Ferrocenyl-Alkynes and Butadiynes: Reaction Behavior towards Cobalt and Iron Carbonyl Compounds
von der Fakultät für Naturwissenschaften der Technischen Universität Chemnitz genehmigte Dissertation zur Erlangung des akademischen Grades
doctor rerum naturalium (Dr. rer. nat.)
Vorgelegt von M.Sc. Grzegorz Paweł Filipczyk Geboren am. 07.01.1966 in Chorzów (Polen)
eingereicht am: 31.05.2017 Erstgutachter: Prof. Dr. Heinrich Lang Zweitgutachter: Prof. Dr. Klaus Stöwe Tag der Verteidigung: 04.12.2017
ii Bibliografische Beschreibung und Referat
Filipczyk, Grzegorz Paweł Ferrocenyl-Alkine und Butadiine: Reaktionsverhalten gegenüber Cobalt- und Eisencarbonyl-verbindungen
Technische Universität Chemnitz, Fakultät für Naturwissenschaften Dissertation, 2017, 155 Seiten.
Die vorliegende Dissertation beschreibt die Synthese und Charakterisierung von neuartigen perferrocenylierten, cyclischen Komplexen unter Anwendung der Cobalt- vermittelten Cyclomerisierung in Kombination mit einer C-H-Bindungsaktivierung als auch die Bildung von ferrocenylierten Phosphinoalkinid-Komplexen mit Eisen- und Cobaltcarbonylen. Die elektrochemischen Eigenschaften und die Elektronentransfer- prozesse zwischen den terminalen Ferrocenyleinheiten in den unterschiedlichen cyclischen Verbindungen wurden unter Einbeziehung der Struktur/chemischen Zusammensetzung der Brückenbausteine ermittelt.
Elf perferrocenylierte, cyclische Komplexe wurden mittels [2+2] bzw. [2+2+2] 5 5 Cyclomerisierung von 1,4-Diferrocenylbutadiin FcC≡C–C≡CFc (Fc = Fe(η -C5H4)(η - 5 C5H5)) unter Verwendung von Dicarbonylcyclopentadienylcobalt Co(η -C5H5)(CO)2 erhalten. Diese können in drei Gruppen unterteilt werden: (i) Produkte der Cyclodimerisierung mit zusätzlicher Kettenverlängerung, welche Cyclobutadienyl- einheiten als zentrale Brückenbausteine besitzen (3a,b und 4a,b), (ii) Produkte der Cyclodimerisierung mit gleichzeitiger CO-Insertion (6a,b,c und 7), und (iii) Produkte der Cyclotrimerisierung gefolgt von einem Ringschluss durch eine C-H-Bindungsaktivierung (5a,b,c). Die Optimierung der Reaktionsbedingungen wurde zur Ausbeutemaximierung der jeweiligen Verbindungsfamilien durchgeführt.
Ein weiterer Teil dieser Forschungsarbeit bezieht sich auf die verschiedenen Reaktionsmuster von (Ferrocenylethinyl)diphenylphosphan- mit zweikernigen Eisen- bzw. Cobaltcarbonylverbindungen in Form von Dieisennonacarbonyl und Dicobaltoctacarbonyl als Reagenzien. Dabei konnten sechs gemischte Carbonyl- und Ferrocenyl-funktionalisierte Phosphinoacetylid-Komplexe mit Eisen(0) und Cobalt(0) erhalten und charakterisiert werden.
Stichworte: Eisen, Cobalt, Ferrocenyl, Alkin, Cyclisierung, C–H Aktivierung, Eisencarbonyl, Cobaltcarbonyl, Phospinoalkin, P–C Bindungsspaltung, Elektrochemie, Spektro- Elektrochemie
iii Abstract
Filipczyk, Grzegorz Paweł Ferrocenyl-Alkynes and Butadiynes: Reaction Behavior towards Cobalt and Iron Carbonyl Compounds
Technische Universität Chemnitz, Fakultät für Naturwissenschaften PhD Thesis, 2017, 155 Pages
The present PhD study focuses on the synthesis and characterization of novel perferrocenylated cyclic complexes utilizing cobalt - mediated cyclomerization in combination with C–H bond activation as well as formation of ferrocenylated phosphino- alkyne compounds with iron and cobalt carbonyls. Electrochemical properties and electron-transfer processes between terminal ferrocenyl units in the diverse cyclic compounds are explored in relation to the chemical composition of the building blocks connecting them. Eleven perferrocenylated cyclic compounds were obtained via [2 + 2] and [2 + 2 + 2]
5 5 cyclomerization of 1,4-diferrocenylbutadiyne FcC≡C–C≡CFc (Fc = Fe(η -C5H4)(η -C5H5))
5 by the reaction with dicarbonylcyclopentadienylcobalt Co(η -C5H5)(CO)2. They are subdivided into three groups: (i) products of cyclodimerization with additional chain extension, possessing cyclobutadienyl moieties as a central linkage unit (3a,b and 4a,b), (ii) products of cyclodimerization with consecutive CO insertion (6a,b,c and 7), and (iii) products of cyclotrimerization followed by cycle formation via C–H bond activation (5a,b,c). Optimization of the reaction conditions was made in order to maximize the amount of each group of compounds. Furthermore, another part of this research work focuses on diverse reaction patterns of (ferrocenylethynyl)diphenylphosphane with diironnonacarbonyl and dicobaltocta- carbonyl. Six mixed carbonyl and ferrocenyl-functionalized phospinoalkynyl compounds of iron(0) and cobalt(0) were obtained and characterized.
Keywords: Iron, Cobalt, Ferrocenyl, Alkyne, Cyclization, C–H Activation, Iron Carbonyl, Cobalt Carbonyl, Phospinoalkyne, P–C Bond Cleavage, Electrochemistry, Spectro- electrochemistry.
iv Ort und Zeitraum der Durchführung
Die vorliegende Promotionsarbeit wurde in der Zeit von November 2010 bis Mai 2017 unter Leitung von Herrn Prof. Dr. Heinrich Lang am Lehrstuhl für Anorganische Chemie der Technischen Universität Chemnitz durchgeführt.
Herrn Prof. Dr. Heinrich Lang danke ich für die gewährten Freiheiten bei der Bearbeitung des Themas, die anregenden Diskussionen sowie für die großzügige Unterstützung dieser Arbeit und das mir entgegengebrachte Vertrauen.
v Widmung
Dem liebenden Gott,
meinen Eltern
und denen, die mit mir den Weg gegangen sind
vi Präambel
Im Rahmen der Promotionsarbeit an der Professur Anorganische Chemie der Technischen Universität Chemnitz konnten drei Publikationen erstellt werden. Diese sind bereits veröffentlicht. Alle Publikationen wurden unter Anleitung von Herrn Prof. Dr. Heinrich Lang und Dr. A. Hildebrandt selbstständig und in englischer Sprache verfasst. Im Falle von Publikationen, welche in arbeitsgruppeninterner Kooperation erstellt wurden, wird an entsprechender Stelle verwiesen. Die Zusatz - Informationen (Supporting Information) können auf den entsprechenden Internetseiten der Journale eingesehen werden.
Alle diese Promotionsschrift betreffenden Manuskripte sind in inhaltlich unveränderter Form als Kapitel C, D und E eingefügt worden. Die Zusammenfassungen dieser sind im Kapitel F als Anhänge A-C wiedergegeben. Die Kurzfassungen und Danksagungen sind als Anhänge D-F beigefügt. Die Kapitel A Einleitung (Introduction), Kapitel B Kenntnisstand (State of Knowledge) und Kapitel F Zusammenfassung (Summary) sowie die Abschnitte Inhaltsverzeichnis (Table of Contents), Abkürzungen (List of Abbreviations) und Anhang (Appendix) sind in englischer Sprache erstellt worden. Weiterhin erfolgt die Nummerierung der in der Dissertationsschrift aufgeführten chemischen Verbindungen gemäß der Bezeichnung des Manuskriptes, in welchem die wissenschaftlichen Ergebnisse veröffentlicht wurden.
