MnBr(CO)3-
(Hpz)2] were tested for their potential to act as photoactivable CO-releasing molecules (PhotoCORMs) by the UV/Vis spectroscopy-based myoglobin assay. The manganese(I) complexes of the monodentate imidazole and pyrazole ligands lack stability in solution and show fast CO-release already in the dark. In the four heteroscorpionate complexes, the substitution pattern and the chain length of the carboxylate moiety have a pronounced influence on the stability in solution and the CO-release properties.
The second part of this work contains the synthesis and characterization of ruthenium carbonyl complexes bearing heteroscorpionate ligands and was accomplished in collaboration with S. TAMPIER and G. TÜRKOGLU. The syntheses of the two dicarbonyl complexes!
[Ru(bdmpza)Cl(CO)2] (9) and [Ru(2,2-bdmpzp)Cl(CO)2] (10), !bearing a bis(3,5- dimethylpyrazol-1-yl)acetato (bdmpza) or a 2,2-!bis(3,5-dimethylpyrazol-1-yl)propionato
(2,2-bdmpzp) scorpionate! ligand, have been previously described by S. TAMPIER and
G. TÜRKOGLU and following the same procedure the bis(pyrazol-1-yl)acetato (bpza) based complex has been obtained. All three complexes were synthesized by reacting the! polymer
[RuCl2(CO)2]n with the potassium salt of the corresponding ligand (K[bdmpza], K[bpza] or
K[2,2-bdmpzp]). !Reaction of the acid Hbdmpza with [Ru3(CO)12] resulted in the !formation of two structural isomers of a hydrido complex, [Ru!(bdmpza)H(CO)2] (11A/11B). Under aerobic conditions the conversion of! [Ru(bdmpza)H(CO)2] (11A/11B) to form the Ru(I) dimer 5 [Ru(bdmpza)(CO)(μ2-CO)]2 (12) seems to be hindered compared to the η -C5H5 (Cp) analogues. Dimer 12 was obtained via reaction of! Hbdmpza with catena-[Ru(OAc)(CO)2]n instead.
148 ! ! Summary and Outlook ! !
In the third part, a topic with bioinorganic focus was described. The reaction of
[Ru(bdmpza)Cl(PPh3)2] with aminophenol (APH) and 2-amino-4,6-di-tert-butylphenol tBu ( APH) led to the corresponding complexes [Ru(bdmpza)Cl(ISQ)(PPh3)] or tBu [Ru(bdmpza)Cl(IBQ)(PPh3)] (16) and [Ru(bdmpza)Cl( ISQ)(PPh3)] or [Ru(bdmpza)Cl-
tBu 1 ( IBQ)(PPh3)] (15). In both complexes the uncommon κ coordination of the imino moiety was observed and not the expected κ2 N,O coordination. From the single crystal X-ray structure determination and the diamagnetic NMR spectra it was concluded that the complex could best be described as [Ru2+–IBQ] or [Ru3+–ISQ] with strong antiferromagnetic coupling. This gives rise to the question of the occurring redox chemistry as future work will have to determine the dependence of the reaction on oxidizing agents and in consequence an optimization of the reaction.
Me Me Me Me N N N N O O N O N N O N Me Ru Me or Me Ru Me NH NH O O Ph3P Cl Ph3P Cl
R R R R 15 (IBQ); R = tBu 15 (ISQ); R = tBu 16 (IBQ); R = H 16 (ISQ); R = H
In the main part of this work a series of ruthenium allenylidene complexes bearing polyaromatic substituents was prepared starting from [Ru(bdmpza)Cl(PPh3)2] (14). Reacting 14 with 1,1-bis-(3,5-di-tert-butylphenyl)-1-methoxy-2-propyne results in the formation of two
t structural isomers of an allenylidene complex [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)]
(19A/19B) and the related carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)] (18A/18B). Conversion of 9-ethynyl-9-fluorenol led to the corresponding allenylidene complex
[Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B) (FN = fluorenyl). Based on anthraquinone a new synthetic route towards 10-ethynyl-10-hydroxyanthracen-9-one via the TMS protected propargyl alcohol is described. Starting thereof, the synthesis of the allenylidene complex
([Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B) (AO = anthrone) is reported and showed interesting π-π stacking interactions in the solid state between two anthrone units. In a next step the larger acene pentacenequinone was used as starting material in cooperation with A.
149 ! ! Summary and Outlook ! !
WATERLOO of the group of R. TYKWINSKI to synthesize [Ru(bdmpza)Cl(═C═C═(PCO))-
(PPh3)] (29A/29B) (PCO = pentacenone). In comparison with other ruthenium allenylidene complexes, the Ru–C3 chain was extremely bent and these distorted angles, which were unprecedented for mononuclear ruthenium allenylidene complexes, might have be caused by crystal packing effects. As again only dimerization in the solid state could be observed, it was decided to use polyaromatic ketones with extended π systems along the allenylidene direction. As suitable compound 7H-benzo[no]tetraphen-7-one (34) was used and the route from 34 towards the propargyl alcohol 7-ethynyl-7H-benzo[no]tetraphen-7-ol (36) and the transformation into the allenylidene complex [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B) (BT = benzotetraphene) was described. Especially complex 37A is a promising candidate for future studies metal-tuned FET studies, since several short-contact interactions between the benzotetraphene throughout the entire crystal could be observed possibly allowing charge transport along this axis. All aforementioned complexes showed weak absorptions in the NIR region that could be assigned to forbidden MLCT transitions.
tBu tBu
tBu tBu 20A/20B 19A/19B Me Me N N O N O N Me Ru Me
C CR2 = Ph3P Cl CR2 O O 25A/25B 29A/29B
H CN CN
NC CN 31 37A/37B
150 ! ! Summary and Outlook ! !
TD-DFT calculations that were performed by E. HÜBNER starting from the single crystal X- ray structure determinations proved this assignment to transitions involving mainly the HOMO–2, HOMO–1, HOMO and LUMO. In addition cyclic voltammetry has been used to probe the electrochemistry of each complex. In summary, it was shown that the arrangement observed for several compounds in the crystalline state renders the presented complexes promising candidates for metal-tuned FETs or “organic” metal–semiconductor field-effect transistors (OMESFETs), whereas the electron-accepting ability and low-energy absorption characteristics might be tuned for an application in solar cells. Both aspects present an appealing starting point for new kinds of functionalized organic semiconductors. In an attempt to obtain an allenylidene complex starting from 2-(13-(dicyanomethyl)-13- ethynylpentacen-6(13H)-ylidene)malononitrile (30), the corresponding vinylidene complex
[Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (PCN = pentacenone based tetracyano derivative) (31) was isolated. The strong push-pull character of the cyano substituents leads to an intensive blue color of the vinylidene complex 31. For comparisons and possible catalytic applications the 16 VE ruthenium allenylidene complexes [RuCl2(═C═C═(FN))(PPh3)2] (45),
[RuCl2(═C═C═(AO))(PPh3)2] (46) and [RuCl2(═C═C═(PCO))(PPh3)2] (47) were prepared. However, in solution all three showed the tendency to form a mixture of a cationic and a neutral dimeric 18 VE complex, leading to an unfavorable equilibrium.
Me Me Me Me Me Me N N N N N N O O O N O N N O N N O N Me Ru Me Me Ru Me Me Ru Me PPh Cl C PTA Cl C PTA Cl C 3 C C C C C C
54A 57A 58A
The work presented in the next chapter focuses on the preparation of ruthenium cumulenylidene complexes that might be suitable for exfoliation of carbon nanotubes. Therefore, the two vinylidene complexes [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))-
(PPh3)] (48) and [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) were prepared. While remarkably stable for ruthenium vinylidene comlexes, the degradation within days was a major drawback
151 ! ! Summary and Outlook ! ! for both complexes. Therefore, the idea was to again focus on allenylidene complexes and in this case the pyrene substituted propargyl alcohol 1-phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51) was prepared from pyrenophenone (50). The corresponding ruthenium allenylidene complex
[Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B) was isolated and showed absorption propeties closely related to the complex [Ru(bdmpza)Cl(═C═C═CPh2)-(PPh3)], indicating that no conjugation between the allenylidene moiety and the pyrene substituent was present. To enhance the solubility of the allenylidene complexes in polar protic solvents, the exchange of the PPh3 ligand with the PTA ligand (1,3,5-triaza-7-phosphaadamantane) was investigated. While the complexes [Ru(bdmpza)Cl(═C═C═(FN))-(PTA)] (57A) and [Ru(bdmpza)Cl-
(═C═C═C(PhPyr))(PTA)] (58A) could be prepared from [Ru(bdmpza)Cl(PTA)(PPh3)] (55), the stability was strongly decrased, leaving both complexes unsuitable for further applications. In the future, especially complex 54A/54B should be studied for possible non- covalent functionalizations of carbon nanotubes in polar solvents.
In the last chapter, the intramolecular Scholl Reaction of pyrenophenone (50) was discussed in detail. Opposing to the literature the extended polyaromatic compound could be unambiguously identified as 11H-indeno[2,1-a]pyren-11-one (64). Furthermore, the possible intermediary reduced compound 6,6a-dihydro-11H-indeno[2,1-a]pyren-11-one (63) could be isolated. Currently calculations are performed in the CLARK group by C. WICK to understand the mechanistic pathway from 50 to 64 and to see if the Arenium Cation Pathway is suitable or radical intermediates are preferred. O O O
∗ C 50 H2 64 63
152
6 ZUSAMMENFASSUNG UND AUSBLICK
153 ! ! Zusammenfassung und Ausblick ! !
In vorhergehenden Arbeiten der Arbeitsgruppe BURZLAFF wurde die Entwicklung von verschiedenartigen N,N,O-Liganden für Anwendungen in der Katalyse und in bio- anorganischen Modellkomplexen untersucht. Insbesondere der methylsubstituierte Ligand Bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) besitzt eine vielfältige Chemie, welche viele Parallelen zu den anionischen Cyclopentadienyl- (Cp) und Hydridotris(pyrazol-1- yl)boratoliganden (Tp) aufweist.
Im ersten Teil dieser Arbeit wurde die Darstellung von Tricarbonylmangan(I)komplexen mit dem Heteroskorpionatliganden 3,3-Bis(3,5-dimethylpyrazol-1-yl)propionato (bpzp) und die
Synthese des Trisimidazolylkomplexes [Mn(CO)3(HIm)3]Br (6) untersucht. Diese beiden Komplexe, sowie die analogen Tricarbonylmangankomplexe mit den Hetero- skorpionatliganden Bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza), Bis(pyrazol-1-yl)acetato (bpza) und 3,3-Bis(3,5-dimethylpyrazol-1-yl)propionato (bdmpzp), und der Komplex
[Mn(CO)3(HIm)3]Br, wurden auf ihre Eigenschaften als photoaktivierbare Kohlenstoff- monoxid-freisetzende Moleküle hin untersucht. Hierzu wurde das Myoglobin-Assay verwendet, mit dessen Hilfe gezeigt werden konnte, dass die beiden Komplexe mit den monodentaten Imidazolyl- und Pyrazolylliganden eine geringe Stabilität in Lösung aufweisen und bereits im Dunklen Kohlenstoffmonoxid freisetzen. Für die vier Hetero- skorpionatkomplexe ließ sich eine starke Abhängigkeit der Freisetzungsgeschwindigkeit von dem Substitutionsmuster der Heterozyklen und der Kettenlänge der Carboxylateinheit erkennen.
Der zweite Teil dieser Arbeit beinhaltet die Synthese und Charakterisierung von
Rutheniumcarbonylkomplexen und wurde in Zusammenarbeit mit S. TAMPIER und G.
TÜRKOGLU bearbeitet. Die Synthese der beiden Dicarbonylkomplexe [Ru(bdmpza)Cl(CO)2]
(9) und [Ru(2,2-bdmpzp)Cl(CO)2] (10) !mit einem Bis(3,5-dimethylpyrazol-1-yl)acetato- (bdmpza) oder einem 2,2-!Bis(3,5-dimethylpyrazol-1-yl)propionatoligand (2,2-bdmpzp) wurden bereits von S. TAMPIER und G. TÜRKOGLU beschrieben. In Analogie wurde der auf dem Bis(pyrazol-1-yl)acetatoligand (bpza) basierende Komplex [Ru(bpza)Cl(CO)2] dargestellt. Alle drei Komplexe sind durch die Reaktion des Polymers [RuCl2(CO)2]n mit dem Kaliumsalz des jeweiligen Heteroskorpionatliganden (K[bdmpza], K[bpza] oder K[2,2- bdmpzp]) zugänglich. Die Reaktion der freien Säure Hbdmpza mit [Ru3(CO)12] führte zu der
Bildung von zwei Strukturisomeren des Hydridokomplexes [Ru!(bdmpza)H(CO)2] (11A/11B).
Unter aeroben Bedingungen scheint die Umsetzung von ! [Ru(bdmpza)H(CO)2] (11A/11B) zu 5 dem Ru(I)-Dimer [Ru(bdmpza)!(CO)(μ2-CO)]2 (12) im Vergleich zu dem η -C5H5-Analogon
154 ! ! Zusammenfassung und Ausblick ! !
(Cp) gehindert zu sein. Dimer 12 konnte hingegen durch die Reaktion von Hbdmpza mit catena-[Ru(OAc)(CO)2]n erhalten werden.
Der dritte Abschnitt behandelt einen bioanorganischen Themenbereich und beinhaltet zwei
Rutheniumkomplexe mit Aminophenolliganden. Die Reaktion von [Ru(bdmpza)Cl(PPh3)2] mit Aminophenol (APH) und 2-Amino-4,6-di-tert-butylphenol (tBuAPH) führte zu den zugehörigen Komplexen [Ru(bdmpza)Cl(ISQ)(PPh3)] bzw. [Ru(bdmpza)Cl(IBQ)(PPh3)] (16) tBu tBu und [Ru(bdmpza)Cl( ISQ)(PPh3)] bzw. [Ru(bdmpza)Cl( IBQ)(PPh3)] (15). In beiden Komplexen konnte die ungewöhnliche κ1-Koordination durch die Iminofunktion beobachtet werden und nicht die erwartete κ2-N,O-Koordination. Aus den beobachteten Bindungslängen in den Röntgenstrukturanalysen und den diamagnetischen NMR-Spektren konnte geschluss- folgert werden, dass es sich bei den beiden Komplexen um ein [Ru2+–IBQ]-System oder ein [Ru3+–ISQ]-System mit starker antiferromagnetischer Kopplung handelt. Weitere Arbeiten müssen in Zukunft zeigen welche Redoxprozesse im Detail während der Bildung der Komplexe ablaufen und ob infolgedessen eine Optimierung der Reaktion möglich ist.
Me Me Me Me N N N N O O N O N N O N Me Ru Me oder Me Ru Me NH NH O O Ph3P Cl Ph3P Cl
R R R R 15 (IBQ); R = tBu 15 (ISQ); R = tBu 16 (IBQ); R = H 16 (ISQ); R = H
Der Hauptfokus dieser Arbeit liegt auf einer Serie von kohlenstoffreichen Rutheniumallenylidenkomplexen, die ausgehend von dem Rutheniumprecursor [Ru(bdmpza)-
Cl(PPh3)2] (14) dargestellt wurden. Die Umsetzung von 14 mit 1,1-Bis-(3,5-di-tert- butylphenyl)-1-methoxy-2-propin führte zu der Bildung von zwei Strukturisomeren des
t Allenylidenkomplexes [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19A/19B) und den durch
Zersetzung entstehenden Carbonylkomplex [Ru(bdmpza)Cl(CO)(PPh3)] (18A/18B). Die analoge Umsetzung von 9-Ethinyl-9-fluorenol mit 14 führte zu dem analogen fluorensubstituierten Allenylidenkomplex [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B) (FN = Fluorenyl). Ausgehend von Anthrachinon wurde die Synthese von 10-Ethinyl-10-
155 ! ! Zusammenfassung und Ausblick ! ! hydroxyanthracen-9-on über den TMS-geschützten (TMS = Trimethylsilyl) Propargylalkohol beschrieben. Anschließend erfolgte die Synthese des Allenylidenkomplexes ([Ru(bdmpza)-
Cl(═C═C═(AO))(PPh3)] (25A/25B) (AO = Anthron), der im Falle beider Strukturisomere im Festkörper starke π-π-Wechselwirkungen zwischen zwei Anthroneinheiten aufweist. Im nächsten Schritt wurde in Kooperation mit A. WATERLOO aus der Arbeitsgruppe von R.
TYKWINSKI die Synthese eines größeren acenbasierten, in diesem Fall pentacenchinonbasierten, Allenylidenkomplexes [Ru(bdmpza)Cl-(═C═C═(PCO))(PPh3)] (29A/29B) (PCO = Pentacenon) erzielt. Im Gegensatz zu anderen
Rutheniumallenylidenkomplexen zeigte 29B eine stark gewinkelte Ru–C3-Kette. Diese Geometrie konnte auf das Packungsmotiv im Festkörper zurückgeführt werden, da dieses Verhalten für 29A nicht beobachtet wurde.
tBu tBu
tBu tBu 20A/20B 19A/19B Me Me N N O N O N Me Ru Me
C CR2 = Ph3P Cl CR2 O O 25A/25B 29A/29B
H CN CN
NC CN 31 37A/37B Da erneut nur eine Dimerbildung, aber keine Schichtstruktur der aromatischen Einheiten, im Festkörper vorlag, wurde entschieden, ein weiteres polyaromatisches Keton als Ausgangsverbindung zu wählen. Hierbei wurde 7H-Benzo[no]tetraphen-7-on (34) als vielversprechender Kandidat verwendet, da dieser ein erweitertes π-System auf der dem Keton abgewandten Seite besitzt. Ausgehend von 34 wurde die Synthese des
156 ! ! Zusammenfassung und Ausblick ! !
Propargylalkohols 7-Ethinyl-7H-benzo[no]tetraphen-7-ol (36) und die anschließende
Umsetzung zu dem Allenylidenkomplex [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B) (BT = Benzotetraphen) beschrieben. Hervorzuheben ist Komplex 37A, da eine Reihe an kurzen π-π-Abständen zwischen den Benzotetrapheneinheiten entlang einer Achse im Kristall auftritt, die möglicherweise einen Ladungstransport entlang dieser Achse erlauben könnte. Studien der Absorptionsspektren der bisher erwähnten Komplexe zeigten, dass schwache Banden im NIR-Bereich zu verbotenen MLCT-Übergängen gehören. TD-DFT Berechnungen wurden von E. HÜBNER ausgehend von Röntgenstrukturanalysen durchgeführt. Diese Berechnungen erlauben die Zuordnung dieser NIR-Banden, die durch Absorptionsspektroskopie beobachtet wurden, zu Übergängen, die vor allem HOMO–2, HOMO–1, HOMO und LUMO betreffen. Des Weiteren wurden cyclovoltammetrische Messungen durchgeführt um ein Verständnis für den Einfluss der Substituenten auf den Allenylidenkomplex zu erhalten. Zusammenfassend lässt sich sagen, dass die räumliche Anordnung, die für einige Komplexe im Festkörper beobachtet wurde, diese zu vielversprechenden Kandidaten für Metall-beeinflusste Feldeffekttransistoren macht. Darüber hinaus könnte das reversible Redoxverhalten und das breite Absorptionsverhalten sie zu guten Ausgangsverbindungen für Farbstoffsolarzellen machen. Diese beiden möglichen Anwendungsbeispiele machen diese Komplexe zu interessanten Ausgangsverbindungen für weitere funktionalisierte organische Halbleiter. Der Versuch, einen Allenylidenkomplex ausgehend von 2-(13-(Dicyanomethyl)-13-ethinylpentacen-6(13H)-yliden)malononitril (30) zu erhalten, führte zu dem Rutheniumvinylidenkomplex [Ru(bdmpza)Cl(═C═CH(PCN))-
(PPh3)] (PCN = Pentacenonbasiertes Tetracyanoderivat) (31). Charakteristisch ist die Farbintensität der Verbindung in Lösung, welche stark an Allenylidenkomplexe erinnert und sich vermutlich auf den starken Push-Pull-Charakter der Cyanosubstituenten in Verbindung mit der Vinylideneinheit zurückführen lässt. Für Vergleichszwecke und mögliche katalytische
Anwendungen wurden die 16-VE-Rutheniumallenylidenkomplexe [RuCl2(═C═C═(FN))-
(PPh3)2] (45), [RuCl2(═C═C═(AO))(PPh3)2] (46) und [RuCl2(═C═C═(PCO))(PPh3)2] (47) dargestellt. Jedoch zeigen diese drei Komplexe in Lösung die Tendenz zu dimerisieren und eine Mischung aus einem neutralen und kationischen 18-VE-Komplex zu bilden, was diese für weitere Anwendungen unattraktiv macht.