vii Table of contents
Bibliografische Beschreibung und Referat ...... iii
Abstract ...... iv
Ort und Zeitraum der Durchführung ...... v
Widmung ...... vi Präambel ...... vii
List of Abbreviations ...... xii CHAPTER A Introduction ...... 15
References ...... 16 CHAPTER B State of Knowledge ...... 19
1 (Spectro)electrochemical studies of mixed-valent transition metal complexes. Theoretical background ...... 19
1.1 Mixed-valent compounds – classification ...... 20
1.2 Spectroelectrochemistry ...... 21
1.3 Electrochemistry...... 25
2 (Di)ferrocenylalkynes – synthesis and reactions ...... 28
2.1 1,4-Diferrocenylbutadiyne ...... 29 2.2 Other (poly)ferrocenyl substituted alkyne derivatives ...... 35
3 Dicarbonylcyclopentadienylcobalt – [2+2] and [2+2+2] cyclo-addition reactions 37 3.1 [2+2] and [2+2+2] cycloaddition – cyclobutadiene, cyclopentadienone, benzene and pyridine based systems ...... 38
3.2 Mechanism of [2+2] and [2+2+2] cycloaddition/cyclization and [2+2]
cycloaddition/cyclization with CO insertion mediated by CoCp(CO)2 ...... 40
4 Chelation-assisted C–H bond activation mediated by cobalt species ...... 42 5 Phosphinoalkynes and their reaction with iron and cobalt carbonyls ...... 44
5.1 Mechanism of the P–C(sp) bond cleavage in phosphinoalkynes ...... 48 6 Complexes setup by (ferrocenylethynyl)diphenylphosphane ...... 50
References ...... 56 CHAPTER C Multiferrocenyl Cobalt-Based Sandwich Compounds...... 64
1 Introduction ...... 64
2 Results and Discussion ...... 65
2.1 Synthesis and Characterization ...... 65
viii 2.2 Solid-State Structures ...... 71
2.3 Electrochemistry...... 73
2.4 Spectroelectrochemistry ...... 76 3 Experimental Section ...... 79
3.1 Instrumentation ...... 79 3.2 General Conditions ...... 81
3.3 Reagents ...... 81 3.4 General Procedure - Reaction of 1 with 2 ...... 81 3.4.1 Compound 3a...... 82 3.4.2 Compound 3b ...... 83 3.4.3 Compound 4b ...... 83 3.4.4 Compound 5c ...... 83 3.4.5 Compound 6a...... 84 3.4.6 Compound 6b ...... 84 3.4.7 Compound 6c ...... 85 3.4.8 Compound 7 ...... 85
4 Supporting information ...... 86
5 References ...... 86
CHAPTER D Combining Cobalt-Assisted Alkyne Cyclotrimerization and Ring Formation through C–H Bond Activation: A “One-Pot” Approach to Complex Multimetallic Structures ...... 91
1 Introduction ...... 91 2 Results and Discussion ...... 92
3 Experimental Section (Supporting information) ...... 98
3.1 General Information ...... 98
3.2 Starting Materials ...... 98
3.3 Synthesis of 3a and 3b from 2...... 99 3.3.1 Complex 3a: ...... 99 3.3.2 Complex 3b: ...... 100 3.4 Synthesis of 9a and 9b from 1-Ferrocenylethynyl-2-Ferrocenyl Benzene (8) ... 101 3.4.1 Synthesis of 1-Bromo-2-Ferrocenylethynyl Benzene (7) ...... 101 3.4.2 Synthesis of 1-Ferrocenylethynyl-2-Ferrocenyl Benzene (8) ...... 102 3.4.3 Synthesis of 9a and 9b from 8 ...... 103
3.5 Synthesis of 3a and 3b from 1,3,5-Triethynylferrocenyl-2,4,6-Triferrocenyl Benzene (4) ...... 105 3.5.1 Synthesis of 1,3,5-Trichloro-2,4,6-Triethynylferrocenyl Benzene (12) ...... 105 3.5.2 Synthesis of 1,3,5-Triethynylferrocenyl-2,4,6-Triferrocenyl Benzene (4) .. 105 3.5.3 Synthesis of 3a and 3b from 4 ...... 106
ix 4 Supporting information ...... 107
4.1 Spectroelectrochemistry of 3a,b ...... 107
4.2 Conversion of Isomer 9a to 9b – Electrochemical and Chemical oxidation...... 109 4.3 Chemical oxidation experiment...... 110
5 References ...... 111 CHAPTER E Coordination Behavior of (Ferrocenylethynyl)diphenyl-phosphane Towards Binuclear Iron and Cobalt Carbonyls ...... 114
1 Introduction ...... 114
2 Results and Discussion ...... 115
3 Experimental Section ...... 126 3.1 Instrumentation ...... 126
3.2 General ...... 128 3.3 Reagents ...... 128
3.4 Synthesis of 4 ...... 128
3.5 Synthesis of 4, 5 and 6 ...... 129 3.6 Synthesis of 6 by reacting 4 with 2 ...... 131
3.7 Synthesis of 7 and 8 ...... 131 3.8 Synthesis of 8 from 1 with 3...... 132
3.9 Synthesis of 9 in the reaction of 7 with 2 ...... 133 3.10 Synthesis of 9 in the reaction of 4 with 3 ...... 133
4 Electronic Supplementary Material (Supporting information) ...... 134
5 References ...... 134
CHAPTER F Summary ...... 139
1 Conclusions of Chapter C (Appendix A) ...... 139 2 Conclusions of Chapter D (Appendix B) ...... 141
3 Conclusions of Chapter E (Appendix C) ...... 142 Appendix ...... 145
1 Appendix D (Chapter C) ...... 145
2 Appendix E (Chapter D) ...... 146
3 Appendix F (Chapter E) ...... 147
Curriculum Vitae ...... 150
Publications ...... 152 Acknowledgements ...... 154
x Selbstständigkeitserklärung ...... 155
xi List of Abbreviations
Scientific abbreviations EA elemental analysis E potential energy f the force constant of the M-L bond vibrations fac facial G Gibbs free-energy H enthalpy K equilibrium constant LMCT ligand-to-metal charge transfer mer meridional MLCT metal-to-ligand charge transfer NIR near infrared r the average of the metal-ligand bond length rac racemic mixture S entropy or solvent UV/Vis ultraviolet - visible α angle between the axis z and y β angle between the axis x and z γ angle between the axis x and y
Common abbreviation eg for example rt room temperature
Compounds Bipy bipyridine cod cycloocta-1,5-diene cy cyclohexane imi imidazole LDA lithium diisopropylamine MeLi methyllithium
xii ph phenyl PhLi phenyllithium PVC polyvinyl chloride py pyridine tBuLi tert-buthyllithium thf tetrahydrofuran tht tetrahydrothiophene TMEDA tetramethylethylenediamine TMS tetramethylsilane
Spectroscopy COSY 2D NMR include correlation Spectroscopy d doublet dd doublet of doublet dt doublet of triplet Ea activation energy FTIR fourier transform infrared spectroscopy H proton J coupling constant m multiplet M molar mass m/z mass-to-charge ratio
μeff Magnetic effective moment n Number of unpaired electron NMR Magnetic Nuclear Resonance NOESY nuclear overhauser effect spectroscopy q quartet
o density of the pure solvent and
s density of the solution chemical shift s singlet, or second relaxation time t triplet
xiii Units and constants Å Ångstrom °C degree Celsius C concentration (mol/L) Hz Hertz J Joule K Kelvin
KB Boltzmann constant ns nanosecond ppm part per millom R gas constant
(Spectro)electrochemistry α delocalization parameter CV Cyclic Voltammetry D diffusion rate
ΔE1/2 half-wave potential splitting
Δν1/2 bandwidth at half-hight
Epa anodic wave
Epc cathodic wave
εmax intensity of the band at its maximum Γ classification parameter
Hab electronic coupling parameter
ip current density IT Intervalence-Transfer IVCT Inter-Valence-Charge-Transfer λ reorganization energy parameter LMCT Ligand-to-Metal-Charge-Transfer MLCT Metal-to-Ligand-Charge-Transfer OTTLE Optically Transparent Thin-Layer Electrochemistry
rab effective distance SWV Square-Wave Voltammetry
νmax energy of the transition v potential scan rate (sweep rate)
xiv CHAPTER A Introduction
Transition metal complexes bridged by π-conjugated organic building blocks have found considerable attention in the research field of organometallic chemistry as they give a very good platform for the study of electron transfer processes in mixed-valent compounds,[A1–9] which is especially important for the development of components of molecular electronic circuits.[A2,10–25]
Particularly attractive in this field of research is ferrocene and its derivatives, because of its very good electrochemical reversibility (redox reproducibility) and high stability at different oxidation states (Fe2+/Fe3+) during redox processes.[A8,26–31] Furthermore, the oxidation state of iron has a small effect on interatomic distances in ferrocene and ferrocenium salts and therefore the redox process does not cause a great change on coordination geometry around iron.[A32,33] The similarity of the coordination geometry of the interacting sites supports rapid electron transfer in the studied system.[A33,34] Therefore, the use of ferrocenyl moieties is of great value in the examination of the communication ability between two or more interacting redox active centers in relation to the distance between them, the nature of the bridging ligands and the extend of conjugation, or their relative orientation as well as to additional ligands present.[A7,35–40]
A popular molecular unit utilized as a connector and bridging ligand between ferrocenyl groups or other redox active centers is the ethynyl/alkynyl –C≡C– linker, which allows π-conjugation.[A41–49] Additionally, the use of such linkers, as for example acetylene derivatives, polyacetylenes or phosphinoacethylens is highly advantageous because of their ability to create a variety of extended structures of organic or organometallic compounds. This can be achieved via cycloaddition processes by applying low valent cyclopentadienyl-cobalt [CpCo] species as a catalyst or reagent.[A50–63]
This study aims to use the [2+2] and [2+2+2] cyclization method for cyclization of 1,4- diferrocenylbutadiyne by applying dicarbonylcyclopentadienylcobalt in combination with C–H bond activation assisted by low-valent cyclopentadienyl cobalt species to form novel cyclic perferrocenyleted organometallic compounds. Furthermore, the various modes of reaction of acetylenes and phosphinoacetylenes towards iron- and cobaltcarbonyl compounds were used to obtain ferrocenylated phosphinoalkyne complexes of cobalt and
15 iron. The (spectro)electro-chemical properties of the new compounds are explored in order to study the electron transfer processes in the mixed-valent compounds.
A brief overview of the topics and results of former research related to this Ph.D. thesis is presented in Chapter B.
References
[A1] M. B. Robin, P. Day, Adv. Inorg. Chem. Radiochem. 1967, 10, 247–422.
[A2] S. Barlow, D. O’Hare, Chem. Rev. 1997, 97, 637–670.
[A3] D. B. Brown, Ed., Mixed Valence Compounds, D. Reidel Publishing Co., Boston, 1980.
[A4] P. Mücke, M. Linseis, S. Záliš, R. F. Winter, Inorg. Chim. Acta 2011, 374, 36–50.
[A5] B. S. Brunschwig, C. Creutz, N. Sutin, Chem. Soc. Rev. 2002, 31, 168–184.
[A6] C. Lapinte, J. Organomet. Chem. 2008, 693, 793–801.
[A7] P. Aguirre-Etcheverry, D. O’Hare, Chem. Rev. 2010, 110, 4839–4864.
[A8] A. Hildebrandt, H. Lang, Organometallics 2013, 32, 5640–5653.
[A9] A. Hildebrandt, U. Pfaff, H. Lang, Rev. Inorg. Chem. 2011, 31, 111–141.
[A10] C. Engtrakul, L. R. Sita, Organometallics 2008, 27, 927–937.
[A11] F. Paul, C. Lapinte, Coord. Chem. Rev. 1998, 178–180, 431–509.
[A12] J. Jiang, J. R. Smith, Y. Luo, H. Grennberg, H. Ottosson, J. Phys. Chem. C 2011, 115, 785–790.
[A13] R. L. Carroll, C. B. Gorman, Angew. Chem. Int. Ed. 2002, 41, 4378–4400.
[A14] A. Aviram, M. A. Rather, Chem. Phys. Lett. 1974, 29, 277–283.
[A15] A. Nitzan, M. A. Ratner, Science 2003, 300, 1384–1389.
[A16] D. K. James, J. M. Tour, Chem. Mater. 2004, 16, 4423–4435.
[A17] J. Jortner, M. A. Ratner, Molecular Electronics, Blackwell Science, Oxford, 1997. [A18] B. Kim, J. M. Beebe, C. Olivier, S. Rigaut, D. Touchard, J. G. Kushmerick, X.-Y. Zhu, D. Frisbie, J. Phys. Chem. C 2007, 111, 7521–7526.
[A19] P. J. Low, Dalton Trans. 2005, 2821–4.
[A20] A. Aviram, M. A. Ratner, Chem. Phys. Lett. 1974, 29, 277–283.
[A21] C. S. Lent, B. Isaksen, M. Lieberman, J. Am. Chem. Soc. 2003, 125, 1056–1063.
16 [A22] M. D. Ward, Chem. Soc. Rev. 1995, 24, 121–134.
[A23] F. Barigelletti, L. Flamigni, Chem. Soc. Rev. 2000, 1–12.
[A24] M. Akita, T. Koike, Dalton Trans. 2008, 9226, 3523–30.
[A25] N. Robertson, C. A. McGowan, Chem. Soc. Rev. 2003, 32, 96–103.
[A26] C. Levanda, K. Bechgaard, D. O. Cowan, J. Org. Chem. 1976, 41, 2700–2704.
[A27] K. Heinze, H. Lang, Organometallics 2013, 32, 5623–5625.
[A28] K. M. Kadish, Q. Y. Xu, J. M. Barbe, Inorg. Chem. 1987, 26, 2566–2568.
[A29] N. G. Connelly, W. E. Geiger, Chem. Rev. 1996, 96, 877–910.
[A30] D. Astruc, C. Ornelas, J. Ruiz, Acc. Chem. Res. 2008, 41, 841–856.
[A31] C. M. Casado, I. Cuadrado, M. Morán, B. Alonso, B. Garcia, B. Gonzalez, J. Losada, Coord. Chem. Rev. 1999, 185–186, 53–79.
[A32] M. Rosenblum, Chemistry of the Iron Group Metallocenes, Wiley, New York, 1965.
[A33] C. LeVanda, K. Bechgaard, D. O. Cowan, U. T. Mueller-Westerhoff, P. Eilbracht, G. A. Candela, R. L. Collins, J. Am. Chem. Soc. 1976, 98, 3181–3187.
[A34] N. S. Hush, Prog. Inorg. Chem. 1967, 8, 391–444.
[A35] C. Levanda, K. Bechgaard, D. O. Cowan, J. Org. Chem. 1976, 41, 2700–2704.
[A36] J. Kotz, G. Neyhart, W. J. Vining, M. D. Rausch, Organometallics 1983, 2, 79–82.
[A37] M. J. Powers, T. J. Meyer, J. Am. Chem. Soc. 1978, 100, 4393–4398.
[A38] J. A. Kramer, D. N. Hendrickson, Inorg. Chem. 1980, 19, 3330–3337.
[A39] D. O. Cowan, C. LeVanda, J. Park, F. Kaufman, Acc. Chem. Res. 1973, 6, 1–7.
[A40] W. H. Morrison, D. N. Hendrickson, Inorg. Chem. 1975, 14, 2331–2346.
[A41] M. I. Bruce, P. J. Low, K. Costuas, J. F. Halet, S. P. Best, G. A. Heath, J. Am. Chem. Soc. 2000, 122, 1949–1962.
[A42] F. de Montigny, G. Argouarch, K. Costuas, J.-F. Halet, T. Roisnel, L. Toupet, C. Lapinte, Organometallics 2005, 24, 4558–4572.
[A43] M. Lohan, P. Ecorchard, T. Ru, C. Lapinte, Organometallics 2009, 28, 1878–1890. [A44] M. I. Bruce, M. L. Cole, K. Costuas, B. G. Ellis, K. A. Kramarczuk, C. Lapinte, B. K. Nicholson, G. J. Perkins, B. W. Skelton, A. H. White, N. N. Zaitseva, Z. Anorg. Allg. Chem. 2013, 639, 2216–2223.
[A45] M. I. Bruce, K. A. Kramarczuk, B. W. Skelton, A. H. White, J. Organomet. Chem. 2010, 695, 469–473.
[A46] M. I. Bruce, K. Costuas, B. G. Ellis, J. F. Halet, P. J. Low, B. Moubaraki, K. S. Murray, N. Ouddai, G. J. Perkins, B. W. Skelton, A. H. White, Organometallics 2007, 26, 3735– 3745.
17 [A47] M. I. Bruce, K. Costuas, T. Davin, J.-F. Halet, K. A. Kramarczuk, P. J. Low, B. K. Nicholson, G. J. Perkins, R. L. Roberts, B. W. Skelton, M. E. Smith, A. H. White, Dalton Trans. 2007, 2, 5387–99.