Die Arbeit befasst sich im anschließenden Kapitel mit Rutheniumkumulenylidenkomplexen, die eine Exfoliation von beispielsweise Kohlenstoffnanoröhren oder Graphenmonolagen erlauben soll. Hierzu wurden zunächst die beiden Rutheniumvinylidenkomplexe
157 ! ! Zusammenfassung und Ausblick ! !
[Ru(bdmpza)Cl(═C═CH(6-Methoxynaphthalen))(PPh3)] (48) und [Ru(bdmpza)Cl-
(═C═CH(Pyr))(PPh3)] (49) dargestellt. Obwohl Komplexe 48 und 49 bemerkenswerte Stabilität für Vinylidenkomplexe zeigen, erfolgt eine Zersetzung durch Sauerstoff in Lösung innerhalb weniger Tage.
Me Me Me Me Me Me N N N N N N O O O N O N N O N N O N Me Ru Me Me Ru Me Me Ru Me PPh Cl C PTA Cl C PTA Cl C 3 C C C C C C
54A 57A 58A
Um diesen Nachteil zu umgehen, sollte im Folgenden die Synthese von pyrenbasierten Allenylidenkomplexen untersucht werden. Hierzu wurde zunächst, ausgehend von Pyrenophenon, (50) der Propargylalkohol 1-Phenyl-1-(pyren-1-yl)prop-2-in-1-ol (51) dargestellt. Der zugehörige Allenylidenkomplex [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B) wurde isoliert und zeigt Absorptionsspektren ähnlich derer des phenylbasierten
Allenylidenkomplexes [Ru(bdmpza)Cl(═C═C═CPh2)(PPh3)]. Dies verdeutlicht, dass keine Konjugation zwischen dem Pyrensubstituenten und der Allenylideneinheit erfolgt. Um die
Löslichkeit in polaren, protischen Lösungsmitteln zu steigern, wurde der Austausch des PPh3- Liganden durch den PTA-Liganden untersucht. Zwar waren die Allenylidenkomplexe [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A) und [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)]
(58A), ausgehend von [Ru(bdmpza)Cl(PTA)(PPh3)] (55), in sehr schlechter Ausbeute darstellbar, jedoch zeigten beide Komplexe 57A und 58A eine schnelle Zersetzung in Lösung. In zukünftigen Arbeiten sollten daher Untersuchungen zu möglichen nicht-kovalenten Funktionalisierungen von Kohlenstoffallotropen, insbesondere mit dem Komplex 54A/54B, durchgeführt werden.
Im letzten Kapitel dieser Arbeit wurde die intramolekulare Scholl-Reaktion von Pyrenophenon (50) detailliert betrachtet. Im Gegensatz zu den bisherigen Veröffentlichungen konnte das Reaktionsprodukt durch eine Röntgenstrukturanalyse als 11H-indeno[2,1-a]pyren-
158 ! ! Zusammenfassung und Ausblick ! !
11-on (64) identifiziert werden. Zusätzlich konnte ein mögliches Intermediat in Form des reduzierten 6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-on (63) isoliert werden. Derzeit werden
Berechnungen von C. WICK aus der Arbeitsgruppe von T. CLARK durchgeführt, die zur Aufklärung des Mechanismus beitragen sollen, da sowohl der Arenium-Kationen Mechanismus als auch ein radikalischer Mechanismus denkbar ist.
O O O
∗ C 50 H2 64 63
159
160
7 EXPERIMENTAL SECTION
161 ! ! Experimental Section ! !
7.1 General Remarks
Working Techniques All air sensitive compounds were prepared under dry nitrogen atmosphere using conventional
Schlenk techniques. Purchased solvents (p.a. grade, <50 ppm H2O) were degassed prior to use and stored under N2 atmosphere.
7.1.1 Chemicals!
The following chemicals were used as purchased without further purification:
" [Mn2(CO)10]
" [Ru3(CO)12] " 1-ethynylpyrene " 2-aminophenol " 2-ethynyl-6-methoxynaphthalene " 7H-benzo[no]tetraphen-7-one " 9-ethynyl-9-fluorenol " anthraquinone " bianthrone " ethynylmagnesium bromide " imidazole " KOtBu " n-BuLi " PTA " pyrazole " trimethylsilylacetylene
The group of R. TYKWINSKI provided the following chemicals:
" 1,1-bis-(1,3-di-t-butylphenyl)-1-methoxy-2-propyne 162 ! ! Experimental Section ! !
" 13-ethynyl-13-hydroxypentacen-6-one " 2-(13-(dicyanomethyl)-13-ethynylpentacen-6(13H)-ylidene)malononitrile " 6,13-diethynyl-6,13-dihydropentacene-6,13-diol
The following chemicals were synthesized by literature methods:
[42] " [Mn(bdmpza)(CO)3] [173] " [Mn(bdmpzp)(CO)3] [42] " [Mn(bpza)(CO)3] [367] " [MnBr(CO)5] [193] " [MnBr(HPz)2(CO)3] [168] " [Ru(bdmpza)Cl(PPh3)2] [368] " [Ru(OAc)(CO)2]n [369] " [RuCl2(CO)2]n [370] " [RuCl2(PPh3)3] " 5-ethynyl-10,11-dihydro-5H-dibenzo[a,d][7]annulen-5-ol[371] " 5-ethynyl-5H-dibenzo[a,d][7]annulen-5-ol " Hbdmpza[372] " Hbpza[42] " Hbpzp[173] " Pyrenophenone[346]
7.1.2 Instrumentation
Elemental analyses were determined with a Euro EA 3000 (Euro Vector) and EA 1108 (Carlo Erba) instrument (σ = ± 1% of the measured content). IR spectra were recorded with an
Excalibur FTS-3500 FTIR in CaF2 cuvettes (0.2 mm) or as KBr pellets. KBr pellets were prepared using a Perkin-Elmer hydraulic press (10 t cm–2). 1H, 13C, APT 13C and 31P NMR spectra were measured with a Bruker Avance DRX400 WB and a Bruker Avance DPX300 NB instrument. The δ values are given relative to tetramethylsilane (1H), the deuterated
13 solvent ( C) or to H3PO4 as internal standard. ESI-MS spectra were recorded with a Bruker
163 ! ! Experimental Section ! !
Daltonics maXis ultrahigh resolution ESI-TOF MS. Peaks were identified by using simulated isotopic patterns created within the Bruker Data Analysis software. X-ray structure determinations were carried out with a Bruker-Nonius Kappa-CCD diffractometer or an Agilent Technologies SuperNova dual source diffractometer. UV/Vis and NIR spectroscopy was performed with a Shimadzu UV-2401PC, a Varian Cary 5000 or a Varian Cary 5G spectrometer.
7.1.3 CO-Release Studies
In a 1 cm quartz cuvette, horse skeletal muscle myoglobin (Sigma-Aldrich) dissolved in 0.1 M phosphate buffer (pH 7.4) and phosphate buffer were mixed to a volume of 890 µL and a final concentration of myoglobin of 50 µM. The mixture was degassed by bubbling N2 through the solution. While still bubbling with N2, 0.1 M sodium dithionite (100 µL) in the same solvent and each complex (10 µL of a 1000 µM DMSO stock solution) were added. The solution was then either kept in the dark for 6 h or irradiated under N2 with a UV hand lamp (Benda 8W) at 365 nm, positioned perpendicular to the cuvette at a distance of 3 cm. Irradiations were interrupted in regular intervals to take UV/Vis spectra on a Cary 5 spectrophotometer. The irradiation experiments were carried out in triplicate.[196-197]
7.1.4 Cyclic Voltammetry
Cyclic voltammetry experiments were done using a AUTOLAB PGSTAT 100. A three- electrode cell was used, using a gold disk working electrode, a platinum wire counter electrode and a silver wire as a pseudo-reference electrode. Cyclic voltammetry was performed in MeCN or CH2Cl2 solution (1.00 mM complex) containing 0.1 M n-Bu4NPF6 as supporting electrolyte. All solutions were deoxygenated with N2 before each experiment and a blanket of N2 was used to cover the solution during the experiment. The potential values (E) were calculated using the following equation: E = (Epc + Epa)/2, where Epc and Epa correspond to the cathodic and anodic peak potentials, respectively. Potentials are referenced to the ferrocenium/ferrocene (Fc+/Fc) couple used as an internal standard.[373]
164 ! ! Experimental Section ! !
7.2 Synthesis of Compounds
7.2.1 Manganese Based Photo-CORMs
7.2.1.1 [Mn(bpzp)(CO)3] (4)
To a solution of Hbpzp (299 mg, 1.45 mmol) in THF (50 mL) KOtBu (163 mg, 1.45 mmol) was added. The reaction mixture was stirred at room temperature for 1 h. After addition of
[MnBr(CO)5] (400 mg, 1.45 mmol) the suspension was stirred under reflux for 14 h and the reaction was monitored via IR spectroscopy. The yellow suspension was filtered and the residue was washed with THF (3 × 30 mL), H2O (3 × 30 mL) and Et2O (3 × 10 mL) and dried in vacuo. The crude product (4) was recrystallized from CH2Cl2. Yield 251 mg (0.73 mmol, 50%).
N ON N O N Mn OC CO CO
1 H NMR (300 MHz, DMSO-d6): δ = 8.07 (s, 2H, pz–CH), 7.93 (s, 2H, pz–CH), 7.51 (t, 3 3 JH,H = 7.5 Hz, 1H, CH), 6.51 (vt, 2H, pz–CH), 3.67 (d JH,H = 7.7 Hz, 2H, CH2) ppm; IR (THF): ṽ 2026 (s), 1932 (s), 1915 (s) cm–1; Due to poor solubility no 13C NMR spectrum could be recorded; IR (KBr): ṽ 2028 (s, CO), 1947 (s, CO), 1929 (w, CO), 1914 (s, CO) cm–1;
Elemental analysis calcd (%) for C12H9MnN4O5: C 41.88, H 2.64, N 16.28; found: C 41.72, H 2.53, N 15.65.
7.2.1.2 [Mn(HIm)3(CO)3]Br (6)
To a solution of imidazole (89.0 mg, 1.30 mmol) in CH2Cl2 (35 mL) [MnBr(CO)5] (178 mg, 0.65 mmol) was added and stirred at room temperature for 5 h. The solvent was removed in vacuum, the yellow residue dispersed in THF (20 mL) to remove excess [MnBr(CO)5] and filtered off yielding the yellow complex (6). Yield 87 mg (0.21 mmol, 32%).
165 ! ! Experimental Section ! !
Br HN HN NH N N N Mn OC CO CO
1 2 H NMR (300 MHz, DMSO-d6): δ = 12.97 (s, 3H, NH), 7.83 (s, 3H, C H), 7.37 (s, 3H, CH),
13 2 6.68 (s, 3H, CH) ppm; C NMR (75 MHz, DMSO-d6): δ = 220.3 (CO), 139.4 (C H), 129.6 (CH), 118.6 (CH) ppm; IR (KBr): ṽ 2024 (s, CO), 1907 (s, CO) cm–1; MS (ESI-TOF, MeCN) m/z (%): calcd: 343.0351; found: 343.0455 (100) [M – Br]+; Elemental analysis calcd (%) for C12H12BrMnN6O3: C 34.06, H 2.86, N 19.86; found: C 33.86, H 2.63, N 20.13.
7.2.2 Ruthenium Carbonyl Complexes Bearing Heteroscorpionate Ligands
7.2.2.1 [Ru(bdmpza)H(CO)2] (11A/B)
To a suspension of [Ru3(CO)12] (522 mg, 0.810 mmol) in toluene (50 mL) was added Hbdmpza (811 mg, 3.26 mmol). The suspension was stirred under reflux for 24 h until complete decolorization was achieved. The white residue was filtered off, washed with toluene (2 × 10 mL), and dried in vacuo to yield a mixture of isomers 11A,B in a 1:0.7 ratio. Yield: 887 mg (2.19 mmol, 90%).
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me OC H CO OC CO H A B
1 Data for isomer 11A are as follows. H NMR (CDCl3, 300 MHz): δ = 6.48 (s, 1H, CH), 6.02 (s, 2H, pz–H4, pz–H4´), 2.42 (s, 6H, pz–Me5, pz–Me5´), 2.38 (s, 6H, pz–Me3, pz–Me3´), –13.32
1 4 (s, 1H, Ru–H) ppm; H NMR (CD2Cl2, 300 MHz): δ = 6.42 (s, 1H, CH), 6.04 (s, 2H, pz–H , pz–H4´), 2.42 (s, 6H, pz–Me5, pz–Me5´), 2.37 (s, 6H, pz–Me3, pz–Me3´), –13.09 (s, 1H, Ru– H) ppm.
166 ! ! Experimental Section ! !
1 Data for isomer 11B are as follows. H NMR (CDCl3, 300 MHz): δ = 6.43 (s, 1H, CH), 6.07 (s, 1H, pz–H4´), 6.05 (s, 1H, pz–H4), 2.45 (s, 3H, pz–Me5´), 2.42 (s, 3H, pz–Me5), 2.41 (s, 3H,
3´ 3 1 pz–Me ), 2.38 (s, 3H, pz–Me ), –10.10 (s, 1H, Ru–H) ppm; H NMR (CD2Cl2, 300 MHz): δ 6.39 (s, 1H, CH), 6.09 (s, 1H, pz–H4´), 6.07 (s, 1H, pz–H4), 2.44 (s, 3H, pz–Me5´), 2.42 (s, 3H, pz–Me5), 2.41 (s, 3H, pz–Me3´), 2.40 (s, 3H, pz–Me3), –10.10 (s, 1H, Ru–H) ppm.
Data for both isomers 11A/11B are as follows. IR (KBr): ṽ 3014 (w, CH), 2037 (s, CO), 2002
– –1 (w, Ru–H), 1961 (s, CO), 1664 (s, as-CO2 ), 1560 (w, C═N) cm ; MS (ESI-TOF, MeCN) m/z (%): 407.03 (32) [M + H]+, 812.05 (100) [2 × M + H]+, 835.03 (27) [2 × M + Na]+, 851.01 (13) [2 × M + K]+, 1240.06 (28) [3 × M + Na]+, 1646.08 (22) [4 × M + Na]+, 2050.11 (4)
+ [4 × M + Na] ; Elemental analysis calcd (%) for C14H16N4O4Ru: C 41.48, H 3.98, N 13.82; found: C 41.48, H 3.84, N 14.03.
7.2.2.2 [Ru(bdmpza)(CO)(μ2-CO)]2 (12)
To a suspension of [Ru2(O2CCH3)2(CO)2]n (233 mg, 1.07 mmol) in THF (30 mL) was added Hbdmpza (293 mg, 1.18 mmol). The suspension was heated at reflux for 24 h, forming the dinuclear product [Ru2(bdmpza)(CO)(μ2-CO)]2. The yellow precipitate (12) was filtered off, washed with THF (2 × 20 mL), and dried in vacuo. Yield: 132 mg (0.16 mmol, 30%).
Me
N ON Me Me N O O CO N C Me Ru Ru C Me OC O N O N Me NO Me N
Me
1 4 4´ H NMR (CDCl3, 300 MHz): δ = 6.31 (s, 2H, CH), 6.04 (s, 4H, pz–H , pz–H ), 2.62 (s, 12H, 5 5´ 3 3´ 1 pz–Me , pz–Me ), 2.35 (s, 12H, pz–Me , pz–Me ) ppm; H NMR (CD2Cl2, 300 MHz): δ = 6.35 (s, 2H, CH), 6.15 (s, 4H, pz–H4, pz–H4´), 2.67 (s, 12H, pz–Me5, pz–Me5´), 2.43 (s, 12H, pz–Me3, pz–Me3´) ppm; Due to poor solubility no 13C NMR spectrum could be recorded;
– IR (KBr): ṽ 2930 (w, CH), 1982 (s, CO), 1762 (s, μ2-CO), 1675 (s, as-CO2 ), 1561 (w, C═N) –1 cm ; IR (CHCl3): ṽ 2076 (vw), 2069 (vw), 2010 (vw-sh), 1978 (s, CO), 1950 (w), 1761 (s,
167 ! ! Experimental Section ! !
– –1 μ2-CO), 1673 (s, as-CO2 ), 1602 (vw), 1559 (w, C═N) cm ; MS (ESI-TOF, MeCN) m/z (%): + + + 405.02 (100) [Ru(bdmpza)(CO)2] , 810.05 (4) [M] , 828.06 (42) [M + H2O] , 881.11 (62) + + [M + 4 × H2O] , 899.10 (60) [M + 5 × H2O] ; UV/Vis (CH2Cl2): λmax (log ε) 287.0 (3.88), 342.9 (3.23), 403.0 nm (3.09); Mp.: 282–285 °C dec; Elemental analysis calcd (%) for
C28H30N8O8Ru2: C 41.58, H 3.74, N 13.86; found: C 41.95, H 3.72, N 13.67.
7.2.2.3 [Ru(bpza)Cl(CO)2] (13)
A solution of Hbpza (192 mg, 1.00 mmol) in THF (20 mL) was treated with KOtBu (112 mg,
1.00 mmol) and stirred for 2 h at room temperature. After addition of [RuCl2(CO)2]n (228 mg, 1.00 mmol), the reaction mixture was heated under reflux and controlled by IR spectroscopy on a regular basis. After completion of the reaction (approx. 24 h), the cream white precipitate
(13) was filtered off, washed with H2O (2 × 10 mL) and Et2O (3 × 10 mL) and dried in vacuo. Yield 219 mg (0.57 mmol, 57%).
N N O N O N Ru OC Cl CO
1 3 3´ 3 H NMR (DMSO-d6, 300 MHz): δ = 8.50 (d, JH,H = 2.3 Hz, 1H, pz–H ), 8.46 (d, JH,H = 2.6 3 3 5´ 3 5 Hz, 1H, pz–H ), 8.45 (d, JH,H = 2.8 Hz, 1H, pz–H ), 8.24 (d, JH,H = 2.3 Hz, 1H, pz–H ), 7.64 3 4´ 3 4 (s, 1H, CH), 6.74 (t, JH,H = 2.4 Hz, 1H, pz–H ), 6.69 (t, JH,H = 2.6 Hz, 1H, pz–H ) ppm; 13 – 3´ C NMR (DMSO-d6, 75 MHz): δ = 194.8 (CO), 193.9 (CO), 163.6 (CO2 ), 148.1 (pz–C ), 144.7 (pz–C3), 135.5 (pz–C5´), 134.5 (pz–C5), 109.1 (pz–C4´), 108.7 (pz–C4), 73.2 (CH) ppm; IR (KBr): ṽ 3121 (w, CH), 2996 (w, CH), 2081 (s, CO), 2014 (s, CO), 1768 (vw), 1760 (vw)
– –1 1668 (s, as-CO2 ), 1514 (w, C═N) cm ; MS (ESI-TOF, DMSO) m/z (%): 406.91 (100) [M + Na]+, 789.83 (60) [2 × M + Na]+, 1172.75 (30) [3 × M + Na]+, 1557.67 (80) [4 × M + Na]+, 1942.59 (50) [5 × M + Na]+, 2325.52 (50) [6 × M + Na]+; Elemental analysis
calcd (%) for C10H7ClN4O4Ru: C 31.30, H 1.84, N 14.60; found: C 31.21, H 1.81, N 14.51.