[A48] M. I. Bruce, Coord. Chem. Rev. 1997, 166, 91–119.
[A49] Z. Yuan, G. Stringer, I. R. Jobe, D. Kreller, K. Scott, L. Koch, N. J. Taylor, T. B. Marder, J. Organomet. Chem. 1993, 452, 115–120.
[A50] P. R. Chopade, J. Louie, Adv. Synth. Catal. 2006, 348, 2307–2327.
[A51] N. Singh, A. J. Elias, Dalton Trans. 2011, 40, 4882–4891.
[A52] N. Singh, A. J. Elias, J. Chem. Sci. 2011, 123, 853–860.
[A53] H. V Nguyen, M. R. Yeamine, J. Amin, M. Motevalli, C. J. Richards, J. Organomet. Chem. 2008, 693, 3668–3676.
[A54] C. Schaefer, D. B. Werz, T. H. Staeb, R. Gleiter, F. Rominger, Organometallics 2005, 24, 2106–2113.
[A55] M. D. Rausch, F. A. Higbie, G. F. Westover, A. Clearfield, R. Gopal, J. M. Troup, I. Bernal, J. Organomet. Chem. 1978, 149, 246–264.
[A56] M. D. Rausch, R. A. Genetti, J. Org. Chem. 1970, 35, 3888–3897.
[A57] M. J. Calhorda, P. J. Costa, K. A. Kirchner, Inorg. Chim. Acta 2011, 374, 24–35.
[A58] Y.-Q. Wang, L.-M. Han, Q.-L. Suo, N. Zhu, F.-W. Li, Polyhedron 2014, 71, 42–46.
[A59] J. A. Varela, C. Saá, Chem. Rev. 2003, 103, 3787–3801.
[A60] Y. Wakatsuki, O. Nomura, K. Kitaura, M. Keiji, H. Yamazaki, J. Organomet. Chem. 1983, 105, 1907–1912.
[A61] T. D. Coyle, R. B. King, E. Pitcher, S. L. Stafford, P. Treichel, F. G. A. Stone, J. lnorg. Nucl. Chem. 1961, 20, 172–173.
[A62] A. Stockis, R. Hoffmann, J. Am. Chem. Soc. 1980, 102, 2952–2962.
[A63] N. Agenet, V. Gandon, K. P. C. Vollhardt, M. Malacria, C. Aubert, J. Am. Chem. Soc. 2007, 129, 8860–8871.
18 CHAPTER B State of Knowledge
The purpose of this chapter is to give an introduction to electro- and spectroelectrochemical measurement methods, which are commonly applied in the investigation of the processes occurring in the mixed-valent state. In addition a brief overview of the following aspects is given: the preparation and chemical properties of (di)ferrocenylated polyacetylenes, reactions of dicarbonylcyclopentadienylcobalt half- sandwich complex, [2+2] and [2+2+2] cyclomerization processes, C–H bond activation mediated by low-valent cobalt species, reaction patterns of dicobaltoctacarbonyl and diironnonacarbonyl towards phosphinoacethylenes, and complexes of transition metals with (ferrocenylethynyl)diphenylphosphane.
1 (Spectro)electrochemical studies of mixed-valent transition metal complexes. Theoretical background
The family of compounds called “mixed-valent compounds” originates from the observation of intense colors and electrical conductivity of inorganic systems found in the field of geology and also in the study of organometallic compounds.[B1] This term was introduced in 1958 by Klotz et al. for the intensively violet colored copper(I)/copper(II) complex of a Sulphur-containing succinic acid derivative,[B2] and is nowadays used, in general, for compounds containing redox centers in two distinct oxidation states. Such centers can be identical as for example Co(II) and Co(III) or different, for example, Fe(II) and Co(III) or Fe(III) and Co(II). The redox centers may be bridged or exist without bridging ligands. The occurrence of the electron transfer between the redox centers in different valence states gives those compounds unique properties. Those properties can be electrochemically and spectroscopically measured and quantified. One of the most prominent examples of a mixed-valent compound is the Creuz-Taube ion [(NH3)5Ru–
5+ [B1] pyrazine–Ru(NH3)5] presented in Figure B1. This ion became an archetype of the mixed-valent compounds and was followed by many modifications with varying bridging units (Figure B1).[B3–7]
19
5+ [B8] Figure B1: Creuz-Taube ion [(NH3)5Ru–pyrazine–Ru(NH3)5] and its modifications.
1.1 Mixed-valent compounds – classification
Theoretical work concerning mixed-valent compounds, which gave a basis for the classification and understanding of electronic process occurring in such compounds, was introduced in 1967[B9] almost simultaneously by Robin and Day[B10] as well as Allen and Hush.[B11–13] Robin and Day introduced the classification of the mixed-valent species on the basis of the extend/strength of the electronic interaction between the redox-active centers in different valence states.[B10] They divided these species into three classes:
Class I systems are characterized by no electronic interaction between the metal centers at distinct valence states. The properties of such systems consist of the sum of the properties of the individual redox centers of independent valence states. For example, in the spectra of a complex containing Co(II) and Co(III) metal centers, absorptions transition bands related to both Co(II) and Co(III) can be observed. This system therefore presents total electronic localization.[B9–14]
In class II species, there is a certain degree of electronic interaction between the different valence states and hence a certain degree of charge delocalization exists. However, metal ions at different oxidation states are still distinguishable. Electronic and optical properties of such compounds are a mixture of properties of the individual redox centers and of the molecule as one entity.[B9–14] Class II species show often semiconducting properties in the solid state.[B10]
A total charge delocalization is a characteristic to mixed-valent complexes of class III. The individual redox centers and their valence/oxidation state cannot be distinguished.[B9–14] The cause of the delocalization in the mixed-valent species of class III is the formation of new molecular orbital that contains the electrons of the two centers.[B8]
20 Therefore, this class of compounds is often referred as “average-valence” instead of “mixed-valence” species.[B10,14] The properties of such systems are no longer those of the individual, isolated redox centers.
Properties and features of compounds classified according to Robin and Day are summarized in Table B1.[B8]
Robin and Day introduced also the distinction between class III-A (the charge delocalization is limited to a polynuclear fragment of the solid) and class III-B (the charge is delocalized on the entire crystal unit, which is the source of conductivity).[B10] This subdivision is however related to ionic compounds and is not applicable to molecular systems.[B10,14]
Table B1: Characteristics of the three classes of mixed-valent species.[B8]
Optical Properties Electrical properties
Class I No intervalence charge-transfer Insulating band in the electronic spectrum. - Trapped electrons in ions of Color due to the isolated ions different symmetry
Class II Intevalence charge-transfer band Semiconducting in the Vis or NIR. (for a 1D, 2D or 3D solid) - Ions of almost identical symme- Deeper color than in isolated ions try
Class III Intervalence charge-transfer band Insulating in the Vis or NIR. - Delocalized electrons Strong color - Clusters - Equivalent and indistinguishable ions
1.2 Spectroelectrochemistry
UV-Vis/NIR-spectroscopy is a very useful tool to study mixed-valent systems because of the formation of a characteristic transition band called Intervalence Transfer (IT) or more often referred to as Inter-Valence-Charge-Transfer (IVCT) – appearing mostly in the NIR range of the spectrum (3000 – 10000 cm-1 ≈ 1000 – 3200 nm), as a result of optically induced electron transfer between two different states in the mixed-valent species.[B9–13] This band is for class II systems wide (≥ 2000 cm-1) and of low intensity (≤ 5000 L∙mol-
21 1∙cm-1).[B9–13] Class III is characterized by more intense absorption bands (≥ 5000 L∙mol- 1∙cm-1), which are much narrower than in class II (≤ 2000 cm-1).[B9–13] Appearance (or not appearance) of the IVCT band provides the means to distinguish between the three classes introduced by Robin and Day based on the degree of the charge delocalization.
Figure B2: Schematic representation of the potential energy surfaces for electron transfer in dinuclear, ligand bridged, mixed-valent complexes of Class I (a), Class II (b) and Class III (c).[B14] Figure taken with permission from ref. [B14].