168 ! ! Experimental Section ! !
7.2.3 Ruthenium Heteroscorpionate Complexes with Aminophenol Based Ligands
7.2.3.1 [Ru(bdmpza)Cl(IBQ)(PPh3)] or [Ru(bdmpza)Cl(ISQ)(PPh3)] (16)
2-Aminophenol (164 mg, 1.50 mmol) was dissolved in THF (50 mL) and deprotonated with
t KO Bu (168 mg, 1.50 mmol) for 1h. [Ru(bdmpza)Cl(PPh3)2] (14) (908 mg, 1.00 mmol) was added to the solution and the mixture was stirred for 24 h at room temperature. The solvent was removed in vacuo, the solid residue was dissolved in CH2Cl2 (10 mL) and loaded on a column (silica, length 10 cm, Ø 4 cm) and washed with a mixture of EtOH/n-pentane (1:1 v/v). A dark blue spot could be eluted with CH2Cl2/acetone (1:1 v/v) and a second purple spot could be isolated by changing the solvent to MeOH. Further chromatography steps of the purple fraction did not lead to purified samples for analysis. The blue crude product was again loaded on a column (silica, length 30 cm, Ø 2 cm) and eluted with CH2Cl2/acetone (1:1 v/v).
The solvent was removed in vacuo and the complex was dissolved in CH2Cl2, precipitated by the addition on n-pentane, filtered off and the complex was obtained as a dark blue powder (16). Yield 25.0 mg (0.033 mmol, 2%).
Me Me Me Me N N N N O O N O N N O N Me Ru Me or Me Ru Me NH NH O O Ph3P Cl Ph3P Cl
IBQ ISQ
1 H NMR (CD2Cl2, 300 MHz): δ = 14.77 (s, 1H, NH), 7.36 – 7.14 (m, 19H, PPh3 + Ar–C), 6.63 (s, 1H, CH), 6.07 (s, 1H, pz–H4’), 5.97 (s, 1H, pz–H4), 2.62 (s, 3H, pz–Me5’), 2.54 (s, 3H,
5 3 3´ 13 pz–Me ), 2.10 (s, 3H, pz–Me ), 1.91 (s, 3H, pz–Me ) ppm; C NMR (CD2Cl2, 75 MHz): – 3` 3 δ = 171.3 (C═O), 166.3 (CO2 ), 158.5 (C═NH), 154.4 (pz–C ), 151.8 (pz–C ), 142.6 (pz– 5’ 5 2 1 C ), 141.9 (APH–CH), 141.3 (pz–C ), 134.2 (vd, JC,P = 9.6, o-PPh3), 132.7 (vd, JC,P = 42.9, 4 i-PPh3), 132.4 (APH–CH), 132.1 (APH–CH), 130.9 (APH–CH), 130.0 (vd, JC,P = 2.6, p- 3 4´ 4 PPh3), 128.1 (vd, JC,P = 9.0, m-PPh3), 108.9 (pz–C ), 109.0 (pz–C ), 69.6 (CH), 15.1 (pz– 3´ 3 5´ 5 31 Me ), 13.6 (pz–Me ), 11.5 (pz–Me ), 11.3 (pz–Me ) ppm; P NMR (CD2Cl2, 122 MHz): δ = 32.7 ppm; MS (ESI-TOF, MeCN) m/z (%):753.12 (5) [M]+, 742.15 (100) [M – Cl + Na]+;
169 ! ! Experimental Section ! !
Elemental analysis calcd (%) for C36H35ClN5O3PRu: C 57.41, H 4.68, N 9.30; found: C 56.85, H 4.67, N 9.05.
7.2.4 Carbon-Rich Ruthenium Allenylidene Complexes
t 7.2.4.1 [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19A/19B)
To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (205 mg, 0.22 mmol) in THF (50 mL) 1,1- bis-(1,3-di-t-butylphenyl)-1-methoxy-2-propyne (150 mg, 0.34 mmol) was added. The suspension was stirred for 72 h at room temperature and consequently heated for 4 h under reflux. The solvent of the purple solution was removed in vacuo yielding the crude product.
The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length
15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with
CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation of isomers was achieved on a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1 v/v) yielding a purple isomer 19A (allenylidene trans to pyrazole) that could not be completely separated from the formed carbonyl complex [Ru(bdmpza)Cl(CO)(PPh3)2] and a red isomer 19B (allenylidene trans to carboxylate). 19A (data extracted from spectra containing the carbonyl complex). Yield: 52 mg.
Me Me Me Me N N N N O O N O N N O N Me Ru Me tBu Me Ru Me Ph P Cl C Ph P C Cl 3 C 3 C C tBu tBu C tBu
tBu tBu tBu tBu A B
1 H NMR (CDCl3, 300 MHz): δ = 7.66 (s, 4H, Ar–H), 7.61 (s, 2H, Ar–H), 7.57 (m, 6H, 4´ m-PPh3), 7.16 (m, 3H, p-PPh3), 7.00 (m, 6H, o-PPh3), 6.69 (s, 1H, CH), 5.81 (s, 1H, pz–H ), 5.69 (s, 1H, pz–H4), 2.59 (s, 3H, pz–Me5´), 2.46 (s, 3H, pz–Me5), 2.33 (s, 3H, pz–Me3), 1.35
170 ! ! Experimental Section ! !
3´ 31 (s, 3H, pz–Me ), 1.24 (s, 36H, t-Bu) ppm; P NMR (CDCl3, 122 MHz): δ = 37.6 ppm; IR – –1 (KBr): ṽ 1912 (m, C═C═C), 1672 s (s, as-CO2 ), 1565 (w, C═N) cm ; MS (ESI-TOF, MeCN) m/z (%): 1025.46 (100) [M – Cl]+, 1061.43 (12) [M + H]+.
19B: Yield: 18 mg (0.017 mmol, 5 %).
1 H NMR (CDCl3, 300 MHz): δ = 7.68 (s, 4H, Ar–H), 7.61 (s, 2H, Ar–H), 7.57 (m, 6H, m-
PPh3), 7.57 (m, 6H, m-PPh3), 7.16 (m, 3H, p-PPh3), 7.03 (m, 6H, o-PPh3), 6.71 (s, 1H, CH), 5.83 (s, 1H, pz–H4´), 5.70 (s, 1H, pz–H4), 2.52 (s, 3H, pz–Me5´), 2.47 (s, 3H, pz–Me5), 2.25 (s,
3 3´ 13 3H, pz–Me ), 1.40 (s, 3H, pz–Me ), 1.24 (s, 36H, t-Bu) ppm; C NMR (CDCl3, 75 MHz): 2 – 3´ 3 δ = 314.7 (d, JCP = 18.3 Hz, Cα), 234.6 (Cβ), 165.9 (CO2 ), 155.6 (pz–C ), 154.8 (pz–C ), 5´ 5 152.4 (Cγ), 151.2 (m-Ph–C), 146.3 (i-Ph–C), 141.3 (pz–C ), 139.5 (pz–C ), 134.5 (d, 2 1 JCP = 9.2 Hz, o-PPh3), 133.5 (d, JCP = 46.8 Hz, i-PPh3), 129.3 (p-PPh3), 127.5 (d, 3 4´ 4 JCP = 9.2 Hz, m-PPh3), 123.9 (o-Ph–C), 123.6 (p-Ph–C), 108.4 (pz–C ), 108.3 (pz–C ), 69.7 (CH), 34.9 (Met-Bu), 14.6 (pz–Me3´), 13.9 (pz–Me3), 11.6 (pz–Me5´), 11.1 (pz–Me5) ppm;
31 P NMR (CDCl3, 122 MHz): δ = 34.5 ppm; IR (KBr): ṽ 1907 (m, C═C═C), 1666 (s, as- – –1 + CO2 ), 1559 (m, C═N) cm ; MS (ESI-TOF, MeCN) m/z (%): 1025.46 (100) [M – Cl] , 1061.43 (12) [M + H]+.
7.2.4.2 [Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B)
To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (1.614 g, 1.78 mmol) in THF (50 mL) 9- ethynyl-9-fluorenol (550 mg, 2.67 mmol) was added, stirred for 48 h at room temperature and finally heated to reflux for 6 h. The solvent of the purple solution was removed in vacuo yielding the crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation of isomers was achieved on a second column (silica, length 25 cm, Ø 4 cm) with
CH2Cl2/acetone (1:1 v/v) yielding a purple isomer 20A (allenylidene trans to pyrazole) and a red isomer 20B (allenylidene trans to carboxylate). (Nomenclature of the fluorenyl moiety is according to IUPAC nomenclature.)
171 ! ! Experimental Section ! !
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me Ph P Cl C Ph P C Cl 3 C 3 C C C
A B
20A: Yield: 738 mg (0.88 mmol, 49 %).
1 H NMR (CDCl3, 300 MHz): δ = 7.56 (m, 6H, m-PPh3), 7.46 (m, 3H, p-PPh3), 7.34 (m, 6H, 1 8 4 5 o-PPh3), 7.27 (m, 2H, FN–H & FN–H ), 7.23 (m, 2H, FN–H & FN–H ), 7.00 (m, 2H, FN– H3 & FN–H6), 6.91 (m, 2H, FN–H2 & FN–H7), 6.69 (s, 1H, CH), 6.04 (s, 1H, pz–H4´), 6.00 (s, 1H, pz–H4), 2.57 (s, 3H, pz–Me5´), 2.50 (s, 3H, pz–Me5), 2.45 (s, 3H, pz–Me3), 1.92 (s, 3H,
3´ 13 2 pz–Me ) ppm; C NMR (CDCl3, 75 MHz): δ = 300.6 (d, JC,P = 27.6 Hz, Cα), 236.4 (d, 3 – 3´ 3 4b JC,P = 4.6 Hz, Cβ), 166.6 (CO2 ), 156.1 (pz–C ), 154.6 (pz–C ), 144.1 (FN–C ), 143.9 (FN– C4a), 141.0 (FN–C9), 141.0 (pz–C5´), 139.6 (pz–C5), 136.2 (FN–C8a), 136.2 (FN–C9a), 134.3 (d,
2 1 2 JC,P = 9.6 Hz, o-PPh3), 132.9 (d, JC,P = 47.0 Hz, i-PPh3), 129.8 (p-PPh3), 129.3 (FN–C & 7 3 6 3 1 FN–C ), 129.2 (FN–C & FN–C ), 128.0 (d, JC,P = 10.3 Hz, m-PPh3), 121.7 (FN–C & FN– C8), 121.2 (FN–C4 & FN–C5), 109.4 (pz–C4´), 108.6 (pz–C4), 69.0 (CH), 14.5 (pz–Me3´), 13.6
3 5´ 5 31 (pz–Me ), 11.4 (pz–Me ), 11.2 (pz–Me ) ppm; P NMR (CDCl3, 122 MHz): δ = 34.6 ppm; – Mp.: 230-235 °C (dec.); IR (KBr): ṽ 1910 (m, C═C═C), 1664 (s, as-CO2 ), 1560 (w, C═N) –1 + + cm ; MS (ESI-TOF, MeCN) m/z (%): 755.19 (17) [M – Cl – CO2] , 825.16 (100) [M + H] ;
Elemental analysis calcd. (%) for C45H38ClN4O2PRu: C 64.78, H 4.59, N 6.72; found: C 64.71, H 4.34, N 6.71.
20B: Yield: 228 mg (0.27 mmol, 15 %).
1 H NMR (CDCl3, 300 MHz): δ = 7.64 (m, 6H, m-PPh3), 7.50 (m, 3H, p-PPh3), 7.38 (m, 6H, 1 8 4 5 o-PPh3), 7.24 (m, 2H, FN–H & FN–H ), 7.18 (m, 2H, FN–H & FN–H ), 7.16 (m, 2H, FN– H3 & FN–H6), 6.99 (m, 2H, FN–H2 & FN–H7), 6.75 (s, 1H, CH), 5.90 (s, 1H, pz–H4´), 5.71 (s, 1H, pz–H4), 2.55 (s, 3H, pz–Me5´), 2.51 (s, 3H, pz–Me5), 2.19 (s, 3H, pz–Me3), 1.42 (s, 3H,
3´ 13 2 pz–Me ) ppm; C NMR (CDCl3, 75 MHz): δ = 314.4 (d, JC,P = 19.3 Hz, Cα), 256.2 (Cβ),
172 ! ! Experimental Section ! !
– 3´ 3 4b 4a 9 165.8 (CO2 ), 155.7 (pz–C ), 154.9 (pz–C ), 145.1 (FN–C ), 143.5 (FN–C ), 141.6 (FN–C ), 5´ 5 8a 9a 2 140.0 (pz–C ), 139.9 (pz–C ), 136.5 (FN–C ), 136.5 (FN–C ), 134.5 (d, JC,P = 9.6 Hz, o- 1 2 7 PPh3), 132.5 (d, JC,P = 47.6 Hz, i-PPh3), 129.7 (p-PPh3), 129.7 (FN–C & FN–C ), 129.4 (FN– 3 6 3 1 8 4 C & FN–C ), 127.8 (d, JC,P = 10.2 Hz, m-PPh3), 122.1 (FN–C & FN–C ), 121.1 (FN–C & FN–C5), 108.4(pz–C4´), 108.3 (pz–C4), 69.6 (CH), 14.3 (pz–Me3´), 13.9 (pz–Me3), 11.8 (pz–
5´ 5 31 Me ), 11.2 (pz–Me ) ppm; P NMR (CDCl3, 122 MHz): δ = 30.9 ppm; Mp.: 235-240 °C – –1 (dec.); IR (KBr): ṽ 1903 (m, C═C═C), 1666 (s, as-CO2 ), 1564 (w, C═N) cm ; MS (ESI- + + TOF, MeCN) m/z (%): 755.19 (17) [M – Cl – CO2] , 825.16 (100) [M + H] ; Elemental analysis calcd. (%) for C45H38ClN4O2PRu: C 64.78, H 4.59, N 6.72; found: C 64.89, H 4.28, N 6.71.
7.2.4.3 10-Hydroxy-10-((trimethylsilyl)ethynyl)anthracen-9-one (23)
To a solution of trimethylsilylacetylene (1.39 mL, 0.980 g, 10.0 mmol) in THF (20 mL) cooled to –40 °C n-BuLi (1.6 M in hexanes, 4.90 mL, 7.80 mmol) was added dropwise. The solution was allowed to stir for 30 min before being transferred slowly via cannula into a suspension of anthraquinone (2.09 g, 10.1 mmol) in THF (40 mL) at room temperature. The reaction mixture was stirred for 40 h at room temperature, cooled to 0 °C and quenched via the addition of water (10 mL). The suspension was filtered off, washed with H2O/THF
(2 × 4 mL, H2O:THF = 1:1), pure THF (3 × 10 mL) and saturated aq. NH4Cl (100 mL) was added to the filtrate. The aqueous phase was extracted with CH2Cl2 (3 × 100 mL), dried over
Na2SO4 and the solvent was removed in vacuo to yield a red powder. The crude product was separated from unreacted anthraquinone via column chromatography with CH2Cl2 as eluent (silica, length 15 cm, Ø 4 cm) to obtain 23 as pink solid. Yield 2.74 g (8.95 mmol, 89 %).
Si
OH
O
173 ! ! Experimental Section ! !
1 3 H NMR (300 MHz, CDCl3): δ = 8.17 (m, 2H, AO-H), 8.08 (d, JH,H = 7.7 Hz, 2H, AO-H),
7.71 (m, 2H, AO-H), 7.51 (m, 2H, AO-H), 3.16 (s, 1H, OH), 0.16 (s, 9H, Si(CH3)3) ppm; 13 C NMR (75 MHz, CDCl3): δ = 183.1 (C=O), 143.7, 134.3, 129.4, 129.2, 128.4, 127.3,
106.7 (Calkyne-Si), 91.5 (Calkyne), 66.4 (C-OH), –0.2 (Si(CH3)3) ppm; IR (KBr): ṽ 3072 (w, CH), 2957 (w, CH), 2899 (w, CH), 2172 (w, C≡C), 1649 (vs, CO), 1599 (s), 1582 (s), 1456 (m) cm–1; MS (ESI-TOF, MeCN) m/z (%): 305.10 (100) [M – H]–; Elemental analysis calcd
(%) for C19H18O2Si: C 74.47, H 5.92; found: C 74.64, H 5.91.
7.2.4.4 10-Ethynyl-10-hydroxyanthracen-9-one (24)
To a solution of the TMS protected propargyl alcohol 23 (1.00 g, 3.26 mmol) in MeOH
(20 mL) a solution of KOH (5.00 mL, 4.00 M in H2O) was added. The resulting mixture was stirred for 2 h under ambient conditions. The solvent was removed in vacuo, the crude product was extracted with CH2Cl2 (5 × 100 mL), washed with H2O (3 × 100 mL), dried over
Na2SO4 and the solvent was removed in vacuo to obtain a grey powder (24). Yield 649 mg (2.77 mmol, 85 %).
H
OH
O
1 3 H NMR (300 MHz, CDCl3): δ = 8.26 (m, 2H, AO-H), 8.11 (d, JH,H = 7.9 Hz, 2H, AO-H), 7.74 (m, 2H, AO-H), 7.55 (m, 2H, AO-H), 2.98 (s, 1H, OH), 2.71 (s, 1H, CH) ppm; 1H NMR
(300 MHz, DMSO-d6): δ = 8.09 (m, 4H, AO-H), 7.83 (m, 2H, AO-H), 7.60 (m, 2H, AO-H),
13 7.15 (s, 1H, OH), 3.70 (s, 1H, CH) ppm; C NMR (75 MHz, DMSO-d6): δ = 182.4 (C=O),
145.1, 134.3 (2 × CH), 128.9 (CH), 128.4, 128.4 (2 × CH), 126.2 (CH), 87.1 (Calkyne), 76.1
(Calkyne-H), 64.2 (C-OH) ppm; IR (KBr): ṽ 3256 (m, OH), 2956 (s, CH), 2918 (vs, CH), 2849 (s, CH), 2112 (w, C≡C), 1772 (m, CO), 1733 (m), 1656 (m) cm–1; MS (ESI-TOF, MeCN) m/z
– (%): 233.06 (19) [M – H] ; Elemental analysis calcd (%) for C16H10O2: C 82.04, H 4.30; found: C 82.36, H 4.30.
174 ! ! Experimental Section ! !
7.2.4.5 [Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B)
[Ru(bdmpza)Cl(PPh3)2] (14) (341 mg, 0.400 mmol) and 10-ethynyl-10-hydroxyanthracen-9- one (24) (300 mg, 1.28 mmol) were suspended in THF (80 mL) and stirred at room temperature for 48 h. The solvent of the purple solution was removed in vacuo yielding the crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column
(silica, length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with
CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation of isomers was achieved on a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1 v/v) yielding a purple isomer 25A (allenylidene trans to pyrazole) and a red isomer 25B (allenylidene trans to carboxylate).
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me Ph P Cl C Ph P C Cl 3 C 3 C C O
O A B
25A: Yield: 185 mg (0.215 mmol, 54 %).
1 3 3 H NMR (CDCl3, 300 MHz): δ = 8.18 (d, JH,H = 7.5 Hz, 2H, AO–H), 7.94 (t, JH,H = 7.4 Hz,
2H, AO–H), 7.78 (m, 2H, AO–H), 7.54 (m, 6H, m-PPh3), 7.32 (m, 3H, p-PPh3), 7.25 (m, 6H, 4' 4 o-PPh3), 7.18 (m, 2H, AO–H), 6.77 (s, 1H, CH), 6.08 (s, 1H, pz–H ), 5.98 (s, 1H, pz–H ), 2.60 (s, 3H, pz–Me5'), 2.55 (s, 3H, pz–Me5), 2.21 (s, 3H, pz–Me3), 2.00 (s, 3H, pz–Me3') ppm;
13 2 3 C NMR (CDCl3, 75 MHz): δ = 292.1 (d, JC,P = 26.8 Hz, Cα), 251.0 (d, JC,P = 5.0 Hz, Cβ), – 3' 3 4 187.1 (C=O), 166.3 (CO2 ), 156.3 (pz–C ), 154.7 (pz–C ), 141.4 (d, JC,P = 3.0 Hz, Cγ), 141.1 5' 4 5 3 (pz–C ), 139.8 (d, JC,P = 2.0 Hz, pz–C ), 134.3 (2 × AO–CH), 134.1 (d, JC,P = 6.9 Hz, o- 1 PPh3), 133.3 (d, JC,P = 38.6 Hz, i-PPh3), 132.4 (2 × AO–C), 132.0 (2 × AO–C), 130.0 (d, 4 JC,P = 2.0 Hz, p-PPh3), 128.8 (2 × AO–CH), 128.3 (2 × AO–CH), 128.2 (2 × AO–CH), 128.0 2 4' 4 3' (d, JC,P = 9.9 Hz, o-PPh3), 109.5 (pz–C ), 108.2 (pz–C ), 69.1 (CH), 14.5 (pz–Me ), 13.2 (pz–
175 ! ! Experimental Section ! !
3 5' 5 31 Me ), 11.4 (pz–Me ), 11.1 (pz–Me ) ppm; P NMR (CDCl3, 122 MHz): δ = 30.1 ppm; IR – –1 (CH2Cl2): ṽ 1880 (m, C═C═C), 1666 (s, as-CO2 ), 1592 (m, C═N) cm ; UV/vis (CH2Cl2):
λmax (log(ε)): 363 nm (3.17), 580 nm (3.44); MS (ESI-TOF, MeCN) m/z (%): 783.18 (12) + + + [M – Cl – CO2] , 824.21 (13) [M – Cl – CO2 + MeCN] , 863.14 (100) [M + H] ; Elemental analysis calcd. (%) for C46H38ClN4O3PRu: C 64.07, H 4.44, N 6.50; found: C 63.83, H 4.42, N 6.51.
25B: Yield: 56.0 mg (0.0650 mmol, 16 %).
1 3 3 H NMR (CDCl3, 300 MHz): δ = 8.18 (d, JH,H = 7.5 Hz, 2H, AO–H), 7.98 (t, JH,H = 7.4 Hz, 3 2H, AO–H), 7.77 (d, JH,H = 7.8 Hz, 2H, AO–H), 7.64 (m, 6H, m-PPh3), 7.47 (m, 6H, o-PPh3, 4' 4 2H, AO–H), 7.13 (m, 3H, p-PPh3), 6.84 (s, 1H, CH), 5.89 (s, 1H, pz–H ), 5.74 (s, 1H, pz–H ), 2.60 (s, 3H, pz–Me5'), 2.54 (s, 3H, pz–Me5), 2.06 (s, 3H, pz–Me3), 1.39 (s, 3H, pz–Me3') ppm;
13 2 C NMR (CDCl3, 75 MHz): δ = 309.6 (d, JC,P = 19.8 Hz, Cα), 277.0 (Cβ), 187.8 (C=O), – 3' 3 3 5' 165.9 (CO2 ), 155.4 (pz–C ), 154.7 (d, JC,P = 2.0 Hz, pz–C ), 141.6 (Cγ), 140.5 (pz–C ), 140.1 4 5 1 (d, JC,P = 2.0 Hz, pz–C ), 134.4 (2 × AO–CH), 134.3 (2 × AO–CH), 133.0 (d, JC,P = 35.7 Hz, 3 4 i-PPh3), 132.1 (d, JC,P = 9.9 Hz, o-PPh3), 132.0 (d, JC,P = 3.0 Hz, p-PPh3), 131.9 (2 × AO–C), 2 129.2 (2 × AO–C), 128.0 (d, JC,P = 11.9 Hz, o-PPh3), 127.8 (2 × AO–CH), 127.7 (2 × AO– CH), 108.3 (pz–C4'), 108.3 (pz–C4), 69.6 (CH), 14.0 (pz–Me3'), 13.5 (pz–Me3), 11.7 (pz–Me5'),
5 31 11.2 (pz–Me ) ppm; P NMR (CDCl3, 122 MHz): δ = 29.1 ppm; IR (CH2Cl2): ṽ 1896 (m, – –1 C═C═C), 1667 (s, as-CO2 ), 1605 (w, C═N) cm ; MS (ESI-TOF, MeCN) m/z (%): 412.11 2+ + (62) [M – Cl – CO2 + MeCN] , 687.11 (31) [Ru(bdmpza)Cl(PPh3)(MeCN)] , 783.18 (88) + + + [M – Cl – CO2] , 824.21 (100) [M – Cl – CO2 + MeCN] , 863.14 (4) [M + H] ; Elemental analysis calcd. (%) for C46H38ClN4O3PRu: C 64.07, H 4.44, N 6.50; found: C 63.38, H 4.41, N 6.40.
7.2.4.6 [Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A/29B)
A suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (101 mg, 0.111 mmol) and 13-ethynyl-13- hydroxypentacen-6-one (28) (60 mg, 0.17 mmol) in THF (25 mL) was stirred at room temperature for 4 d and the reaction was monitored by IR spectroscopy. The solvent was removed in vacuo and the residue was loaded with CH2Cl2 on a column (silica, length 10 cm,
Ø 4 cm). The column was washed with n-pentane/Et2O (1:1, v/v) and eluted with
176 ! ! Experimental Section ! !
CH2Cl2/acetone/n-hexane (1:1:1, v/v). Separation of the main isomer from a mixture of both isomers was achieved by an additional column chromatographic step (CH2Cl2/acetone/n- hexane, 1:1:1, v/v/v) on a longer column (silica, length 35 cm, Ø 6 cm). The fractions were evaporated, redissolved in CH2Cl2 (2 mL) and precipitated by the addition of n-pentane (50 mL).
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me Ph P Cl C Ph P C Cl 3 C 3 C C C O
O A B
29A: Yield 20 mg (0.021 mmol, 19%).
1 H NMR (CD2Cl2, 300 MHz): δ = 8.80 (s, 2H, PCO–H), 8.47 (s, 2H, PCO–H), 8.01 (d, 3 3 JH,H = 8.1 Hz, 1H, PCO–H), 7.80 (app. t, JH,H = 7.1 Hz, 2H, PCO–H), 7.73 – 7.70 (m, 5H, 3 Ar–H), 7.62 (app. t, JH,H = 8.7 Hz, 2H, PCO–H), 7.50 – 7.40 (m, 5H, Ar–H), 7.35 – 7.29 (m, 2H, Ar–H), 7.25 – 7.21 (m, 6H, Ar–H), 6.81 (s, 1H, CH), 6.13 (s, 1H, pz–H4´), 6.10 (s, 1H, pz–H4), 2.63 (s, 3H, pz–Me5´), 2.59 (s, 3H, pz–Me5), 2.29 (s, 3H, pz–Me3), 2.01 (s, 3H, pz–
3´ 13 2 Me ) ppm; C NMR (75 MHz, CD2Cl2): δ = 302.0 (d, JC,P = 19.3 Hz, Cα), 255.6 (Cβ), 186.0
– 3´ 3 5´ 5 (C=O), 166.2 (CO2 ), 156.2 (pz–C ), 154.9 (pz–C ), 142.5 (pz–C ), 140.9 (pz–C ), 139.4 2 1 (Cγ), 137.4 (PCO–C), 134.7 (d, JC,P = 8.7 Hz, o-PPh3), 133.3 (d, JC,P = 41.8 Hz, i-PPh3) 132.9
(PCO–C), 132.2 (p-PPh3), 131.0 (PCO–CH), 131.0 (PCO–CH), 129.8 (PCO–CH), 128.8 (d, 2 JC,P = 12.3 Hz, m-PPh3), 128.2 (PCO–CH), 128.1 (PCO–CH), 127.9 (PCO–CH), 108.8 (pz– C4´), 108.6 (pz–C4), 69.9 (CH), 14.5 (pz–Me3´), 13.7 (pz–Me3), 11.9 (pz–Me5´), 11.3 (pz–Me5)
31 ppm; P NMR (122 MHz, CD2Cl2): δ = 33.1 ppm; IR (CH2Cl2): ṽ 1916 (m, C═C═C), 1663 – –1 (s, as-CO2 ), 1564 (m, C═N) cm ; MS (ESI-TOF, CH2Cl2) m/z (%): 742.12 (100) + [M + H + MeCN – PPh3] ; Elemental analysis calcd (%) for
C54H42ClN4O3PRu × 1.25 CH2Cl2: C 62.10, H 4.20, N 5.24; found C 62.11, H 4.19, N 5.23.
177 ! ! Experimental Section ! !
29B: Yield of 29A/29B: 46 mg (0.048 mmol, 43%).
The most prominent signals of compound 29B could be extracted from the combined spectra.
Due to the strong contamination with 29A the signals for Cα and Cβ could not be observed. 1 H NMR (300 MHz, CD2Cl2): δ = 8.81 (s, 2H, PCO–H), 8.59 (s, 2H, PCO–H), 6.85 (s, 1H, CH), 5.95 (s, 1H, pz–H4´), 5.79 (s, 1H, pz–H4), 2.63 (s, 3H, pz–Me5´), 2.59 (s, 3H, pz–Me5),
3 3´ 13 2.21 (s, 3H, pz–Me ), 1.52 (s, 3H, pz–Me ) ppm; C NMR (75 MHz, CD2Cl2): δ = 185.6 – 3´ 3 5´ (C=O), 166.6 (CO2 ), 156.4 (pz–C ), 154.8 (pz–C ), 142.0 (pz–C ), 140.4 (Cγ), 140.3 (pz– 5 2 C ), 137.4 (PCO–C), 134.4 (d, JC,P = 9.6 Hz, o-PPh3), 132.9 (PCO–C), 132.6 (d, 1 JC,P = 36.6 Hz, i-PPh3), 132.3 (p-PPh3), 131.3 (PCO–CH), 130.3 (PCO–CH), 130.2 (PCO– 2 CH), 128.3 (d, JC,P = 15.7 Hz, m-PPh3), 128.2 (PCO–CH), 128.1 (PCO–CH), 127.8 (PCO– CH), 108.6 (pz–C4´), 108.5 (pz–C4), 69.5 (CH), 14.8 (pz–Me3´), 13.4 (pz–Me3), 11.6 (pz–
5´ 5 31 Me ), 11.4 (pz–Me ) ppm; P NMR (122 MHz, CD2Cl2): δ = 27.4 ppm; IR (CH2Cl2): ṽ 1916 – –1 (m, C═C═C), 1663 (s, as-CO2 ), 1564 (w, C═N) cm .
7.2.4.7 [Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31)
To a solution of 2-(13-(dicyanomethyl)-13-ethynylpentacen-6(13H)-ylidene)malononitrile
(50 mg, 0.12 mmol) in THF (20 mL) [Ru(bdmpza)Cl(PPh3)2] (14) (91 mg, 0.10 mmol) was added. The yellow suspension turned immediately dark brown and within 30 min dark blue. The solution was stirred for 16 h at room temperature and the solvent removed in vacuo. The isolation of the complex was achieved via column chromatography under N2 atmosphere. The crude dark blue product was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with
CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation from further residues was achieved on a second column (silica, length 25 cm, Ø 4 cm) with
CH2Cl2/acetone (1:1 v/v) yielding a blue complex 31 (vinylidene trans to pyrazole). Yield: 43.0 mg (0.040 mmol, 30 %).
178 ! ! Experimental Section ! !
Me Me N N O N O N Me Ru Me Ph P Cl C CN 3 CH CN
NC CN
1 3 H NMR (300 MHz, CDCl3): δ = 8.68 (s, 2H, PCN–H), 8.47 (d, JH,H = 8.5 Hz, 2H, PCN–H),
8.02 (m, 4H, PCN–H), 7.65 (m, 13H, o-PPh3, p-PPh3, PCN–H), 7.40 (m, 6H, m-PPh3), 6.48 (s, 4´ 4 1H, CH), 5.93 (s, 1H, pz–H ), 4.98 (s, 1H, pz–H ), 3.82 (s, 1H, Hß), 3.47 (s, 1H, HC(CN)2), 2.51 (s, 3H, pz–Me5´), 2.15 (s, 3H, pz–Me5), 1.94 (s, 3H, pz–Me3), 1.91 (s, 3H, pz–Me3´) ppm;
13 2 – 3´ C NMR (75 MHz, CDCl3): δ = 365.1 (d, JC,P = 39.1 Hz, Cα), 167.6 (CO2 ), 157.1 (pz–C ),
3 3 5´ 5 156.9 (C═C(CN)2), 155.6 (d, JC,P = 2.9 Hz, pz–C ), 140.7 (pz–C ), 138.5 (pz–C ), 134.6 2 1 (PCN–CH), 134.1 (d, JC,P = 9.5 Hz, o-PPh3), 133.7 (PCN–C), 133.3 (d, JC,P = 42.2 Hz, i-
PPh3), 132.7 (PCN–C), 132.5 (PCN–C), 129.8 (PCN–CH), 129.7 (p-PPh3), 129.6 (PCN–CH), 129.5 (PCN–CH), 129.3 (PCN–CH), 129.1 (PCN–CH), 129.1 (PCN–CH), 128.9 (PCN–CH),
3 128.7 (PCN–CH), 128.5 (PCN–CH), 128.4 (PCN–CH), 128.1 (d, JC,P = 9.6 Hz, m-PPh3), 127.9 (PCN–C), 127.8 (PCN–CH), 127.1 (PCN–C), 126.9 (PCN–C), 119.1 (CN), 113.4 (CN),
4 4 4´ 110.6 (CN), 110.1 (CN), 113.3 (Cß), 109.3 (pz–C ), 106.6 (d, JC,P = 2.9 Hz, pz–C ), 82.5
3´ 3 (C═C(CN)2), 68.0 (CH), 49.9 (Cγ) 39.5 (CH(CN)2), 14.2 (pz–Me ), 12.9 (pz–Me ), 10.4 (pz– Me5´), 10.0 ppm (pz–Me5), 2 tertiary carbon atoms of the pentacenequinone moiety could not
31 be observed; P NMR (122 MHz, CD2Cl2): δ = 44.6 ppm; IR (CHCl3): ṽ 3009 (m), 2198 (m, – –1 C≡N), 2126 (w, C≡N), 1658 (s, as-CO2 ) cm ; MS (ESI-TOF, CH2Cl2) m/z (%): 1077.21 (15) [M + H]+, 1099.20 (100) [M + Na]+, 1115.17 (20) [M + K]+, 2176.40 (30) [2 × M + Na]+;
7.2.4.8 7-((Trimethylsilyl)ethynyl)-7H-benzo[no]tetraphen-7-ol (35)
To a solution of trimethylsilylacetylene (99.0 µL, 68.3 mg, 0.713 mmol) in THF (20 mL) cooled to –80 °C n-BuLi (1.6 M in hexanes, 401 µL, 0.642 mmol) was added dropwise. The solution was allowed to stir for 30 min before being transferred slowly via cannula into a solution of 7H-benzo[no]tetraphen-7-one (34) (50.0 mg, 0.178 mmol) in THF (20 mL) at room temperature. The reaction mixture was stirred for 16 h at room temperature. The 179 ! ! Experimental Section ! ! reaction was cooled to 0 °C and quenched via the addition of water (3 mL). The solvent was removed in vacuo, the crude product was dissolved in CH2Cl2 and dried over Na2SO4 to yield 35 as yellow powder. Yield 66.0 mg (0.17 mmol, 98%).
Si
OH
1 3 H NMR (300 MHz, CDCl3): δ = 8.70 (m, 1H), 8.38 (d, JH,H = 7.4 Hz, 1H), 8.30 (m, 2H),
7.94 (m, 4H), 7.68 (m, 2H), 7.54 (m, 2H), 2.59 (s, 1H, OH), 0.23 (s, 9H, Si(CH3)3) ppm; 13 C NMR (75 MHz, CDCl3): δ = 135.6 (C), 135.6 (C), 135.1 (C), 133.4 (C), 130.2 (C), 129.1 (CH), 128.8 (CH), 128.7 (CH), 128.7 (C), 128.3 (CH), 127.8 (C), 127.7 (CH), 127.5 (CH),
126.7 (CH), 126.6 (CH), 126.5 (CH), 126.2 (CH), 126.0 (CH), 125.7 (CH), 107.6 (Calkyne-Si),
93.2 (Calkyne), 69.9 (C–OH), 0.01 (Si(CH3)3) ppm (one tertiary carbon atom not observed); MS (ESI-TOF, MeCN) m/z (%): 413.11 (18) [M + Cl]–.
7.2.4.9 7-Ethynyl-7H-benzo[no]tetraphen-7-ol (36)
To a solution of 35 (66.0 mg, 0.174 mmol) in MeOH (20 mL) a solution of KOH (0.50 mL,
4.00 M in H2O) was added. The resulting mixture was stirred for 3 h under ambient conditions. The solvent was removed in vacuo, the crude product was extracted with CH2Cl2
(50 mL), washed with H2O (3 × 25 mL), dried over Na2SO4 and then the solvent was removed under vacuum to yield 7-ethynyl-7H-benzo[no]tetraphen-7-ol (36) as an orange-brown powder. Yield 37.3 mg (0.12 mmol, 70%).
180 ! ! Experimental Section ! !
H
OH
1 H NMR (300 MHz, CDCl3): δ = 8.67 (m, 1H), 8.29 (m, 3H), 7.91 (m, 4H), 7.67 (m, 2H),
13 7.52 (m, 2H), 2.92 (s, 1H, OH), 2.91 (s, 1H) ppm; C NMR (75.5 MHz, CDCl3): δ = 135.7 (C), 135.3 (C), 135.2 (C), 135.0 (C), 133.3 (C), 130.0 (C), 128.9 (C), 129.0 (CH), 128.9 (CH), 128.6 (CH), 128.3 (CH), 128.3 (CH), 127.5 (CH), 127.4 (CH), 126.6 (CH), 126.5 (CH), 126.2
(CH), 126.2 (C), 125.7 (CH), 125.5 (CH), 86.6 (Calkyne), 76.4 (Calkyne–H), 69.1 (C–OH) ppm; MS (ESI-TOF, MeCN) m/z (%): 289.10 (48) [M – OH]+.
7.2.4.10 [Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B)
[Ru(bdmpza)Cl(PPh3)2] (14) (111 mg, 0.122 mmol) and 7-ethynyl-7H-benzo[no]tetraphen-7- ol (36) (37.3 mg, 0.122 mmol) were suspended in THF (80 mL) and stirred at room temperature for 72 h. The solvent of the deep blue solution was removed in vacuo to yield the crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column
(silica, length 15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with
CH2Cl2/acetone (1:1 v/v) and then the solvent was removed in vacuo. Separation of isomers was achieved on a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1 v/v) yielding a blue isomer 37A (allenylidene trans to pyrazole) and a blue isomer 37B (allenylidene trans to carboxylate).
181 ! ! Experimental Section ! !
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me Ph P Cl C Ph P C Cl 3 C 3 C C C
A B
37A: Yield: 62.6 mg (0.067 mmol, 55%).