Hush provided a tool for an analysis of the IVCT band shape based on the parameters that define the electron transfer barrier and therefore the extend of the charge localization or delocalization.[B11–13] Two parameters are of great importance: the
electronic coupling parameter (Hab) and the reorganization energy parameter (λ), which is defined as “the vertical difference between the free energies of the reactants and products for an electron transfer reaction with zero standard free energy change”.[B15] The physical meaning of reorganization energy parameter is that, it is “the energy required for bringing about the necessary structural readjustment at the individual redox sites of the dissolved molecule and the surrounding solvent shell, including the solvent dipoles and the counter ions”.[B16] The greater the λ value, the larger is the charge delocalization. When λ = 0, the two potential energy curves coincide (Figure B2 (a)). As an effect the IVCT band does not appear. If λ > 0 the IVCT band becomes visible. With an increase of the λ value, the energy of the IVCT band increases, and its position often shifts from NIR towards the visible range of the spectrum.[B8]
In case of a binuclear complex of class I (where there is no electronic coupling between
the redox centers and the charge is fully localized on one of the centers) is Hab = 0. If Hab ˃ 0 we deal with a system of class II or III.[B11–13] By weakly or moderately coupled systems (class II) electron transfer is subject to an energy barrier located between two minima on the adiabatic surface/energy surface. The electron is “valence trapped” in one minimum
22 but the probability of thermally or optically induced transfer from one to another is non-
[B11–13] zero. In such a case: 2Hab << λ (Figure B2 (b)). The value of the activation barrier
[B11–14] (Eth) is related to the parameters Hab and λ by equation (B1). Based on the Hush theory, the electronic coupling parameter Hab can be calculated by using experimental
[B11–14] data obtained from the IVCT absorption band (equation (B2)), where εmax is the intensity of the band at its maximum (extinction coefficient), νmax the energy of the transition, Δν1/2 bandwidth at half-hight and rab is the effective distance, which is the distance the electron need to pass during the IVCT transition.[B11–14] For this value the geometrical distance between the coupling centers from the single crystal X-ray diffraction data is often taken. This assures good results for weakly coupling systems. However, in systems with stronger coupling (see below), partial delocalization of the electron on the bridging orbitals connecting the coupling centers, leads to an
[B16–22] overestimated value of rab and therefore to a too low value of Hab.
= − + (B1)
∙ ∙ ∆ / = 2.06 ∙ (B2)
A class II system with stronger electronic coupling between the redox centers exhibits properties of both class II and class III. It is therefore called “borderline system” or “class II/III borderline”. Since the ligand orbitals and the metal orbitals interact, the single electron can be delocalized on the bridging unit and on the metal centers, therefore the extended delocalization causes that the compound can fall into the range of class III. The so called delocalization parameter (α) is useful in making distinction within this borderline system. This parameter can be calculated according to equation (B3).[B8] The upper limit for class II system is α = 0.25. A value smaller then this indicates that the electron is essentially trapped in one metal center.[B8]
= ( / ) (B3)
23 A very large value of Hab indicates strong electronic coupling and the system is of class III. The ground state potential energy surface exhibits a single minimum and the charge is
fully delocalized (Figure B2 (c)). With class III systems 2Hab >> λ, the thermal barrier
[B11–13] vanishes and the intermolecular electron transfer occurs. The calculation of the Hab parameter for class III compounds is straightforward. The value is half the energy of the electron transfer from the ground state to the excited state (B4).[B11–14]
= (B4)
Another useful classification method for the mixed-valent systems of class II, borderline class II/III and class III is provided by use of the so called classification parameter (Γ),
which can be calculated as in equations B5-6, from the transition energy (νmax) and
[B14,20,23] bandwidth at half-hight (Δν1/2).
= − ((∆ / )/((∆ / ) ) (B5)
/ / (∆ / ) = ( ∙ ∙ ) = ( ∙ ) (B6)
For weak coupling class II compounds the value of Γ is in the range 0 < Γ < 0.1. The moderately coupling class systems are in the range 0.1 < Γ < 0.5. The value of Γ ≈ 0.5 indicates borderline class II/III compounds and Γ > 0.5 class III.[B14,20,23]
Electron transfer processes in the mixed-valent species beside the IVCT forms also other absorption bands. Based on the theory of Hush (which described systems in two states), Creutz, Newton and Sutin developed an extended model, taking into account more excited states. This model describes also appearance of ligand-to-metal-charge-transfer (LMCT) and metal-to-ligand-charge-transfer (MLCT) transition bands in the systems of class II and III.[B14,23–25]
24 1.3 Electrochemistry
Cyclic voltammetry (CV) and square-wave voltammetry (SWV) are widely used in electrochemical studies providing an indication of an electronic coupling (electronic communication) between two metal redox centers in an organometallic and metal-organic compound. In a homobinuclear compound (M1 = M2) with a strong electronic coupling between the metal centers connected with a bridging unit, a reversible redox wave will be formed for each of the redox centers. An electrochemically reversible redox process is defined by Randles-Sevčik through an equation showing the proportionality between a
[B26] current density (ip) and root of the potential scan rate (sweep rate) (v) (equation B7). The current density depends on the concentration of the analyte (C) and diffusion rate (D) of the oxidized and reduced species. Because the surface of the electrode (A) is a constant value, it is experimentally possible to determine the number of electrons (n) involved in the redox process by an applied potential scan rate (v).[B27,28]
/ / / = . ∙ ∙ ∙ ∙ ∙ ∙ (B7)
For a reversible one-electron redox process, ΔEp (which is the potential difference between the oxidations peak (anodic wave, Epa) and the reduction peak (cathodic wave,
Epc), (equation B8 and Figure B3)) accepts by equal diffusion rate of the oxidized and reduced species within standard conditions (ΔEp°' for standard conditions) a limiting value of 59 mV. This variable is diffusion controlled and therefore temperature dependent. ΔEp decreases with the decreasing temperature (for example it is only 44 mV at –50 °C).[B26]
= − (B8)
25 30 Epa
20 Epa
10 A]
E E 0 1 E2 Current [ Current -10
-20 Epc
Epc -30 -500 -400 -300 -200 -100 0 100 200 300 400 + Potential [mV] vs FcH/FcH
Figure B3: Representation of a cyclic voltammogram for a reversible redox process (not published work).
ΔEp value for a reversible redox processes is not dependent on the cyclic voltammetry scan rate. However, quasireversible and especially irreversible redox processes are on the
[B28,29] scan rate dependent. The ΔEp becomes larger in comparison to the reversible process, due to the delay of the mass or charge transport through the double layer at the electrode surface (Figure B4). This effect can be reduced by use of appropriate compensation methods.[B27,30]
a) b) c)
Figure B4: Schematic representation of a theoretic cyclic voltammogram (CV) for reversible a), quasireversible b) and irreversible c) redox process.[B28] Figure taken from ref. [B28] with permission from Copyright Wiley-VCH Verlag GmbH & Co. KGaA.
A potential of a redox event (Ex or Ex°' for standard conditions, where x = 1, 2, …) can be calculated according to equation B9.
= ( + )/ (B9)
26 The separation of two redox waves, which is the potential difference ΔE (ΔE°' for standard conditions), known and commonly used in the literature as “half-wave potential splitting” (ΔE1/2) between two reversible redox events E1 and E2 (Figure B3) was in the past used as an indicator of the communication (electronic coupling) between the redox centers,[B20,31] which was found to be not in every case correct.[B16] A very small value of ΔE°' supposed to indicate that there is no interaction between the metal centers (class I). Small value of ΔE°' indicated that the studied compound belongs to class II, and larger value was interpreted as a presence of class III mixed-valent system. However, as it was pointed out by Winter and discussed in his review article, growing number of experimental data reveal that there is no unequivocal relationship between ΔE°' and
[B16] Hab. Although in a great number of examples the ΔE°' (ΔE1/2) value correlate in a good way with the degree of electronic coupling,[B18,32,33] there is also a significant number of examples of mixed valent systems with small value of ΔE°' and strong electronic coupling,[B34–39] or the opposite, compounds with no electronic coupling despite high value of redox potential splitting ΔE°'.[B21,40–42]
The nature of the bridging unit connecting the interacting redox sites has a great influence on correlation (or no correlation) between the ΔE°' and electronic coupling. In some cases the fully π-conjugated bridge such as arylene, alkenyl, or ethynyl can have overlapping orbitals with those of the bridged redox active sites and actively participate in the redox process.[B16] However, a connecting bridge can also have no orbital interactions with the redox-active sites and serves only as an element holding those sites in proximity. In the first case, despite small ΔE°' value, large electronic coupling to each other can be expected. In the other situation, the opposite can be expected. The redox splitting ΔE°' is mainly caused by electrostatic repulsion between active redox sites.[B16]
Reasonable comparison and correlation between ΔE°' and Hab can take place, when measurements of different compounds are performed in the same solvent-electrolyte system, because the individual redox potentials and therefore ΔE°', depend strongly on electrostatic interactions between the charged sites, which is influenced by the ion pairing ability of the electrolyte with the charged sites, as well as structural distortion occurring during the redox process.[B16,20,43–47] The separation of two redox events depends on the coordination ability of the counter ion of the applied electrolytes. Due to this coordination an insulation of them against each other occurs, whereby the stabilizing repulsive electrostatic interaction between oxidized sites is diminished and hence the
27 thermodynamic stability of the mixed-valent state is reduced. As a result, weak or no redox splitting is observed.[B45,48,49] It is advantageous to use an electrolyte with
– [B(C6F5)4] as an anion, leading to an increase of the observed splitting of the redox events
– – – because in opposite to the commonly used counter ions such as [PF6] , [BF4] or [ClO4] ,
– [B45,48,49] the [B(C6F5)4] ion is weakly coordinating anion.