1 3 3 H NMR (300 MHz, CD2Cl2): δ = 9.11 (d, JH,H = 7.4 Hz, 1H, BT–H), 8.92 (d, JH,H = 8.5 Hz, 3 3 1H, BT–H), 8.70 (d, JH,H = 7.9 Hz, 1H, BT–H), 8.42 (d, JH,H = 7.9 Hz, 1H, BT–H), 8.13 (d, 3 3 JH,H = 7.4 Hz, 1H, BT–H), 7.98 (d, JH,H = 8.7 Hz, 1H, BT–H), 7.82 (s, 2H, BT–H), 7.57 (m, 3 8H, PPh3 + BT–H), 7.33 (m, 10H, PPh3 + BT–H), 7.13 (t, JH,H = 7.7 Hz, 1H, BT–H), 6.74 (s, 1H, CH), 6.10 (s, 1H, pz–H4´), 6.09 (s, 1H, pz–H4), 2.63 (s, 3H, pz–Me5´), 2.59 (s, 3H, pz–
5 3 3´ 13 Me ), 2.31 (s, 3H, pz–Me ), 1.93 (s, 3H, pz–Me ) ppm; C NMR (75 MHz, CD2Cl2): 2 3 – 3´ δ = 273.6 (d, JC,P = 19.2 Hz, Cα), 221.1 (d, JC,P = 3.5 Hz, Cß), 166.4 (CO2 ), 156.3 (pz–C ), 3 5´ 5 4 154.8 (pz–C ), 141.6 (pz–C ), 140.5 (pz–C ), 139.8 (d, JC,P = 1.7 Hz, Cγ), 139.1 (BT–C), 2 136.2 (BT–C), 134.6 (d, JC,P = 7.0 Hz, o-PPh3), 134.4 (BT–C), 134.2 (BT–C), 133.8 (BT–C), 1 4 132.6 (d, JC,P = 48.9 Hz, i-PPh3), 130.5 (BT–CH), 130.0 (d, JC,P = 2.6 Hz, p-PPh3), 129.8 (BT–C), 129.7 (BT–CH), 129.7 (BT–CH), 129.1 (BT–C), 129.1 (BT–CH), 128.8 (BT–CH),
3 128.7 (BT–CH), 128.1 (d, JC,P =9.7 Hz, m-PPh3), 127.9 (BT–CH), 127.8 (BT–CH), 127.7 (BT–CH), 127.5 (BT–CH), 126.9 (BT–CH), 126.0 (BT–CH), 109.3 (pz–C4´), 108.4 (pz–C4), 69.4 (CH), 14.4 (pz–Me3´), 13.5 (pz–Me3), 11.5 (pz–Me5´), 11.3 (pz–Me5) ppm (one tertiary
31 carbon atom not observed); P NMR (122 MHz, CD2Cl2): δ = 35.2 ppm; IR (KBr): ṽ 1903 – –1 (m, C═C═C), 1661 (s, as-CO2 ), 1560 (m, C═N) cm ; MS (ESI-TOF, MeCN) m/z (%): + + 934.18 (100) [M] , 855.22(23) [M – Cl – CO2] ; Elemental analysis calcd. (%) for
C53H42ClN4O2PRu: C 68.12, H 4.53, N 6.00; calcd. (%) for C53H42ClN4O2PRu × 0.15 CH2Cl2: C 67.43, H 4.50, N 5.92; found: C 67.43, H 4.51, N 5.89.
37B: Yield: 17.1 mg (0.018 mmol, 15%).
182 ! ! Experimental Section ! !
1 3 3 H NMR (300 MHz, CD2Cl2): δ = 9.12 (d, JH,H = 7.5 Hz, 1H, BT–H), 8.93 (d, JH,H = 8.6 Hz, 3 3 1H, BT–H), 8.71 (d, JH,H = 7.9 Hz, 1H, BT–H), 8.44 (d, JH,H = 8.1 Hz, 1H, BT–H), 8.24 (d, 3 3 3 JH,H = 7.5 Hz, 1H, BT–H), 8.03 (d, JH,H = 8.8 Hz, 1H, BT–H), 7.80 (d, JH,H = 3.9 Hz, 2H, 3 BT–H), 7.60 (m, 9H, PPh3 + BT–H), 7.38 (d, JH,H = 8.8 Hz, 1H, BT–H), 7.19 (m, 9H, 4´ 4 PPh3 + BT–H), 6.76 (s, 1H, CH), 5.91 (s, 1H, pz–H ), 5.74 (s, 1H, pz–H ), 2.59 (s, 3H, pz– Me5´), 2.55 (s, 3H, pz–Me5), 2.20 (s, 3H, pz–Me3), 1.40 (s, 3H, pz–Me3´) ppm; 13C NMR
2 – (75 MHz, CD2Cl2): δ = 289.5 (d, JC,P = 18.4 Hz, Cα), 237.2 (Cß), 166.4 (CO2 ), 156.2 (pz– 3´ 3 5´ 5 C ), 154.8 (pz–C ), 142.4 (pz–C ), 140.5 (pz–C ), 138.9 (BT–C), 138.3 (BT–C), 138.0 (Cγ), 1 2 135.4 (d, JC,P = 46.0 Hz, i-PPh3), 134.7 (d, JC,P = 9.2 Hz, o-PPh3), 134.2 (BT–C), 133.6 (BT– C), 132.4 (BT–C), 132.2 (BT–CH), 132.0 (BT–C), 131.4 (BT–CH), 130.8 (BT–CH), 130.6
4 (BT–C), 130.2 (BT–CH), 129.8 (d, JC,P = 1.8 Hz, p-PPh3), 129.6 (BT–CH), 129.5 (BT–CH), 3 129.3 (BT–CH), 128.8 (BT–CH), 128.4 (BT–CH), 128.0 (d, JC,P = 9.2 Hz, m-PPh3), 127.8 (BT–CH), 127.6 (BT–CH), 126.5 (BT–CH), 125.3 (BT–C), 108.5 (pz–C4´), 108.3 (pz–C4), 70.0 (CH), 14.4 (pz–Me3´), 13.7 (pz–Me3), 11.9 (pz–Me5´), 11.3 (pz–Me5) ppm; 31P NMR
– (122 MHz, CD2Cl2): δ = 32.3 ppm; IR (KBr): ṽ 1907 (m, C═C═C), 1662 (s, as-CO2 ), 1560 (m, C═N) cm–1; MS (ESI-TOF, MeCN) m/z (%): 934.18 (100) [M]+.
7.2.4.11 Bisanthenequinone (39)
Bisanthenequinone was prepared similar to a route described by T. A. PAVICH et al.[306]
A solution of bianthrone (1.00 g, 2.60 mmol) in benzene (200 mL) was irradiated with a mercury vapor lamp for 8 h under argon without external heating (approx. 40 °C). The resulting brown precipitate (39) was filtered off, washed with benzene (2 × 20 mL) and
CH2Cl2 (3 × 10 mL) and dried in vacuo. Yield 200 mg (0.53 mmol, 20%).
A second crop of bisanthenequinone (39) could be obtained by irradiating the benzene solution under aerobic conditions for 8 h. The resulting orange precipitate was filtered off, washed with benzene (2 × 20 mL) and CH2Cl2 (3 × 10 mL) and dried in vacuo. Yield 360 mg (0.95 mmol, 37 %). Total yield 560 mg (1.47 mmol, 57 %)
183 ! ! Experimental Section ! !
O
O
The compound is highly insoluble in any organic solvent and only allows the recording of a
1 H NMR spectrum in D2SO4.
1 3 3 H NMR (300 MHz, D2SO4): δ = 8.63 (d, JH,H = 8.3 Hz, 4H), 8.22 (d, JH,H = 8.1 Hz, 4H), 3 7.26 (t, JH,H = 7.9 Hz, 4H) ppm; IR (KBr): ṽ 3077 (w, CH), 2920 (w, CH), 2851 (w, CH), 1970 (vw), 1659 (vs), 1582 (vs), 1482 (m), 1450 (m), 1410 (m), 1340 (m), 1299 (m) cm–1;
Elemental analysis calcd. (%) for C28H12O2: C 88.41, H 3.18; found: C 87.47, H 3.28.
7.2.4.12 [RuCl2(═C═C═(FN))(PPh3)2] (45)
[RuCl2(PPh3)3] (839 mg, 0.84 mmol) and 9-ethynylfluoren-9-ol (380 mg, 1.84 mmol) was dissolved in THF (50 mL) and stirred under reflux for 2 h. The solvent was removed in vacuo, the crude product was dissolved in CH2Cl2 (5 mL) and n-pentane (100 mL) was added. The resulting solution was stored overnight at 5 °C, the formed precipitate was filtered off, washed with n-pentane (3 × 50 mL) and dried in vacuo. Complex 45 was obtained as a red powder. Yield 650 mg (0.74 mmol, 88 %).
Ph3P Cl Ru C C C
Cl PPh3
184 ! ! Experimental Section ! !
A
Cl PPh3 C C C Ru Cl PPh3 Ph3P Cl Ru C C C
Ph3P Cl
Cl
Ph3P PPh3 C C C Ru Cl Cl Cl Ru C C C
Ph3P PPh3
B
1 1 H NMR (CDCl3, 300 MHz): δ = 7.78–6.82 ppm (m, 38H, PPh3, FN); H NMR (CD2Cl2, 13 300 MHz): δ = 7.74–6.87 (m, 38H, PPh3, FN) ppm; C NMR (CD2Cl2, 75 MHz): δ = 313.8
(Cα), 239.1 (Cβ), 148.6–126.7 (Cγ, C(PPh3), C(FN)) ppm (The equilibrium between the 16 VE complex and the two dimeric structures did not allow a definitive assignment of the aromatic
31 carbon atoms); P NMR (CDCl3, 122 MHz): δ = 29.1 ppm; IR (KBr): ṽ 1922 (m, C═C═C), 1599 (m), 1482 (m), 1434 (s) cm–1; MS (ESI-TOF, MeCN) m/z (%): 849.12 (100) [M – Cl]+,
+ 890.15 (28) [M – Cl + MeCN] ; Elemental analysis calcd. (%) for C51H38Cl2P2Ru: C 69.23, H 4.33; found: C 69.38, H 4.30.
31 2 45A, 45B: P NMR (CD2Cl2, 122 MHz): δ = 47.8 (d, JP,P = 35.6 Hz), 47.1 (d, 2 2 2 JP,P = 37.3 Hz), 37.3 (d, JP,P = 26.7 Hz), 34.8 (d, JP,P = 26.7 Hz) ppm.
7.2.4.13 [RuCl2(═C═C═(AO))(PPh3)2] (46)
[RuCl2(PPh3)3] (200 mg, 0.21 mmol) and 10-ethynyl-10-hydroxyanthracen-9-one (46) (150 mg, 0.64 mmol) were suspended in THF (50 mL) and stirred under reflux for 4 h. The solvent was removed in vacuo, the crude product was dissolved in CH2Cl2 (3 mL) and n-pentane (100 mL) was added. The resulting solution was stored overnight at 5 °C, the
185 ! ! Experimental Section ! ! resulting precipitate was filtered off, washed with n-pentane (3 × 50 mL) and dried in vacuo. Complex 46 was obtained as purple powder. Yield 159 mg (0.17 mmol, 83%).
Ph3P Cl Ru C C C O
Cl PPh3
A
Cl PPh3 O C C C Ru Cl PPh3 Ph3P Cl Ru C C C O
Ph3P Cl
Cl
Ph3P PPh3 O C C C Ru Cl Cl Cl Ru C C C O
Ph3P PPh3
B
1 13 H NMR (CDCl3, 300 MHz): δ = 8.26 – 6.75 ppm (m, 38H, PPh3, AO); C NMR (CDCl3,
75 MHz): δ = 321.0 (Cα), 271.9 (Cβ), 136.8 – 125.6 (Cγ, C(PPh3), C(AO)) ppm (The equilibrium between the 16 VE complex and the two dimeric structures did not allow a
31 definitive assignment of the aromatic carbon atoms); P NMR (CDCl3, 122 MHz): δ = 25.1 ppm; IR (KBr): ṽ 1904 (w, C═C═C), 1677 (s), 1590 (m), 1284 (s) cm–1; MS (ESI-
+ TOF, MeCN) m/z (%): 661.06 (100) [RuCl(PPh3)2] ; Elemental analysis calcd. (%) for
C58H38Cl2OP2Ru: C 68.42, H 4.20; found: C 69.52, H 4.38.
31 2 46A, 46B: P NMR (CDCl3, 122 MHz): δ = 48.3 (d, JP,P = 35.6 Hz), 46.8 (d, 2 2 2 JP,P = 37.9 Hz), 36.3 (d, JP,P = 26.7 Hz), 33.2 (d, JP,P = 26.7 Hz) ppm.
186 ! ! Experimental Section ! !
7.2.4.14 [RuCl2(═C═C═(PCO))(PPh3)2] (47)
A suspension of [RuCl2(PPh3)3] (287 mg, 0.30 mmol) and 13-ethynyl-13-hydroxypentacen-6- one (150 mg, 0.45 mmol) in THF (50 mL) was stirred under reflux for 3 h. The deep-blue solution was filtered and the solvent removed in vacuo. The residue was dissolved in CH2Cl2 (10 mL), precipitated by the addition of n-pentane (100 mL) and removed by filtration. This cycle was repeated three times and the product 47 was obtained as a dark-blue solid. Yield 235 mg (0.23 mmol, 77%).
Ph3P Cl Ru C C C O
Cl PPh3
187 ! ! Experimental Section ! !
A
Cl PPh3 O C C C Ru Cl PPh3 Ph3P Cl Ru C C C O
Ph3P Cl
Cl
Ph3P PPh3 O C C C Ru Cl Cl Cl Ru C C C O
Ph3P PPh3 B
1 H NMR (CDCl3, 300 MHz): δ = 8.87 (s, 1H, PCO–H), 8.54 (s, 1H, PCO–H), 8.01 (d,
3 JH,H = 8.3 Hz, 1H, PCO–H), 7.84 – 7.81 (m, 1H, PCO–H), 7.78 – 7.69 (m, 2H, PCO–H), 7.58 – 7.51 (m, 3H, Ar–H), 7.41 (s, 3H, Ar–H), 7.36 – 7.30 (m, 6H, Ar–H), 7.18 – 7.10 (m,
13 4H, Ar–H), 7.06 – 6.89 (m, 14H, Ar–H), 6.82 – 6.70 (m, 6H, Ar–H) ppm; C NMR (CDCl3,
75 MHz): δ = 298.3 (Cα), 238.5 (Cβ), 185.6 (C=O), 138.2 (Cγ), 137.2 – 126.6 (CAr) ppm (The equilibrium between the 16 VE complex and the two dimeric structures did not allow a
31 definitive assignment of the aromatic carbon atoms); P NMR (CDCl3, 122 MHz): δ = 29.0 –1 ppm; IR (CH2Cl2): ṽ 1918 (m, C=C=C), 1660 (s), 1617 (m), 1434 (s) cm ; MS (ESI-TOF, + CH2Cl2) m/z (%): 977.15 (100) [M – Cl] ; Elemental analysis calcd (%) for C60H42Cl2OP2Ru: C 71.15, H 4.18; found C 71.61, H 4.23.
31 2 47A, 47B: P NMR (122 MHz, CDCl3): δ = 47.8 (d, JP,P = 36.7 Hz), 46.1 (d, 2 2 2 JP,P = 36.7 Hz), 38.7 (d, JP,P = 25.6 Hz), 35.4 (d, JP,P = 27.8 Hz) ppm.
188 ! ! Experimental Section ! !
7.2.5 Ruthenium Heteroscorpionate Cumulenylidene Complexes as Molecular Slides
7.2.5.1 [Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48)
To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (363 mg, 0.40 mmol) in THF (50 mL) 2- ethynyl-6-methoxynaphthalene (150 mg, 0.82 mmol) was added and the reaction mixture was stirred at room temperature for 16 h. The solvent was reduced in vacuo to 5 mL until precipitation occurred. The precipitation was completed by storing in a freezer (–20 °C) for
24 h. The product was filtered off, washed with Et2O (3 × 20 mL) and n-pentane (20 mL) and dried in vacuo. The complex 48 was obtained as orange crystals. Yield: 287 mg (0.26 mmol, 64%).
Me Me N N O N O N Me Ru Me O Ph P Cl C 3 C Me H
1 3 H NMR (300 MHz, CD2Cl2): δ = 7.58 (t, 6H, JH,H = 9.1 Hz, o-PPh3), 7.43 (s, 1H, NAPH– 1 5 3 3 H ), 7.41 (s, 1H, NAPH–H ), 7.34 (t, 3H, JH,H = 7.5Hz, p-PPh3), 7.23 (t, 6H, JH,H = 7.2 Hz, 3 4 8 3 m-PPh3), 7.05 (m, 3H, NAPH–H , NAPH–H , NAPH–H ), 6.92 (d, 1H, JH,H = 8.4 Hz, NAPH–H7), 6.59 (s, 1H, CH), 5.99 (s, 1H, pz–H4´), 5.96 (s, 1H, pz–H4), 5.11 (d,
4 5´ 5 JH,P = 4.7 Hz, Hß), 3.88 (s, 3H, OMe), 2.53 (s, 3H, pz–Me ), 2.46 (s, 3H, pz–Me ), 2.39 (s, 3 3´ 13 3H, pz–Me ), 1.87 (s, 3H, pz–Me ) ppm; C NMR (75 MHz, CD2Cl2): δ = 363.2 (d, 2 – 6 3´ 3 JC,P = 24.8 Hz, Cα), 166.6 (CO2 ), 157.2 (NAPH–C ), 155.4 (pz–C ), 155.3 (d, JC,P = 2.0 Hz, 3 5´ 4 5 2 pz–C ), 141.6 (pz–C ), 140.9 (d, JC,P = 2.0 Hz, pz–C ), 134.6 (d, JC,P = 8.9 Hz, o-PPh3), 4a 1 4 133.0 (NAPH–C ), 132.8 (d, JC,P = 48.6 Hz, i-PPh3), 130.2 (d, JC,P = 2.0 Hz, p-PPh3), 129.5 8a 1 3 3 (NAPH–C ), 129.1 (NAPH–C ), 128.1 (d, JC,P = 8.9 Hz, m-PPh3), 127.9 (NAPH–C ), 126.6 (NAPH–C8), 125.9 (d, J = 3.0 Hz, NAPH–C4a), 122.9 (NAPH–C7), 118.5 (NAPH–C5), 115.8
4 2 4´ 3 4 (d, JC,P = 4.0 Hz, NAPH–C ), 109.1 (pz–C ), 109.0 (d, JC,P = 3.0 Hz, Cß), 106.1 (pz–C ), 68.9 (CH), 55.6 (OMe), 14.4 (pz–Me3´), 14.3 (pz–Me3), 11.5 (pz–Me5´), 11.3 (pz–Me5) ppm;
31 P NMR (122 MHz, CD2Cl2): δ = 37.3 ppm; IR (KBr): ṽ 3053 (w, CH), 2990 (w, CH), 2957 – –1 (w, CH), 2924 (w, CH), 1671 (s, as-CO2 ), 1635 (m), 1589 (m), 1562 (w, C═N) cm ; MS + + (ESI-TOF, CH2Cl2) m/z (%): 867.12 (100) [M + K] , 851.15 (15) [M + Na] , 829.16 (5)
189 ! ! Experimental Section ! !
+ [M + H] ; Elemental analysis calcd. (%) for C43H40ClN4O3PRu: C 62.35, H 4.87, N 6.76; found: C 61.75, H 5.00, N 6.34.
7.2.5.2 [Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49)
To a suspension of [Ru(bdmpza)Cl(PPh3)2] (14) (909 mg, 1.00 mmol) in THF (150 mL) 1-ethynylpyrene (500 mg, 2.21 mmol) was added and the reaction mixture was stirred at room temperature for 16 h. The solvent was reduced in vacuo to 30 mL until precipitation occurred. The precipitation was completed by storing in a freezer (–20 °C) for 24 h. The product was filtered off, washed with Et2O (3 × 20 mL) and n-pentane (20 mL) and dried in vacuo. The complex 49 was obtained as orange crystals. Yield: 544 mg (0.79 mmol, 79%).
Me Me N N O N O N Me Ru Me Ph P Cl C 3 CH
1 H NMR (400 MHz, CD2Cl2): δ = 8.09 (m, 2H, Pyr–H), 7.96 (m, 4H, Pyr–H), 7.91 (m, 1H, 3 3 Pyr–H), 7.85 (d, JH,H = 8.1 Hz, 1H, Pyr–H), 7.57 (m, 6H, o-PPh3), 7.51 (d, JH,H = 8.1 Hz, 1H, 4´ Pyr–H), 7.30 (m, 3H, p-PPh3), 7.18 (m, 6H, m-PPh3), 6.65 (s, 1H, CH), 6.00 (s, 1H, pz–H ), 4 4 5´ 5.93 (s, 1H, pz–H ), 5.78 (d, JH,P = 4.7 Hz, 1H, Hß), 2.55 (s, 3H, pz–Me ), 2.49 (s, 3H, pz– 5 3 3´ 13 Me ), 2.39 (s, 3H, pz–Me ), 1.88 (s, 3H, pz–Me ) ppm; C NMR (100 MHz, CD2Cl2): 2 – 3´ 3 5´ δ = 359.1 (d, JC,P = 23.1 Hz, Cα), 166.7 (CO2 ), 155.6 (pz–C ), 155.6 (pz–C ), 141.7 (pz–C ), 5 2 141.0 (pz–C ), 134.7 (d, JC,P = 9.0 Hz, o-PPh3), 131.9 (Pyr–C), 131.5 (Pyr–C), 132.6 (d, 1 4 JC,P = 47.6 Hz, i-PPh3), 129.4 (Pyr–C), 130.3 (d, JC,P = 2.6 Hz, p-PPh3), 128.1 (Pyr–CH), 3 128.1 (d, JC,P = 9.0 Hz, m-PPh3), 127.8 (Pyr–CH), 126.7 (Pyr–CH), 126.2 (Pyr–CH), 126.1 (Pyr–CH), 125.8 (Pyr–C), 125.6 (Pyr–C), 125.5 (Pyr–C), 125.4 (Pyr–C), 125.2 (Pyr–CH),
3 125.0 (Pyr–CH), 124.8 (Pyr–CH), 124.7 (Pyr–CH), 111.8 (d, JC,P = 2.6 Hz, Cß), 109.1 (pz– 4´ 4 4 3´ 3 C ), 109.1 (d, JC,P = 3.9 Hz, pz–C ), 69.0 (CH), 14.4 (pz–Me ), 14.4 (pz–Me ), 11.5 (pz– 5´ 5 31 Me ), 11.4 (pz–Me ) ppm; P NMR (122 MHz, CD2Cl2): δ = 37.1 ppm; IR (KBr): ṽ 3048
190 ! ! Experimental Section ! !
– (w, CH), 2955 (w, CH), 2922 (w, CH), 2853 (w, CH), 1672 (s, as-CO2 ), 1632 (m), 1621 (m), –1 + 1592 (m), 1562 (w, C═N) cm ; MS (ESI-TOF, CH2Cl2) m/z (%): 872.16 (100) [M] , 646.08 + (90) [M – C18H10] ; Elemental analysis calcd. (%) for C48H40ClN4O2PRu: C 66.09, H 4.62, N 6.42; found: C 65.93, H 5.18, N 5.88.
7.2.5.3 1-Phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51)
To a solution of pyrenophenone (50) (1.00 g, 3.27 mmol) in THF (60 mL) ethynylmagnesium bromide (2.09 g, 16.33 mmol, 5.0 eq.) was added. The solution was stirred for 16 h at room temperature and the reaction was quenched by the addition of water (50 mL). The solution was extracted with CH2Cl2 (3 × 20 mL), dried (Na2SO4) and the solvent was removed in vacuo. The product 51 was obtained as brownish tacky solid. Yield: 1.06 g (3.18 mmol, 97%).
H
OH
1 3 3 H NMR (300 MHz, CDCl3): δ = 8.68 (d, JH,H = 8.1 Hz, 1H, Pyr–H), 8.36 (d, JH,H = 9.4 Hz, 3 3 1H, Pyr–H), 8.17 (d, JH,H = 8.1 Hz, 1H, Pyr–H), 8.10 (d, JH,H = 7.7 Hz, 1H, Pyr–H), 8.02 (m, 3 4H, Pyr–H), 7.92 (d, JH,H = 7.7 Hz, 1H, p-Ph), 7.86 (m, 1H, Pyr–H), 7.58 (m, 2H, m-Ph), 7.28 13 (m, 2H, o-Ph), 3.86 (s, 1H, OH), 2.98 (s, 1H, CH) ppm; C NMR (75 MHz, CDCl3): δ = 145.0 (Pyr–C1), 136.3 (i-Ph), 131.7 (Pyr–C), 131.2 (Pyr–C), 130.4 (Pyr–C), 128.6 (m-Ph), 128.1 (Pyr–CH), 128.0 (Pyr–C), 127.8 (Pyr–CH), 127.4 (Pyr–CH), 126.9 (p-Ph), 126.6 (o- Ph), 126.1 (Pyr–CH), 125.8 (Pyr–CH), 125.4 (Pyr–CH), 125.4 (Pyr–CH), 124.7 (Pyr–C),
124.6 (Pyr–CH), 124.3 (Pyr–CH), 86.7 (Calkyne), 76.8 (Calkyne–H), 74.7 (C–OH) ppm; IR –1 (CH2Cl2): ṽ 3299 (s, OH), 2114 (w, C≡C) cm ; MS (ESI-TOF, CH2Cl2) m/z (%): 355.11 (30) [M + Na]+, 687.23 (100) [2 × M + Na]+, 1019.35 (5) [3 × M + Na]+; Elemental analysis calcd. (%) for C25H16O: C 90.33, H 4.85; found: C 89.43, H 4.54.
191 ! ! Experimental Section ! !
7.2.5.4 [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B)
[Ru(bdmpza)Cl(PPh3)2] (14) (1.82 g, 2.00 mmol) and 1-phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51) (500 mg, 1.55 mmol) were suspended in THF (50 mL) and stirred at room temperature for 4 d. The solvent of the red solution was removed in vacuo to yield the crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length
15 cm, Ø 4 cm), washed with a mixture of Et2O/n-pentane (1:1 v/v), eluted with
CH2Cl2/acetone (1:1 v/v) and the solvent was removed in vacuo. Separation of isomers was achieved by a second column (silica, length 25 cm, Ø 4 cm) with CH2Cl2/acetone (1:1 v/v) yielding a purple isomer 54A (allenylidene trans to pyrazole) and a red isomer 54B (allenylidene trans to carboxylate).
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me Ph P Cl C Ph P C Cl 3 C 3 C C C
A B
54A: Yield: 591 mg (0.62 mmol, 40%).
1 3 H NMR (400 MHz, CD2Cl2): δ = 8.28 (d, JH,H = 7.4 Hz, 1H, Ar–H), 8.22 (m, 3H, Ar–H), 3 3 8.11 (d, JH,H = 8.8 Hz, 1H, Ar–H), 8.04 (m, 2H, Ar–H), 7.98 (d, JH,H = 7.9 Hz, 1H, Ar–H), 3 3 3 7.87 (d, JH,H = 9.3 Hz, 1H, Ar–H), 7.74 (d, JH,H = 7.5 Hz, 2H, Ar–H), 7.69 (t, JH,H = 7.4 Hz, 3 1H, Ar–H), 7.45 (t, JH,H = 7.5 Hz, 6H, PPh3), 7.34 (m, 3H, PPh3), 7.22 – 7.08 (m, 6H, PPh3, 2H, Ar–H), 6.60 (s, 1H, CH), 6.05 (s, 1H, pz–H4´), 5.13 (s, 1H, pz–H4), 2.56 (s, 3H, pz–Me5´), 2.25 (s, 3H, pz–Me5), 1.89 (s, 3H, pz–Me3), 1.81 (s, 3H, pz–Me3´) ppm; 13C NMR (101 MHz,
2 – 3´ CD2Cl2): δ = 304.6 (d, JC,P = 26.3 Hz, Cα), 231.2 (Cβ), 166.8 (CO2 ), 155.8 (pz–C ), 154.5 (d, 3 3 5´ 4 5 JC,P = 2.6 Hz, pz–C ), 147.2 (pz–C ), 143.1 (d, JC,P = 2.6 Hz, pz–C ), 141.7 (Cγ), 139.9 (Ar– 1 3 C), 133.7 (d, JC,P = 47.3 Hz, i-PPh3), 134.3 (d, JC,P = 9.2 Hz, m-PPh3), 134.1 (Ar–C), 133.9
192 ! ! Experimental Section ! !
(Ar–C), 133.9 (Ar–CH), 133.4 (Ar–C), 132.2 (Ar–CH), 131.8 (Ar–C), 131.5 (Ar–C), 131.3
4 (Ar–C), 129.8 (d, JC,P = 6.6 Hz, p-PPh3), 129.3 (Ar–CH), 128.9 (m, Ar–CH), 128.6 (Ar–C),
128.1 (Ar–CH), 127.9 (Ar–CH), 127.7 (m, o-PPh3), 127.6 (Ar–CH), 126.6 (Ar–CH), 126.3 (Ar–CH), 125.4 (Ar–CH), 125.5 (Ar–CH), 125.4 (Ar–CH), 124.5 (Ar–C), 109.2 (pz–C4´),
4 4 3´ 3 5´ 108.0 (d, JC,P = 2.6 Hz, pz–C ), 69.1 (CH), 14.5 (pz–Me ), 12.9 (pz–Me ), 11.5 (pz–Me ), 5 31 11.0 (pz–Me ) ppm; P NMR (162 MHz, CD2Cl2): δ = 32.2 ppm; IR (CH2Cl2): ṽ 1918 (w, – –1 C═C═C), 1663 (s, as-CO2 ), 1559 (m, C═N) cm ; MS (ESI-TOF, CH2Cl2) m/z (%): 721.15 + + + (100) [M –PPh3 + Na] , 908.17 (0.3) [Ru(bdmpza)Cl(PPh3)2] , 960.19 (0.2) [M] ; Elemental analysis calcd. (%) for C55H44ClN4O2PRu: C 68.78, H 4.62, N 5.83; found: C 67.76, H 4.71, N 5.94.
54B: Yield: 327 mg (0.34 mmol, 22%).
1 H NMR (400 MHz, CD2Cl2): δ = 8.27 (m, 3H, Ar–H), 8.05 (m, 6H, Ar–H), 7.90 (d, 3 JH,H = 7.2 Hz, 2H, Pyr–H), 7.69 – 7.48 (m, 10H, Ar–H/PPh3), 7.48 (s, 2H, Ar–H), 7.17 – 7.07 4´ 4 (m, 6H, PPh3), 6.65 (s, 1H, CH), 5.69 (s, 1H, pz–H ), 5.32 (s, 1H, pz–H ), 2.56 (s, 3H, pz– Me5´), 2.29 (s, 3H, pz–Me5), 1.97 (s, 3H, pz–Me3), 1.39 (s, 3H, pz–Me3´) ppm; 13C NMR
2 – (75 MHz, CD2Cl2): δ = 315.6 (d, JC,P = 19.8 Hz, Cα), 241.9 (Cβ), 165.7 (CO2 ), 155.4 (pz– 3´ 3 3 5´ 4 5 C ), 154.2 (d, JC,P = 2.0 Hz, pz–C ), 147.4 (pz–C ), 146.4 (d, JC,P = 3.0 Hz, pz–C ), 143.1 2 1 (Cγ), 142.3 (Ar–C), 139.8 (Ar–C), 134.1 (d, JC,P = 8.9 Hz, o-PPh3), 133.4 (d, JC,P = 46.6 Hz, i-PPh3), 132.0 (Ar–CH), 131.9 (Ar–CH), 131.5 (Ar–C), 131.1 (Ar–C), 130.9 (Ar–C), 129.5 4 (d, JC,P = 8.9 Hz, p-PPh3), 129.0 (Ar–CH), 128.6 (Ar–CH), 128.5 (Ar–CH), 128.2 (Ar–C), 3 128.0 (Ar–CH), 127.6 (Ar–CH), 127.5 (d, JC,P = 9.9 Hz, m-PPh3), 126.9 (Ar–CH), 126.4 (Ar– CH), 125.5 (Ar–CH), 125.1 (Ar–C), 125.0 (d, J = 9.9 Hz, Ar–CH), 124.3 (Ar–CH), 124.2 (Ar–C), 108.3 (pz–C4´), 107.6 (d, J = 3.0 Hz, pz–C4), 69.2 (CH), 14.4 (pz–Me3´), 13.1 (pz–
3 5´ 5 31 Me ), 11.6 (pz–Me ), 10.8 (pz–Me ) ppm; P NMR (122 MHz, CD2Cl2): δ = 32.2 ppm; IR – –1 (CH2Cl2): ṽ 1916 (m, C═C═C), 1670 (s, as-CO2 ), 1565 (m, C═N) cm ; MS (ESI-TOF, + MeCN) m/z (%): 646.08 (100) [Ru(bdmpza)Cl(PPh3)] , 662.08 (52) + + [Ru(bdmpza)Cl(PPh3) + O] , 908.17 (37) [Ru(bdmpza)Cl(PPh3)2] , 917.21 (8) [M – + + CO2 + H] , 960.19 (14) [M] .
7.2.5.5 [Ru(bdmpza)Cl(PTA)(PPh3)] (55)
[Ru(bdmpza)Cl(PPh3)2] (14) (908 mg, 1.00 mmol) and PTA (157 mg, 1.00 mmol, 1.0 eq.) were suspended in THF (50 mL) and heated under reflux for 1 h. The solvent was reduced in
193 ! ! Experimental Section ! ! vacuo (5 mL) and the product was precipitated with n-pentane (3 × 50 mL). The residue was filtered off and dried in vacuo. The crude product was dissolved in CH2Cl2 and layered with n-pentane leading to a yellow crystalline solid (55) that can be filtered off. Yield: 720 mg (0.90 mmol, 90%).
Me Me N N O N O N Me Ru Me
Ph3P Cl P N N N
1 H NMR (400 MHz, CDCl3): δ = 7.66 (m, 6H, PPh3), 7.26 (m, 9H, PPh3), 6.40 (s, 1H, CH), 4´ 4 3 5.96 (s, 1H, pz–H ), 5.64 (s, 1H, pz–H ), 4.37 (d, JH,H = 13.1 Hz, 3H, PTA–H), 4.23 (d, 3 3 JH,H = 12.8 Hz, 3H, PTA–H), 3.89 (d, J = 15.2 Hz, 3H, PTA–H), 3.78 (s, 3H, PTA–H), 2.81 (s, 3H, pz–Me5´), 2.41 (br-s, 6H, pz–Me5, pz–Me3´), 1.59 (s, 3H, pz–Me3) ppm; 13C NMR
– 3 3´ 3 (75 MHz, CDCl3): δ = 168.4 (CO2 ), 158.3 (d, JC,P = 1.9 Hz, pz–C ), 155.7 (d, JC,P = 1.9 Hz, 3 5´ 5 1 pz–C ), 141.8 (pz–C ), 141.2 (pz–C ), 137.1 (d, JC,P = 40.5 Hz, i-PPh3), 134.7 (d, 3 4 3 JC,P = 9.7 Hz, o-PPh3), 129.3 (d, JC,P = 1.9 Hz, p-PPh3), 127.6 (d, JC,P = 9.0 Hz, m-PPh3), 4 4 4´ 3 109.5 (d, JC,P = 9.0 Hz, pz–C ), 109.5 (pz–C ), 73.1 (d, JC,P = 5.8 Hz, N–CH2–N), 69.1 (CH), 1 3´ 3 5´ 52.4 (d, JC,P = 14.8 Hz, P–CH2–N), 16.7 (pz–Me ), 14.0 (pz–Me ), 11.5 (pz–Me ), 11.5 (pz– 5 31 2 Me ) ppm; P NMR (162 MHz, CDCl3): δ = 41.2 (d, JP,P = 43.5 Hz, PPh3), –27.5 (d,
2 – –1 JP,P = 43.5 Hz, PTA) ppm; IR (CH2Cl2): ṽ 1661 (s, as-CO2 ), 1569 (m, C═N) cm ; MS (ESI- + TOF, CH2Cl2) m/z (%): 803.17 (100) [M] ; Elemental analysis calcd. (%) for
C36H42ClN7O2P2Ru × CH2Cl2: C 50.04, H 4.99, N 11.04; found: C 49.97, H 4.85, N 11.06.
7.2.5.6 [Ru(bdmpza)Cl(PTA)2] (56)
[Ru(bdmpza)Cl(PPh3)2] (14) (200 mg, 0.25 mmol) and PTA (86.0 mg, 0.55 mmol, 2.2 eq.) were suspended in THF (50 mL) and heated under reflux for 20 h. The solvent was reduced in vacuo (5 mL) and precipitated with Et2O (25 mL). The residue was filtered off and dried in vacuo yielding a pale yellow powder (56). Yield: 75 mg (0.11 mmol, 43%). The product shows contamination with unreacted PTA.
194 ! ! Experimental Section ! !
Me Me N N O N O N Me Ru Me P Cl P
N N N N N N
1 4 4´ H NMR (400 MHz, CD2Cl2): δ = 6.63 (s, 1H, CH), 5.79 (s, 2H, pz–H , pz–H ), 4.50 (m, 3 12H, N–CH2–N), 4.17 (t, JH,H = 14.6 Hz, 6H, P–CH2–N), 4.01 (m, 6H, P–CH2–N), 2.21 (s, 3H, pz–Me5´), 2.12 (s, 3H, pz–Me5), 1.80 (br s, 6H, pz–Me3´, pz–Me3) ppm; 13C NMR
– 3 3´ 5 5´ (75 MHz, CDCl3): δ = 170.3 (CO2 ), 147.3 (pz–C , pz–C ), 141.5 (pz–C , pz–C ), 106.8 (pz– 4 4´ 1 C , pz–C ), 74.7 (CH), 73.2 (m, N–CH2–N), 58.9 (d, JC,P = 13.9 Hz, P–CH2–N), 58.0 (d, 1 3 3´ 5 5´ 31 JC,P = 16.1 Hz, P–CH2–N), 13.6 (pz–Me , pz–Me ), 11.6 (pz–Me , pz–Me ) ppm; P NMR 31 (162 MHz, CDCl3): The P NMR revealed several multiplets that might be attributed to a – possible equilibrium of protonated PTA ligands; IR (CH2Cl2): ṽ 1662 (s, as-CO2 ), 1569 (m, –1 + C═N) cm ; MS (ESI-TOF, CH2Cl2) m/z (%):977.33 (30) [Ru + (bdmpza) + 4 × PTA] ;
Elemental analysis calcd. (%) for C24H39ClN10O2P2Ru: C 41.29, H 5.63, N 20.06; found: C 39.83, H 5.89, N 19.17.
7.2.5.7 [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B)
[Ru(bdmpza)Cl(PTA)(PPh3)] (55) (150 mg, 0.19 mmol) and 9-ethynyl-9-fluorenol (77.0 mg, 0.37 mmol) were suspended in THF (50 mL) and stirred at room temperature for 2 d. At room temperature no reaction occurs and the suspension was heated under reflux for 16 h leading to a dark red solution. The solvent was removed in vacuo to yield the crude product. The isomeric mixture was dissolved in CH2Cl2 (5 mL) and loaded on a column (silica, length
15 cm, Ø 4 cm), washed with a mixture of CH2Cl2/acetone (1:1 v/v) and the two structural isomers were separated with acetone/H2O (95:5 v/v) yielding a purple isomer 57A (allenylidene trans to pyrazole) Yield: 12.0 mg (0.02 mmol, 11%). The second isomer appears as a red spot 57B (allenylidene trans to carboxylate) but the amount of isolated complex did not allow further characterizations. The data reported in the following section belong to the structural isomer with the allenylidene unit positioned trans to the pyrazole moiety.