It must be emphasized, that ΔE°' value cannot be applied to directly measure the extend
of the electronic coupling (Hab), and therefore cannot be conclusively used to distinguish between the classes of the mixed-valent compounds.[B16,20,31] It may give only a qualitative indication of the ground-state delocalization in the mixed valent state and must be evaluated and confirmed by means of spectroscopic measurements and analysis of the IVCT bands (see Chapter 1.2).
It is worthy to notice that the value of ΔE°' is proportional to the thermodynamic stability of the mixed-valent species in a given solvent and electrolyte. It can be therefore used to evaluate if an isolation of the mixed-valent species is possible.[B20,50–52]
2 (Di)ferrocenylalkynes – synthesis and reactions
The interest in ferrocenyl-substituted acetylene, (poly)alkynes and their derivatives started in 1970 with the discovery of the mixed-valent properties of biferrocene (Fe(II)Fe(III)) picrate (1) by Cowan and his research group (Figure B5).[B53] This compound was obtained by the oxidation of diferrocene with excess of benzoquinone in the presence of picric acid.[B53] The biferrocene (Fe(II)Fe(III)) picrate, together with the synthesized and characterized Creutz-Taube ion[B1] (Figure B1) is one of the first studied mixed-valent compounds. These discoveries were followed by a series of investigations and the synthesis of derivatives such as bis(fulvalene)diiron (2),[B54] diferrocenylacetylene (3),[B55] [2,2]ferrocenophane-1,13-diyne (4)[B55] and diferrocenylbutadiyne (5)[B55] (Figure B5), whereby the relationship between the properties of the electron transfer process and the geometry of the mixed-valent compounds or the distance between the redox-active centers were noticed and analyzed.[B54,55]
28
(1)+ (3)+ (5)+
(2)+ (4)+
Figure B5: Diferrocene and its mixed-valent derivatives (1)+,[53] (2)+,[54] (3)+,[55] (4)+,[55] (5)+.[55]
The most well-known ferrocenylalkynes beside 1,4-diferrocenylbutadiyne (Fc–C≡C–
5 5 C≡C–Fc, (Fc = Fe(η -C5H4)(η -C5H5)) are ethynylferrocene, diferrocenylacetylene and their derivatives. They show similar reaction patterns toward metal carbonyls.[B56–70]
This section discusses the synthesis and research regarding the reaction of 1,4- diferrocenylbutadiyne. The synthesis and properties of some other related ferrocenyl- substituted alkynes will also be given as examples.
2.1 1,4-Diferrocenylbutadiyne
1,4-Diferrocenylbutadiyne was utilized in this research study as a major reagent to obtain extended, cyclic, perferrocenylated compounds. Therefore, a short description of the synthesis methods and former application of this compound as a reagent in the chemical synthesis is given here.
1,4-Diferrocenylbutadiyne is accessible by oxidative homo-coupling of etynyl- ferrocene[B71] in a reaction procedure catalyzed by copper (II) acetate in ether/methanol/pyridine solutions either by reflux under nitrogen or oxygen flush at ambient temperature (38 and 41 % yield).[B72] In the same way 1,8-diferrocenyl- octatetrayne was also synthesized by coupling butadiynylferrocene.[B72] A similar but high yield synthesis (89 %) of the 1,4-diferrocenylbutadiyne was described by Rodrigues et al.[B73] Also in this procedure oxidative homocoupling of ethynylferrocene was utilized.
29 However, in this case the reaction was conducted in air, in a solution of pyridine and in presence of copper(I) chloride (Figure B6).
Figure B6: Synthesis of 1,4-diferrocenylbutadiyne by oxidative homocoupling of etynylferrocene catalyzed t [B73] by CuCl. (i) Ph3P=CHCl; (ii) KO Bu; (iii) Cu2Cl2, O2, pyridine.
Recently, a synthesis method in supercritical (sc) carbon dioxide (scCO2) was reported, where a range of 1,3-diynes was accessible from terminal alkynes by copper(I) catalyzed homocoupling without the use of any organic solvents.[B74] DBU (1,8- diazabicyclo[5.4.0]undec-7-ene) was acting as the base and was the key additive for the homocoupling reactions. In this way 1,4-diferrocenylbutadiyne was obtained in 76 % yield.[B74] Another synthesis method, which derives from an area of Green Chemistry, is the solvent free homocoupling by use of trimethylamine as base (3 mol%) and copper(II) chloride (3 mol%) as the catalyst at 60 °C in air. 1,4-Diferrocenylbutadiyne was obtained in 99 % yield.[B75]
One of the main research directions concerning 1,4-diferrocenylbutadiyne is the investigation of its coordination behavior toward transition metal-carbonyls and metal- carbonyl clusters.
An early study of the reaction of ferrocenyl substituted alkynes with metal carbonyls and clusters goes back to the research group of Koridze et al in the 1990s. They
investigated and reported the reaction of 1,4-diferrocenylbutadiyne with Ru3(CO)12 in boiling hexane, which resulted in a mixture of organometallic diruthenium compounds, where cyclization and coordination to the formed ethylenic/ethenyl bonds occurred (Figure B7).[B76]
6 7 8
30
9 10 11
5 Figure B7: Reaction of 1,4-diferrocenylbutadiyne with Ru3(CO)12 in hexane to give 6 – 11 (Fc = Fe(η - 5 [B76] C5H4)(η -C5H5)).
The obtained products can be subdivided into two groups: heterocyclic five-membered ruthenium containing rings (6 – 8) and binuclear complexes with the Ru2(CO)6 unit coordinated by a C5O moiety (9 – 11). These compounds exist as three isomers, formed by “head-to-head”, “head-to-tail” or “tail-to-tail” dimerization of two diyne molecules.
The same set of products was obtained by Mathur et al.[B77] However, modified reaction condition (–10 °C, hexane) allowed the formation of 12, (which is the product of the coordination of a single acetylenic bond to the Ru3(CO)10 cluster) and 13 (compound similar to 8 obtained by Koridze but with an additional CO bridge between the ruthenium atoms) (Figure B8).
12 13
5 5 Figure B8: Reaktion of Ru3(CO)12 with 1,4-diferrocenylbutadiyne to give 12 and 13 (Fc = Fe(η -C5H4)(η - [B77] C5H5)).
A similar reaction pattern of 1,4-diferrocenylbutadiyne was observed by Adams et al. by investigating its reaction with the triosmiumcarbonyl cluster Os3(CO)10(NCMe)2 at 97 °C in hexane in which the compound 14 (9 %) was obtained (Figure B9).[B78] However, the
° reaction with Os3(CO)11(NCMe) at lower temperature (67 C) resulted in the formation of 15 (31 %) and 16 (18 %) (Figure B9).[B78,79] Cluster 16 could be obtained in much higher
31 ° [B78] yield (96 %) from the reaction with Os3(CO)10(NCMe)2 at 67 C. In 15 a trinuclear, linear osmium unit attaches to the alkynide triple bonds of Fc–C≡C–C≡C–Fc in a di-μ-‖ coordination mode. In this mode an alkynyl group donates to the metal atoms two electrons by utilizing one of its two π-bonds only.[B78] Therefore, 15 received four electrons from the butadiyne moiety. In case of 16 one of the butadiyne triple bond is coordinated to the tri-nuclear osmium moiety, which takes a shape of triangle. This compound converts to cluster 17 at 97 °C (Figure B9).