195 ! ! Experimental Section ! !
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me PTA Cl C PTA C Cl C C C C
A B
1 1 8 4 5 H NMR (300 MHz, CD2Cl2): δ = 7.76 (m, 4H, FN–H , FN–H , FN–H , FN–H ), 7.57 (d, 3J = 7.4 Hz, 2H, FN–H3, FN–H6), 7.17 (m, 2H, FN–H2, FN–H7), 6.60 (s, 1H, CH), 6.31 (s, 1H,
4´ 4 2 pz–H ), 6.04 (s, 1H, pz–H ), 4.52 (s, 6H, N–CH2–N), 4.24 (d, JH,H = 6.8 Hz, 6H, P–CH2–N), 2.89 (s, 3H, pz–Me5´), 2.58 (s, 3H, pz–Me5), 2.51 (s, 3H, pz–Me3´), 2.24 (s, 3H, pz–Me3) ppm;
13 2 – C NMR (75 MHz, CD2Cl2): δ = 294.2 (d, JC,P = 26.0 Hz, Cα), 230.3 (Cβ), 166.5 (CO2 ), 3’ 3 3 4b 4a 155.0 (pz–C ), 154.0 (d, JC,P = 2.7 Hz, pz–C ), 144.8 (FN–C ), 144.8 (FN–C ), 144.3 (FN– C9), 142.3 (Cpz-5’), 140.6 (d, 3J = 1.8 Hz, Cpz-5), 130.1 (FN–C2, FN–C7, FN–C3, FN–C6), 122.1
1 8 4 5 4´ 4 4 (FN–C , FN–C ), 121.2 (FN–C , FN–C ), 109.5 (pz–C ), 108.4 (d, JC,P = 2.7 Hz, pz–C ), 73.8 3 1 (d, JC,P = 6.0 Hz, 3 × N–CH2–N), 69.3 (CH), 52.1 (d, JC,P = 18.0 Hz, 3 × P–CH2–N), 16.1 3´ 3 5´ 5 31 (pz–Me ), 13.0 (pz–Me ), 11.5 (pz–Me ), 11.3 (pz–Me ) ppm; P NMR (162 MHz, CD2Cl2):
– –1 δ = – 37.8 ppm; IR (CHCl3): ṽ 1923 (m, C═C═C), 1654 (s, as-CO2 ), 1560 (w, C═N) cm ; MS (ESI-TOF, MeCN) m/z (%): 796.19 (33) [M + 2 × MeCN]+.
7.2.5.8 [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)] (58A/58B)
[Ru(bdmpza)Cl(PTA)(PPh3)] (55) (300 mg, 0.37 mmol) and 1-phenyl-1-(pyren-1-yl)prop-2- yn-1-ol (250 mg, 0.75 mmol) were suspended in THF (50 mL) and stirred under reflux for 16 h. The solvent was removed in vacuo to yield the crude product. The isomeric mixture was dissolved in CH2Cl2 (3 mL) and loaded on a column (silica, length 25 cm, Ø 4 cm), washed with a mixture of CH2Cl2/acetone (1:1 v/v) and the two structural isomers were separated with acetone/MeOH (9:1 v/v) yielding a purple isomer 58A (allenylidene trans to pyrazole) Yield: 14.0 mg (0.02 mmol, 5%). The second isomer appears as a red spot 58B (allenylidene trans to carboxylate) but the amount of isolated complex did not allow further characterizations. The data reported in the following section belong to the structural isomer with the allenylidene unit positioned trans to the pyrazole moiety. 196 ! ! Experimental Section ! !
Me Me Me Me N N N N O O N O N N O N Me Ru Me Me Ru Me PTA Cl C PTA C Cl C C C C
A B
1 3 H NMR (400 MHz, CD2Cl2): δ = 8.50 (d, JH,H = 9.3 Hz, 1H, Pyr–H), 8.25 (m, 4H, Pyr–H), 3 8.14 (m, 2H, Pyr–H), 8.07 (m, 2H, o-Ph–H), 8.03 (d, JH,H = 7.6 Hz, 1H, Pyr–H), 7.97 (d, 3 3 3 JH,H = 9.3 Hz, 1H, Pyr–H), 7.81 (t, JH,H = 7.5 Hz, 1H, p-Ph–H), 7.32 (t, JH,H = 7.6 Hz, 2H, 4´ 4 2 m-Ph–H), 6.48 (s, 1H, CH), 6.23 (s, 1H, pz–H ), 5.36 (s, 1H, pz–H ), 4.14 (d, JH,H = 13.1 Hz, 5´ 3H, N–CH2–N), 3.94 (m, 9H, N–CH2–N, P–CH2–N), 2.78 (s, 3H, pz–Me ), 2.51 (s, 3H, pz– 5 3´ 3 13 Me ), 2.29 (s, 3H, pz–Me ), 1.97 (s, pz–3H, Me ) ppm; C NMR (75 MHz, CD2Cl2): 2 – 3´ δ = 300.6 (d, JC,P = 26.3 Hz, Cα), 228.0 (Cβ), 166.9 (CO2 ), 154.5 (pz–C ), 154.2 (d, 3 3 1 JC,P = 1.8 Hz, pz–C ), 147.9 (d, J = 1.8 Hz, i-Ph–C), 143.5 (d, J = 2.6 Hz, Pyr–C ), 142.1 (pz– 5´ 4 5 C ), 140.0 (d, JC,P = 1.8 Hz, pz–C ), 139.6 (d, J = 2.6 Hz, Pyr–C), 132.0 (Pyr–C), 131.6 (d, J = 1.8 Hz, 2 × Pyr–C), 130.2 (m-Ph–C), 129.7 (Pyr–CH), 128.9 (o-Ph–C), 128.7 (Pyr–C), 128.5 (Pyr–CH), 128.4 (Pyr–CH), 128.1 (p-Ph–C), 126.9 (Pyr–CH), 126.4 (Pyr–CH), 125.9 (Pyr–CH), 125.7 (Pyr–CH), 125.5 (Pyr–CH), 124.8 (Pyr–CH), 124.6 (Pyr–C), 109.3 (pz–C4´),
4 4 3 108.0 (d, JC,P = 3.5 Hz, pz–C ), 73.3 (d, JC,P = 6.1 Hz, 3 × N–CH2–N), 69.1 (CH), 52.0 (d, 1 3´ 3 5´ JC,P = 17.5 Hz, 3 × P–CH2–N), 15.9 (pz–Me ), 12.8 (pz–Me ), 11.4 (pz–Me ), 11.1 (pz– 5 31 Me ) ppm; P NMR (162 MHz, CD2Cl2): δ = –34.5 ppm; IR (CHCl3): ṽ 1919 (m, C═C═C), – –1 + 1658 (s, as-CO2 ), 1565 (w, C═N) cm ; MS (ESI-TOF, CH2Cl2) m/z (%): 856.20 (9) [M] , 1012.27 (100) [M + PTA]+.
197 ! ! Experimental Section ! !
7.2.6 Intramolecular Scholl Reaction of Pyrenophenone
7.2.6.1 6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-one (63); 11H-Indeno[2,1-a]pyren-11- one (64)
This procedure was adapted from literature.[291, 345]
AlCl3 (8.20 g, 61.5 mmol) and NaCl (1.80 g, 30.8 mmol) were melted at 130°C under aerobic conditions. Pyrenophenone (50) (1.00 g, 3.26 mmol) was added under stirring in one portion and the mixture was heated to 170°C and stirred for further 20 min. The yellow substance turned to black and finally changed its colour to dark-red. After cooling to room temperature, water (100 mL) was carefully added to the mixture. The crude product was extracted with
CH2Cl2 (3 × 100 mL) and after removal of the solvent a brown powder was obtained.
Purification was achieved via column chromatography with CH2Cl2:n-pentane = 3:1 as eluent
(silica, Ø = 6 cm, L = 30 cm) allowing the isolation of 64 (Rf = 0.70) and almost pure 63
(Rf = 0.35). Purification of 5 was achieved via a second column chromatography step with pure CH2Cl2 as eluent (silica, Ø = 2 cm, L = 30 cm, Rf = 0.50).
O O
∗ C H2
6,6a-dihydro-11H-indeno[2,1-a]pyren-11-one (63); yield: 148 mg (0.483 mmo, 15%); red solid.
1 3 3 H NMR (CD2Cl2, 300 MHz): δ = 8.39 (d, JH,H = 9.6 Hz, 1H), 7.86 (dd, JH,H = 8.3 Hz, 3 3 3 3 JH,H = 2.8 Hz, 2H), 7.78 (dd, JH,H = 6.8 Hz, JH,H = 2.5 Hz, 1H), 7.65 (d, JH,H = 3.8 Hz, 2H), 3 3 7.55 (d, JH,H = 8.3 Hz, 1H), 7.47 (m, 3H), 7.23 (d, JH,H = 9.6 Hz, 1H), 4.31 (dd, 3 3 * 3 3 JX,A = 18.1 Hz, JX,M = 6.4 Hz, 1H, C H), 3.58 (dd, JM,A = 15.5 Hz, JM,X = 6.4 Hz, 1H, syn- 3 3 13 H), 2.99 (dd, JA,X = 17.9 Hz, JA,M = 15.8 Hz, 1H, anti-H) ppm; APT C NMR (CD2Cl2, 75.5 MHz): δ = 207.6 (CO), 150.8 (C), 142.6 (C), 139.7 (C), 138.3 (C), 134.0 (CH), 133.3 (CH), 132.5 (C), 131.3 (C), 130.6 (CH), 129.8 (CH), 129.7 (C), 128.6 (C), 128.3 (CH), 128. 2 (CH), 128.0 (CH), 127.6 (C), 127.0 (CH), 125.0 (CH), 124.9 (CH), 123.9 (CH), 38.9 (CH),
198 ! ! Experimental Section ! !
33.2 (CH2) ppm; IR (CHCl3): ṽ 1662 (m, C═O), 1620 (w, C═C), 1605 (m, C═C), 1597 (s, –1 + C=C) cm ; HRMS (ESI-TOF, MeOH/CH2Cl2) m/z (%): 307.1116 (100) [M + H] ; Mp.:
205–208°C; Elemental analysis calcd (%) for C23H14O: C 90.17, H 4.61; found: C 90.21, H 4.57.
11H-indeno[2,1-a]pyren-11-one (64); yield: 247 mg (0.812 mmol, 25%); yellow solid.
1 3 H NMR (CD2Cl2, 300 MHz): δ = 9.17 (d, JH,H = 9.2 Hz, 1H), 8.19 (m, 5H), 8.07 (d, 3 3 3 JH,H = 8.9 Hz, 1H), 7.99 (t, JH,H = 7.5 Hz, 1H), 7.73 (d, JH,H = 7.5 Hz, 1H), 7.66 (d, 3 3 3 3 JH,H = 7.1 Hz, 1H), 7.53 (dt, JH,H = 7.4 Hz, JH,H = 1.1 Hz, 1H), 7.33 (dt, JH,H = 7.3 Hz, 3 13 JH,H = 0.7 Hz, 1H) ppm; APT C NMR (CD2Cl2, 75.5 MHz): δ = 180.2 (CO), 144.8 (C), 144.5 (C), 142.9 (C), 140.9 (C), 136.7 (C), 134.9 (CH), 131.8 (CH), 131.4 (C), 130.9 (C), 130.8 (CH), 130.4 (C), 129.8 (CH), 128. 1 (CH), 127.9 (CH), 127.6 (CH), 126.9 (CH), 125.7 (C), 125.0 (C), 124.1 (CH), 123.3 (CH), 121.0 (CH), 116.8 (CH) ppm; IR (KBr): ṽ 1698 (s,
–1 CO), 1625 (m), 1611 (s), 1590 (s, C═C) cm ; HRMS (ESI-TOF, MeOH/CH2Cl2) m/z (%): 304.2624 (100) [M]+, 631.1679 (20) [2 × M + Na]+; Mp.: 245–248°C; Elemental analysis calcd (%) for C23H12O: C 90.77, H 3.97; found: C 90.23, H 3.90.
199
200
8 APPENDIX
201 ! ! Appendix ! !
8.1 Details of the Structure Determinations
A Bruker-Nonius Kappa CCD, an Agilent SuperNova (Dual Source) or a Bruker Smart APEXII diffractometer was used for data collection. Single crystals were coated with perfluoropolyether, picked with a glass fiber, and immediately mounted in the nitrogen cold gas stream of the diffractometer. The structures were solved by using direct methods and refined with full-matrix least squares against F2(Siemens SHELX-97).[374] A weighting
2 2 2 scheme was applied in the last steps of the refinement with w = 1/[σ (F0 ) + (aP) + bP] and 2 2 P = [2Fc + max(F0 ,0)]/3. Hydrogen atoms were included in their calculated positions and refined in a riding model. All further details and parameters of the measurements are summarized in Table 13 to Table 20. The structure pictures were prepared with the program Diamond 2.1e.[375-377] The unit cell of 25B contains one n-hexane molecule which has been treated as a diffuse contribution to the overall scattering without specific atom positions by SQUEEZE/PLATON.[378-379]
Compound Dissolved in Layered with
tBu [Ru(bdmpza)Cl( ISQ/IBQ)(PPh3)] (15) CH2Cl2/n-hexane n-hexane
[Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(CO)(PPh3)] (18B) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20B) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25B) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29B) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A) CH2Cl2 n-hexane
[Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) CH2Cl2 n-pentane
Pyrenophenone (50) CH2Cl2/n-hexane slow evaporation
[Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] CH2Cl2 n-hexane
([Ru(bdmpza)Cl(54B) PTA)(PPh3)] (55) CH2Cl2 n-hexane
6,6a-dihydro-11H-indeno[2,1-a]pyren-11-one CH2Cl2 Et2O
(1163H) -indeno[2,1-a]pyren-11-one (64) CH2Cl2/n-pentane slow evaporation Table 12. Solvents used for crystallization.
202 ! ! Appendix ! !
[Ru(bdmpza)Cl(tBuISQ/IBQ)- [Ru(bdmpza)Cl(ISQ/IBQ)-
(PPh3)] (15) (PPh3)] (16)
empirical formula C44H51ClN5O3PRu C36H35ClN5O3PRu × 0.25 CH2Cl2 formula weight [g mol–1] 865.39 774.41 crystal color / habit green block blue block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 10.9262(8) 9.777(3) b [Å] 12.5322(12) 12.733(3) c [Å] 17.0543(16) 14.860(4) α [°] 107.131(7) 91.91(2) β [°] 93.042(8) 102.05(3) γ [°] 111.744(7) 108.86(2) V [Å3] 2037.9(3) 1701.8(8) θ [°] 6.2-26.5 6.25-26.5 h min, max – 13 to 13 – 12 to 12 k min, max – 15 to 15 – 15 to 15 l min, max – 21 to 21 – 18 to 17 F(000) 900 793 –1 μ(Mo-Kα) [mm ] 0.536 0.67 crystal size [mm] 0.254 × 0.225 × 0.169 0.165 × 0.099 × 0.079 –3 Dcalcd [g cm ] 1.41 1.511 T [K] 150(2) 150(2) reflections collected 17293 15195 indep. reflections 8277 6951 obs. reflections (>2σI) 6961 4138 parameter 504 450 wt. Parameter a 0.0206 0.0681 wt. Parameter b 1.2936 0.0000
R1, wR2 (obsd.) 0.0316, 0.0661 0.0738, 0.1428
R1, wR2 (overall) 0.0435, 0.071 0.1389, 0.1703 Diff. Peak / hole [e/Å3] 0.358 / –0.502 1.29 / –0.748 Goodness-of-fit on F2 1.041 1.014
Table 13. Structure determination details of complexes 15 and 16.
203 ! ! Appendix ! !
[Ru(bdmpza)Cl(═C═C═(FN))- [Ru(bdmpza)Cl(═C═C═(FN))-
(PPh3)] (20A) (PPh3)] (20B)
empirical formula C45H38ClN4O2PRu × H2O C45H38ClN4O2PRu × 2 CH2Cl2 formula weight [g mol–1] 852.30 1004.14 crystal color / habit brown block red block crystal system orthorombic triclinic space group, Z Pbca (No. 61), 8 P–1 (No. 2), 2 a [Å] 15.534(3) 12.0270(10) b [Å] 19.993(4) 12.4223(6) c [Å] 24.814(5) 14.9179(13) α [°] 90 98.766(5) β [°] 90 95.117(8) γ [°] 90 97.919(6) V [Å3] 7707(3) 2167.9(3) θ [°] 6.21-26.5 6.21-26.5 h min, max – 19 to 19 – 13 to 15 k min, max – 24 to 24 – 15 to 15 l min, max – 30 to 31 – 18 to 18 F(000) 3504.0 1024.0 –1 μ(Mo-Kα) [mm ] 0.565 0.752 crystal size [mm] 0.320 × 0.141 × 0.094 0.250 × 0.170 × 0.102 –3 Dcalcd [g cm ] 1.469 1.538 T [K] 150(2) 150(2) reflections collected 62130 25952 indep. reflections 7851 8825 obs. reflections (>2σI) 6066 7812 parameter 506 554 wt. Parameter a 0.0116 0.0901 wt. Parameter b 17.0595 10.8236
R1, wR2 (obsd.) 0.0389, 0.0762 0.0654, 0.1739
R1, wR2 (overall) 0.0622, 0.0855 0.0737, 0.181 Diff. Peak / hole [e/Å3] 0.819 / –0.523 1.513 / –1.81 Goodness-of-fit on F2 1.172 1.061
Table 14. Structure determination details of complexes 20A and 20B.
204 ! ! Appendix ! !
[Ru(bdmpza)Cl(═C═C═(AO))- [Ru(bdmpza)Cl(═C═C═(AO))-
(PPh3)] (25A) (PPh3)] (25B)
empirical formula C46H38ClN4O3PRu × CH2Cl2 C46H38ClN4O3PRu formula weight [g mol–1] 947.22 862.29 crystal color / habit brown block red block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 12.7183(13) 12.1411(7) b [Å] 12.9619(4) 12.4107(11) c [Å] 14.5615(11) 14.8427(12) α [°] 86.985(5) 93.010(8) β [°] 69.949(6) 98.019(5) γ [°] 77.142(6) 98.291(5) V [Å3] 2197.7(3) 2185.4(3) θ [°] 6.22-26.5 6.2-26.5 h min, max – 15 to 15 – 15 to 15 k min, max – 16 to 16 – 15 to 15 l min, max – 18 to 18 – 18 to 18 F(000) 968 884 –1 μ(Mo-Kα) [mm ] 0.621 0.499 crystal size [mm] 0.307 × 0.168 × 0.112 0.305 × 0.282 × 0.254 –3 Dcalcd [g cm ] 1.431 1.310 T [K] 153(2) 150(2) reflections collected 54811 31254 indep. reflections 8972 8938 obs. reflections (>2σI) 8522 8005 parameter 585 509 wt. Parameter a 0.0188 0.0510 wt. Parameter b 6.5351 1.7391
R1, wR2 (obsd.) 0.0450, 0.1097 0.0315, 0.0932
R1, wR2 (overall) 0.0475, 0.1111 0.0362, 0.096 Diff. Peak / hole [e/Å3] 1.378 / –0.753 0.612 / –0.557 Goodness-of-fit on F2 1.233 1.089
Table 15. Structure determination details of complexes 25A and 25B.
205 ! ! Appendix ! !