15
16
14
17
5 5 [B78] Figure B9: Os3 clusters 14 – 17 (Fc = Fe(η -C5H4)(η -C5H5)).
A simple coordination of one or both alkynyl groups to metal-carbonyl was presented in 2001 by the research group of Draper.[B80] They reported a series of such coordination
products with dicobaltoctacarbonyl, by π-addition of C≡C bond to Co2(CO)6 fragment to form the so called metallatetrahedranes (18 – 20), possessing approximately tetrahedral (μ-alkyne)dicobalt moieties (Figure B10).[B80] Similar results were obtained by Suo et al in 2004.[B81]
32 (CO)3 Co Fc C C Fc Mo Cp 18 19 20
5 5 Figure B10: Coordination of C≡C bonds to metal carbonyl fragments, 18 – 20 (Fc = Fe(η -C5H4)(η - [B80] C5H5)).
Compound 20 was obtained by replacing one of the Co(CO)3 groups with isolobal
[B80] MoCp(CO)2. Bruce et al. reported the synthesis of 21 (37 %) and 22 (45 %) which are accessible in the reaction of 1,4-diferrocenylbutadiyne with Ru3(CO)10(NCMe)2 or Ru3(μ-
[B82] ° dppm)(CO)10. Heating Ru3(μ-dppm)(CO)10 and FcC≡C–C≡CFc in benzene up to 80 C resulted in the formation of 23 (8 %), where two molecules of FcC≡C–C≡CFc are involved (Figure B11).[B82]
A different reaction behavior of 1,4-diferrocenylbutadiyne toward iron pentacarbonyl is observed in a photochemical reaction in methanol by continuous bubbling CO through the reaction solution at 0 °C. This reaction provided a group of cumulene-based complexes (24 – 26). The three compounds 24 – 26 are isomers in relation to the position of the terminal ferrocenyl groups. The structures of the products are depicted in Figure B12.[B83] Compound 27 was also formed in the same reaction, however, it differs from the other products in the way that no Fe–Fe units were formed but only Fe(CO)4 moieties inserted to the ferrocenyl substituted diene via carbonyl bridges.
33 21
22 23
Figure B11: Reaction of FcC≡C–C≡CFc with Ru3(CO)10(NCMe)2 or Ru3(μ-dppm)(CO)10 to give 21 – 23 (Fc = 5 5 [B82] Fe(η -C5H4)(η -C5H5)).
27
24 25 26 27
5 5 [B83] Figure B12: Reaction of FcC≡C–C≡CFc with Fe(CO)5 to give 24 – 27 (Fc = Fe(η -C5H4)(η -C5H5)).
34 2.2 Other (poly)ferrocenyl substituted alkyne derivatives
Besides diferrocenylacetylene and 1,4-diferrocenylbutadiyne, higher homologes of
[B84] these compounds, such as 1,6-bis(ferrocenyl)-1,3,5-hexatriyne (Fc(C≡C)3Fc) (31), 1,8-
[B85] bis(ferrocenyl)-1,3,5,7-octatetrayne (Fc(C≡C)4Fc) (32), 1,12-bis(ferrocenyl)-
[B86] 1,3,5,7,9,11-dodecahexayne (Fc(C≡C)6Fc) (33) and their complexes with osmium carbonyls[B85,86] or cobalt carbonyls[B86] are also known. The products 34 – 37 of the
[B85] reaction of 32 with Os3(CO)11(NCMe) are depicted in Figure B13. The synthesis procedure of 33 from 28 via 29, 30 and its reaction with Os3(CO)11(NCMe) or Co2(CO)8 to give 38 and 39 are shown in Figure B14.[B86]
32
34 35 36
37
5 5 [B85] Figure B13: Reactions of Fc(C≡C)4Fc with Os3(CO)11(NCMe) to give 34 – 37 (Fc = Fe(η -C5H4)(η -C5H5)).
35 30 28 29
30 33
38
33
39
Figure B14: Synthesis and reaction chemistry of 1,12-bis(ferrocenyl)-1,3,5,7,9,11-dodecahexayne 33 (Fc = 5 5 [B86] Fe(η -C5H4)(η -C5H5)).
Butadiyne with mixed substituents, 1-ferrocenyl-4-phenyl-butadiyne, was applied by Mathur et al. to obtain a series of mixed-substituted cyclopentadienons and other derivatives containing iron-carbonyl moieties (40 – 45) by the photochemical reaction
with Fe(CO)5 in hexane. The same photochemical reaction performed in presence of CO gave additionally 40 – 43 and 46 (Figure B15).[B87]
36 40 – 43
46
40 41: R1, R4 = PhC≡C; R2, R3 = Fc 44: R1, R4 = Fc; R2, R3 = PhC≡C
42: R2, R4 = PhC≡C; R1, R3 = Fc 45: R1, R3 = Fc; R2, R4 = PhC≡C
43: R1 = PhC≡C; R2, = Fc; R3 = Ph; R4 = FcC≡C
[B87] Figure B15: Photochemical reactions of 1-ferrocenyl-4-phenyl-butadiyne with Fe(CO)5 to give 40 – 46.
3 Dicarbonylcyclopentadienylcobalt – [2+2] and [2+2+2] cyclo- addition reactions
Multi-substituted ferrocenyl-based cyclic and heterocyclic compounds can be considered as sterically crowded species. Such systems provide an excellent scaffold for the study of electronic interactions between the redox-active centers in relation to the distance between them, the nature of the bridging ligands, the extend of conjugation, their relative orientation to each other and to other ligands present in the molecule.[B20,55,88–92]
Negishi[B93] or Sonogashira[B94,95] C–C cross coupling reactions, allows to prepare such compounds. In this respect, ferrocenylated compounds as Vollhardt’s hexaferrocenylbenzene,[B96] Astruc’s penta- and hexa(ferrocenylethynyl) benzenes[B97,98] and mixed-ferrocenyl and ferrocenyletynyl substituted benzenes[B43] prepared in our
5 [B99] group were accessible. Also half-sandwich complexes like Mn(η -Fc5C5)(CO)3 as well
c as heterocyclic five-membered Fc-substituted rings of the general formula C4Fc4E (E = S,
5 [B17,19,40,61,100–104] O, NMe, NPh, Zr(η -Fc5C5)2) and 3,3’,4,4’,5,5’-hexaferrocenyl-2,2’bithio- phene[B105] are accessible in this way.
There is however another, less laborious and more efficient way to diverse substituted cyclic compounds, namely by utilizing the ability of carbon – carbon triple bond to
37 undergo cyclomerization processes.[B106-126] The following description of the possible mechanisms can offer a better understanding of the results discussed in Chapters C and D.
3.1 [2+2] and [2+2+2] cycloaddition – cyclobutadiene, cyclopentadienone, benzene and pyridine based systems
Cyclomerization reactions such as [2+2] or [2+2+2] cycloadditions, are an efficient alternative way to obtain cyclic compounds, such as benzene, 1,3-cyclohexadiene and their derivatives as well as heterocyclic compounds such as pyridines, pyridones, pyrans and pyrimidine diones.[B106] These reactions are catalyzed by a whole range of transition metal complexes.[B106–108] Particularly, in the synthesis of substituted 4-, 5- and 6- membered rings, are cyclization reactions catalyzed by dicarbonyl-cyclopentadienycobalt
5 Co(η -C5H5)(CO)2 (= CoCp(CO)2). This reaction was first studied in 1961 by Nakamura and Hagihara[B109] and further explored in the following years by Rausch and Genetti.[B110–114] Dicarbonylcyclopentadienylcobalt and its cyclopentadienyl substituted derivatives are accessible from the respective cyclopentadienes in the reaction with dicobalt- octacarbonyl.[B111,112]
In this respect, several ferrocenyl-substituted cyclobutadienes 47,[B69,88] 48,[B69,88] 49,[B66,69,88] (Figure B16a) and benzenes 50,[B115] 51,[B115] 52,[B58] 53[B58] (Figure B16b) as well as pyridine derivatives 54 – 57,[B116] 62 – 64,[B117] 66[B117] (Figure B16c,d) were accessible. Compounds 58 – 61,[B116] 65, 67 – 69[B117] are theoretically possible but were not detected among the products of the reaction.[B116,117]
a) 47 48 49
b) 50 51 52 53
38 c) 54, 55 56, 57 58, 59 60, 61
d) 62, 63 64, 65 66, 67 68, 69
Figure B16: Ferrocenyl-substituted cyclobutadienes 47,[B69,88] 48,[B69,88] 49,[B66,69,88] (a), benzenes 50,[B115] 51,[B115] 52,[B58] 53[B58] (b), and ferrocenyl-, ferrocenylethynyl-substituted pyridine derivatives 54 – 61,[B116] 62 – 69,[B117] (c,d).