[Ru(bdmpza)Cl(═C═C═(PCO))- [Ru(bdmpza)Cl(═C═C═(PCO))-
(PPh3)] (29A) (PPh3)] (29B)
empirical formula C54H42ClN4O3PRu × 2 CH2Cl2 C54H42ClN4O3PRu × 2 CH2Cl2 formula weight [g mol–1] 1132.26 1132.26 crystal color / habit violet plate yellow block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 12.4473(11) 12.3917(5) b [Å] 13.2515(10) 13.4181(7) c [Å] 15.4170(9) 15.9204(3) α [°] 82.283(6) 90.222(3) β [°] 83.333(6) 93.896(4) γ [°] 85.279(6) 109.245(17) V [Å3] 2497.1(3) 2492.46(17) θ [°] 6.2-26.5 6.2-26.5 h min, max – 15 to 15 – 14 to 15 k min, max – 16 to 16 – 16 to 16 l min, max – 19 to 18 – 19 to 16 F(000) 1156.0 1156 –1 μ(Mo-Kα) [mm ] 0.664 0.665 crystal size [mm] 0.272 × 0.154 × 0.113 0.223 × 0.226 × 0.389 –3 Dcalcd [g cm ] 1.506 1.509 T [K] 150(2) 153(2) reflections collected 46376 24746 indep. reflections 10207 10166 obs. reflections (>2σI) 7515 9079 parameter 662 662 wt. Parameter a 0.0243 0.0859 wt. Parameter b 3.7984 0.5338
R1, wR2 (obsd.) 0.0506, 0.091 0.029, 0.0742
R1, wR2 (overall) 0.0829, 0.1015 0.0351, 0.078 Diff. Peak / hole [e/Å3] 0.749 / –0.677 1.735 / –0.789 Goodness-of-fit on F2 1.037 1.054
Table 16. Structure determination details of complexes 29A and 29B.
206 ! ! Appendix ! !
[Ru(bdmpza)Cl(CO)(PPh3)] [Ru(bdmpza)Cl(═C═C═(BT))- (18B) (PPh3)] (37A)
empirical formula C31H30ClN4O3PRu C53H42ClN4O2PRu × 2 CH2Cl2 formula weight [g mol–1] 674.08 1104.25 crystal color / habit red block blue plate crystal system monoclinic triclinic
space group, Z P 21/n (No. 14), 4 P–1 (No. 2), 2 a [Å] 16.4731(10) 11.095(2) b [Å] 10.7331(8) 11.579(2) c [Å] 18.2521(13) 20.263(4) α [°] 90 103.341(18) β [°] 113.487(4) 92.260(13) γ [°] 90 94.627(16) V [Å3] 2959.7(4) 2520.1(8) θ [°] 6.2-26.5 6.21-26.5 h min, max – 12 to 20 – 13 to 13 k min, max – 9 to 13 – 14 to 14 l min, max – 22 to 20 – 25 to 25 F(000) 1376.0 1128.0 –1 μ(Mo-Kα) [mm ] 0.713 0.654 crystal size [mm] 0.165 × 0.135 × 0.120 0.216 × 0.143 × 0.139 –3 Dcalcd [g cm ] 1.513 1.455 T [K] 150(2) 150(2) reflections collected 19549 27332 indep. reflections 6050 10282 obs. reflections (>2σI) 4479 6684 parameter 374 644 wt. Parameter a 0.0368 0.0663 wt. Parameter b 3.7134 7.1940
R1, wR2 (obsd.) 0.0443, 0.0909 0.0792, 0.1699
R1, wR2 (overall) 0.073, 0.1019 0.1302, 0.1928 Diff. Peak / hole [e/Å3] 0.76 / –0.521 1.942 / –1.012 Goodness-of-fit on F2 1.021 1.047
Table 17. Structure determination details of complexes 18B and 37A.
207 ! ! Appendix ! !
[Ru(bdmpza)Cl(═C═CH(Pyr))- [Ru(bdmpza)Cl-
(PPh3)] (49) (═C═C═C(PhPyr))(PPh3)] (54B)
empirical formula C48H40ClN4O2PRu × C5H12 C55H44ClN4O2PRu formula weight [g mol–1] 1029.4 960.43 crystal color / habit red prism black block crystal system triclinic triclinic space group, Z P–1 (No. 2), 2 P–1 (No. 2), 2 a [Å] 11.995(6) 11.8575(4) b [Å] 15.01(3) 12.6866(5) c [Å] 15.12(6) 14.7270(4) α [°] 108.26(16) 89.741(3) β [°] 103.18(11) 84.460(2) γ [°] 94.47(7) 81.454(3) V [Å3] 2484(11) 2180.46(13) θ [°] 6.21-26.5 2.82-26.73 h min, max – 15 to 15 – 14 to 14 k min, max – 18 to 18 – 15 to 16 l min, max – 18 to 18 – 18 to 18 F(000) 1064 988 –1 μ(Mo-Kα) [mm ] 0.554 0.507 crystal size [mm] 0.249 × 0.211 × 0.202 0.2259 × 0.1757 × 0.1611 –3 Dcalcd [g cm ] 1.376 1.463 T [K] 150(2) 180(2) reflections collected 28077 19715 indep. reflections 10098 9197 obs. reflections (>2σI) 6629 8051 parameter 608 581 wt. Parameter a 0.0961 0.0169 wt. Parameter b 3.2770 2.4714
R1, wR2 (obsd.) 0.0746, 0.1735 0.0349, 0.0759
R1, wR2 (overall) 0.1257, 0.2024 0.0428, 0.0796 Diff. Peak / hole [e/Å3] 1.363 / –1.283 0.402 / –0.344 Goodness-of-fit on F2 1.027 1.102
Table 18. Structure determination details of complexes 49 and 54B.
208 ! ! Appendix ! !
[Ru(bdmpza)Cl(PTA)(PPh3)] (55) Pyrenophenone (50)
empirical formula C36H42ClN7O2P2Ru × CH2Cl2 C23H14O formula weight [g mol–1] 888.15 306.34 crystal color / habit yellow block yellow block crystal system orthorombic triclinic space group, Z Pbca (No. 61), 8 P–1 (No. 2), 2 a [Å] 20.263(3) 8.6960(5) b [Å] 9.0183(6) 8.9100(3) c [Å] 41.404(5) 11.1780(4) α [°] 90 69.723(3) β [°] 90 80.622(4) γ [°] 90 69.626(4) V [Å3] 7566.0(14) 760.71(6) θ [°] 6.21-27.5 2.97-27.49 h min, max – 26 to 25 – 11 to 11 k min, max – 11 to 11 – 11 to 11 l min, max – 53 to 53 – 14 to 14 F(000) 3648 320 –1 μ(Mo-Kα) [mm ] 0.756 0.08 crystal size [mm] 0.25 × 0.13 × 0.08 0.26 × 0.20 × 0.11 –3 Dcalcd [g cm ] 1.559 1.337 T [K] 150(2) 150(2) reflections collected 90917 21718 indep. reflections 8575 3482 obs. reflections (>2σI) 6344 2743 parameter 473 217 wt. Parameter a 0.0400 0.0836 wt. Parameter b 20.5593 0.1325
R1, wR2 (obsd.) 0.0504, 0.1036 0.0454, 0.1301
R1, wR2 (overall) 0.0797, 0.1146 0.061, 0.1434 Diff. Peak / hole [e/Å3] 1.007 / –1.318 0.358 / –0.293 Goodness-of-fit on F2 1.061 1.099
Table 19. Structure determination details of compounds 55 and 50.
209 ! ! Appendix ! !
6,6a-dihydro-11H-indeno[2,1- 11H-indeno[2,1-a]pyren-11-one a]pyren-11-one (63) (64)
empirical formula C23H14O C23H12O formula weight [g mol–1] 306.34 304.33 crystal color / habit red block yellow block crystal system orthorombic orthorombic
space group, Z Pna21 (No. 33), 4 P212121 (No. 19), 4 a [Å] 14.4440(18) 4.5831(8) b [Å] 7.484(4) 15.039(3) c [Å] 13.509(3) 20.610(4) α [°] 90 90 β [°] 90 90 γ [°] 90 90 V [Å3] 1460.3(9) 1420.6(4) θ [°] 3.2-27.52 1.98-27.19 h min, max – 18 to 18 – 5 to 2 k min, max – 9 to 9 – 19 to 19 l min, max – 17 to 13 – 26 to 26 F(000) 640 632 –1 μ(Mo-Kα) [mm ] 0.084 0.086 crystal size [mm] 0.22 × 0.16 × 0.12 0.24 × 0.18 × 0.14 –3 Dcalcd [g cm ] 1.393 1.423 T [K] 150(2) 150(2) reflections collected 16840 11834 indep. reflections 3115 3150 obs. reflections (>2σI) 2450 2385 parameter 217 217 wt. Parameter a 0.0636 0.074 wt. Parameter b 0.6588 0.0000
R1, wR2 (obsd.) 0.00546, 0.1231 0.0498, 0.1224
R1, wR2 (overall) 0.00774, 0.1362 0.0787, 0.1446 Diff. Peak / hole [e/Å3] 0.519 / –0.303 1.513 / –1.81 Goodness-of-fit on F2 1.069 1.106
Table 20. Structure determination details of compounds 63 and 64.
210 ! ! Appendix ! !
8.2 Cyclic Voltammetry
Figure 62. Cyclic voltammogram for complexes 14, 19B, 20A, 20B, 25A, 25B, 37A, 37B, 54A and 54B in n + CH2Cl2 with Bu4NPF6 (0.1 M) as supporting electrolyte at a scan rate of 100 mV/s (vs. Fc/Fc ) (* indicates signal corresponding to Fc/Fc+).
211 ! ! Appendix ! !
n Figure 63. Cyclic voltammogram for complex 29B in MeCN with Bu4NPF6 (0.1 M) as supporting electrolyte at a scan rate of 200 mV/s (vs. Fc/Fc+).
212 ! ! Appendix ! ! Compound Δ Δ Δ E E E E E E 1/2 1/2 1/2 i i i p p p pa pa pa a a a (mV) (mV) (mV)
/ / / (mV) (mV) (mV) i i i pc pc pc
processes reduction Ru(III) Ru(II)/
0.80 394 1 73 ------4
– 0.67 0.71 19 265 1631 92 82 - - - B
– – 0.45 0.76 0.94 20 389 1932 1273 85 64 73 A
– – 0.96 0.64 0.91 20 371 1937 1273 74 64 73 B
– – 0.99 0.94 0.98 25 466 1479 1013 74 73 64 A
– – 0.88 0.94 0.95 25 641 1315 91 82 83 870 B
– – 0.83 0.71 0.86 3 1914 1228 82 83 87 73 7A
– – 0.97 0.61 0.97 3 188 1859 1168 64 73 72 7B
– – 0.23 0.17 0.85 54A 105 252 2178 1548 64 73
– 0.07 0.55 54B 320 1182 64 64 - - -
n Table 21. Cyclic voltammograms were recorded at 20 °C in dichloromethane, with Bu4NPF6 (0.1 M) as electrolyte, potentials are given relatively to ferrocenium/ferrocene as internal standard, at a scan rate of 100 mV/s.
213 ! ! Appendix ! !
8.3 Myoglobin Assay of CORMs
1.0
0.8
0.6 ) O C (
.
q 0.4 e
0.2
0.0 0 200 400 600 800 t [min]
Figure 64. CO release of [Mn(bpzp)(CO)3] 4 in the dark measured via myoglobin assay.
1.4
1.2
1.0
) 0.8 O C (
.
q 0.6 e
0.4
0.2
0.0 0 50 100 150 200 250 300 350 400 450 t [min]
Figure 65. CO release of [MnBr(HPz)2(CO)3] 5 in the dark measured via myoglobin assay.
214 ! ! Appendix ! !
2.0
1.8
1.6
1.4
1.2 ) O
C 1.0 (
. q
e 0.8
0.6
0.4
0.2
0.0 0 50 100 150 200 250 300 350 t [min]
Figure 66. CO release of [Mn(HIm)3(CO)3]Br 6 in the dark measured via myoglobin assay.
215 ! ! Appendix ! !
8.4 List of Abbreviations and Symbols
!HOMO highest occupied molecular orbital !MeCN acetonitrile! !OAc acetate! AO anthrone APH aminophenol APT attached proton test Ar aryl bpy 2,2´-bipyridine br broad BT benzotetraphene calcd. calculated Cp cyclopentadienyl d doublet (NMR spectroscopy)! dd double doublet (NMR spectroscopy)! dec. decomposition! DFT density functional theory! DMSO dimethyl sulfoxide dppe 1.2-bis(diphenylphosphino)ethane dppm 1.1-bis(diphenylphosphino)methane EA elemental analysis! ESI electrospray ionization FN fluorene h hour Hbdmpza 2,2-bis(3,5-dimethylpyrazol-1-yl)acetic acid 2,2-Hbdmpzp 2,2-bis(3,5-dimethylpyrazol-1-yl)-propionic acid 3,3-Hbdmpzp 3,3-bis(3,5-dimethylpyrazol-1-yl)propionic acid Hbpza 2,2-bis(pyrazol-1-yl)acetic acid 3,3-Hbpzp 3,3-bis(pyrazol-1-yl)propionic acid Hz Hertz i ipso IBQ iminobenzoquinonate 216 ! ! Appendix ! !
IR infrared! ISQ iminobenzosemiquinonate J coupling constant! LUMO lowest unoccupied molecular orbital! m medium (IR spectroscopy)! m meta m multiplet (NMR spectroscopy)! M.p. melting point MLCT metal-to-ligand charge-transfer MS mass spectrometry n-BuLi n-butyllithium! NMR nuclear magnetic resonance o ortho OTF Trifluoromethanesulfonate p para PC pentacene PCO pentacenone Ph phenyl ppm parts per million! PTA 1,3,5-triaza-7-phosphaadamantane Pyr pyrene RCM ring closing metathesis s singlet (NMR spectroscopy)! s strong (IR spectroscopy)! t triplet (NMR spectroscopy)! tBu tert-butyl tBuAPH 2-amino-4,6-di-tert-butylphenol TD-DFT time-dependent density functional theory THF tetrahydrofuran Tol tolyl TON turnover number Tp hydridotris(pyrazol-1-yl)borato Tpm trispyrazolylmethane triphos 1,1,1-tris(diphenylphosphinomethyl)ethane
217 ! ! Appendix ! !
UV/Vis ultraviolet/visible ṽ wavenumber VE valence electron w weak δ chemical shift ε molar extinction coefficient
218 ! ! Appendix ! !
8.5 List of Compounds
[Mn(bpzp)(CO)3] (4)
[Mn(HIm)3(CO)3]Br (6)
[Ru(bdmpza)H(CO)2] (11A/11B)
[Ru(bdmpza)(CO)(μ2-CO)]2 (12)
[Ru(bpza)Cl(CO)2] (13)
[Ru(bdmpza)Cl(ISQ/IBQ)(PPh3)] (16) t [Ru(bdmpza)Cl(═C═C═C(Ph Bu2)2)(PPh3)] (19A/19B)
[Ru(bdmpza)Cl(═C═C═(FN))(PPh3)] (20A/20B) 10-Hydroxy-10-((trimethylsilyl)ethynyl)anthracen-9-one (23) 10-Ethynyl-10-hydroxyanthracen-9-one (24)
[Ru(bdmpza)Cl(═C═C═(AO))(PPh3)] (25A/25B)
[Ru(bdmpza)Cl(═C═C═(PCO))(PPh3)] (29A/29B)
[Ru(bdmpza)Cl(═C═CH(PCN))(PPh3)] (31) 7-((Trimethylsilyl)ethynyl)-7H-benzo[no]tetraphen-7-ol (35) 7-Ethynyl-7H-benzo[no]tetraphen-7-ol (36)
[Ru(bdmpza)Cl(═C═C═(BT))(PPh3)] (37A/37B) Bisanthenequinone (39)
[RuCl2(═C═C═(FN))(PPh3)2] (45)
[RuCl2(═C═C═(AO))(PPh3)2] (46)
[RuCl2(═C═C═(PCO))(PPh3)2] (47)
[Ru(bdmpza)Cl(═C═CH(6-methoxynaphthalene))(PPh3)] (48)
[Ru(bdmpza)Cl(═C═CH(Pyr))(PPh3)] (49) 1-Phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (51)
[Ru(bdmpza)Cl(═C═C═C(PhPyr))(PPh3)] (54A/54B)
[Ru(bdmpza)Cl(PTA)(PPh3)] (55)
[Ru(bdmpza)Cl(PTA)2] (56) [Ru(bdmpza)Cl(═C═C═(FN))(PTA)] (57A/57B) [Ru(bdmpza)Cl(═C═C═C(PhPyr))(PTA)] (58A/58B) 6,6a-Dihydro-11H-indeno[2,1-a]pyren-11-one (63) 11H-Indeno[2,1-a]pyren-11-one (64)
219
220
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10 DANKSAGUNG
241 ! ! Danksagung ! !
Mein besonderer Dank gilt meinem Doktorvater Prof. Dr. Nicolai Burzlaff für die Aufnahme in seine Arbeitsgruppe, das interessante Thema, die Freiräume, Themenbereiche neu zu erschließen und die Unterstützung durch zahlreiche Diskussionen diese Promotion zielführend zu bearbeiten. Ganz herzlich möchte ich mich auch bei Prof. Dr. Sjoerd Harder und insbesondere dessen Vorgänger Prof. Dr. Dr. h.c. mult. Rudi van Eldik für die unkomplizierte Aufnahme in den Lehrstuhl und das positive Arbeitsklima bedanken.
Weiterhin gebührt mein Dank allen Kooperationspartnern, mit denen ich während meiner Promotionsarbeit zusammenarbeiten durfte. Vielen Dank an Prof. Dr. Rik R. Tykwinski, Andreas Waterloo und Johanna Januszewski für die Bereitstellung einer Vielzahl an Propargylalkoholen und die Zusammenarbeit im Rahmen der resultierten Veröffentlichungen. Prof. Dr. Tim Clark und Christian Wick danke ich für die theoretischen Berechnungen im Rahmen des Projekts über die Scholl-Reaktion. Prof. Dr. Ulrich Schatzschneider und Dr. Hendrik Pfeiffer danke ich für die freundlichen Gespräche und die Messungen in Würzburg im Rahmen des CORM-Projekts. Ganz herzlich danke ich Jun.-Prof. Dr. Eike Hübner für die DFT-Berechnungen zu den Allenylidenkomplexen.
Des Weiteren gebührt mein Dank allen Mitarbeitern des Departments für Chemie und Pharmazie, die maßgeblich zum Gelingen dieser Arbeit beigetragen haben. Ich danke Dr. Achim Zahl und Jochen Schmidt, Dr. Frank Heinemann, Christina Wronna, Ursula Niegratschka, Dr. Carlos Dücker-Benfer, Dr. Jörg Sutter und Dr. Christian Färber, sowie allen Mitarbeitern der Werkstatt, der Glasbläserei und der Chemikalienausgabe. Nochmals bedanken möchte ich mich bei Olli und Max für das Messen der unzähligen Massenspektren und bei Johannes sowie Philipp für das Vermessen der Kristallstrukturen nach vorhergehenden Suchaktionen.
Ein Dank gilt meinen Laborpartnern, egal ob im 3. Stock oder Keller, Steffi, Andy, Viola, Susy und Fabi, die mich stets unterstützt haben und für eine angenehme Stimmung sowie interessante Diskussionen gesorgt haben. Danken möchte ich auch den Ehemaligen (Gazi, Stefan, Fatima, Tom, Sascha, Nico), den Aktuellen (Eva, Thomas, Tobi, Susy, Philipp) und den Neuen des AKs (Lisa, Marleen, Fabi, Stephan) für die kollegiale Zusammenarbeit und das positive Arbeitsklima. Bei Nico möchte ich mich noch einmal Bedanken für die Unterstützung während der gesamten Promotion, das Aufbauen wenn´s nicht nach Plan läuft und die lustige Zeit in unserem Bunker ohne Fenster „besonders gegen Ende“.
Der größte Dank gebührt jedoch meiner Freundin Lisa und meiner Familie, ohne deren Unterstützung und Hilfe in den letzten Jahren diese Dissertation nie gelungen wäre.
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