Other substituted benzenes,[B114] cyclobutadienes,[B114,118,119] cyclopentadienons,[B114] and extended cyclobutadiene derivatives such as 70,[B114] 71,[B118] 72,[B118] 73 – 75[B118,119] and 76[B119] were also formed via the cyclomerization of 1,4-diphenylbutadiyne or counterparts with other substituents (Figure B17). They were prepared by using
[B114,118,119] CoCp(CO)2, and CoCp(PPh3)2 or CoCp(cod). Known are also cyclopentadienone and benzoquinone derivatives with iron-carbonyl moieties, containing mixed ferrocenyl and phenyl substituents. However, they were obtained by the photochemical reaction of
[B87] substituted butadiynes with Fe(CO)5 (Figure B15).
70
39 71: R = CO2Me 72: R = CO2Me
73 – 75: R = H or CO2Me 76: R = H
Figure B17: Formation of diverse cycloaddition products 70,[B114] 71,[B118] 72,[B118] 73 – 75[B118,119] and 76.[B119]
3.2 Mechanism of [2+2] and [2+2+2] cycloaddition/cyclization and [2+2] cycloaddition/cyclization with CO insertion mediated by CoCp(CO)2
The mechanism of cycloadditions reaction catalyzed by CoCp(CO)2 was studied by several research groups.[B107,111,117–126] The proposed mechanism leading to the respective products and isomers of the competitive [2+2], [2+2+2] and [2+2] cycloadditions with CO insertion is presented on the example of the 1,4-diferrocenylbutadiyn (Figure B18).[B107,111,117–126]
The substitution of one or two CO ligands in CoCp(CO)2 with alkynes occurs first, followed by the oxidative addition to cobalt.[B111,121–124] At this point, intermediates Ia,b or IIa,b are formed (Figure B18), which may be in equilibrium with each other by elimination or addition of CO (Figure B18).[B107,120,121,124–126] Intermediates Ia,b/IIa,b can give the products shown in Figure B18.
Compound 1 (Figure B18) is formed from the intermediate Ia,b, via reductive elimination and complexation to the CpCo moiety. Depending on the orientation of the FcC≡C groups, isomers 1a or 1b are formed (Figure B18).[B111,121–124]
40 Co Co OC CO OC CO
R1 R2 - CO R1 R2 - CO
R1 R1
R R R1 R R1 R2 R1 R2 1 2 R R Co 1 R2 R1 R R1 1 2 Co Co 1 Co Co Co - CO OC OC OC R2 - CO OC R2 R2 R1 R2 R2 R1 R R2 2 R2 R1 R2
R1 R1 Co R - CO Co Co - CO R2 1 Co R OC OC R1 1 R R + CO 2 1 + CO R2 R2 R1 R2 R R2 2 R1 R Intermediate Ia 2 Intermediate Ib Intermediate IIa Intermediate IIb R1 R2 - CO - CO R1 R2
R R2 Co R1 R2 Co R1 R1 2 R1 Co R1 Co O Co R1 O Co R1
R1 R2 R1 R2 R2 R2 R R 1 2 R R R2 2 1 R2 R R2 R1 1 R2 R1 R2 1a Intermediate IIIa Intermediate IVa Intermediate IVb Intermediate IIIb 1b
R R 2 R 2 O R1 O 1 R1 R1 Co Co R1 R1
R2 R2 R1 R2 R2 R2 R1 R2 R R 1 R1 R2 2
3a 2a 2b 3b
O R2 Co
R2 R1
R : Fc 1 R1 R2: Fc 2c
Figure B18: Schematic representation of the competitive formation of possible products and isomers of [2+2] cycloaddition (1a,b), [2+2+2] cycloaddition (2a–c) and [2+2] cycloaddition with CO insertion (3a,b). [B107,111,117–126] R1 = Fc, R2 = FcC≡C in the reaction of FcC≡C–C≡CFc with CoCp(CO)2.
Compound 2 can be formed by a competitive reaction from intermediate Ia,b, by insertion of CO via the intermediate IIa,b and the Intermediate IVa,b (Figure B18) Reductive elimination and complexation leads to the formation of 2. Three isomers (2a–c) are possible, depending on the orientation of the substituents (Figure B18).[B107,111,121,124,125]
41 Coordination of an additional alkyne to Ia,b or alternatively ligand exchange at the intermediate IIa,b followed by oxidative addition, forms IIIa,b (Figure B18) from which via reductive elimination 3a,b are formed.
Very interesting in terms of the synthesis of polyferrocenylated chain complexes (which can be considered oligomers of complex type 1 (Figure B18)), is the formation of dimers 70, 73 – 75 and trimer 76 (Figure B17). These species are accessible by a further cyclization reaction of 1a,b, if at least one more alkynide functionality is present in the molecule. Formation of these compounds by simultaneous reaction of several alkynes (as
[B118] FcC≡C–C≡CFc), with two molecules of CoCp(CO)2 was suggested by Singh et al. However, they proposed also another mechanism, which was found to be more probable. The mechanism is presented in Figure B19.[B118]
Ph Ph Co + Ph C C Ph
C Ph C Ph
Ph Ph Co 2
C Ph C Ph
Figure B19: Schematic representation of the formation of dimerized and trimerized cyclomerization products.[B118]
4 Chelation-assisted C–H bond activation mediated by cobalt species
The goal of this chapter is to offer a better understanding of the results discussed in Chapter D of this dissertation.
The relative unreactive C–H bond is known to be selectively functionalized via coordination assisted by transition metal complexes.[B127] Murai et al achieved a selective
42 and efficient way of ruthenium-catalyzed addition of aromatic carbon-hydrogen bonds to the double bond of olefins.[B127] This process is an important and critical step in the conversion of aromatic hydrocarbons to other organic compounds. A broad variety of C–C and C–heteroatom bond formations can be accessed in this way. Most often applied, but expensive, are ruthenium-, rhodium- and palladium-based catalysts.[B128–131] The use of cobalt catalysts for chelation-assisted C–H bond cleavage was initiated by Murahashi,[B132] by applying dicobaltoctacarbonyl.[B132] High- and low-valent cobalt (beside other first-row metals such as manganese, iron, nickel and copper) provide today an alternative low cost route to achieve the above mentioned goals.[B133–136]
Mechanistic studies of the C–H bond activation in aromatics and addition to alkynes by means of deuterium-labeling experiments revealed that this process follow several steps: (1) precoordination of the alkyne to the catalytic active center, (2) chelating-assisted oxidative addition of the C–H bond and formation of a cobaltacycle intermediate, (3) migratory insertion of the alkyne to give an organo-cobalt species, and (4) reductive elimination with formation of the product and regeneration of the catalyst.[B137–144] An alternative possible route was proposed, where the oxidative addition of the C–H bond to the cobalt catalyst and formation of the cobaltacycle intermediate occurs first, followed by coordination of the alkyne. Alkyne insertion and reductive elimination close the catalytic cycle.[B138,139] The rate-determining step was found to be the chelation-assisted insertion of the C–H bond.[B138–140] A schematic cycle of both alternative mechanisms of such process assisted by low-valent cobalt catalyst, proposed by Yoshikai and co-workers, is provided in Figure B20 on the example of aromatic C–H bond cleavage and insertion to
[B138] alkynes. Low-valent cobalt species were generated from CoBr2 in the reaction with a triarylphoshin ligand P(3-ClC6H4)3, a Grignard reagent (neopentylmagnesium bromide) and pyridine.[B138]
43 [Co]: low-valent cobalt species
Figure B20: Example of two alternative catalytic cycles of the chelation-assisted aromatic C–H bond activation and alkyne addition mediated by low-valent cobalt species.[B138] Figure taken with permission from ref. [B138].
5 Phosphinoalkynes and their reaction with iron and cobalt carbonyls
The aim of this chapter is to present the reaction patterns of phosphinoalkynes toward
iron and cobalt carbonyls. A mechanism of the P–C(sp) bond cleavage in phosphinoalkynes occurring during a specific type of reaction,[B145–149] will also be presented. This section is a brief introduction to the results discussed in Chapter E of this dissertation.
The rich and diverse reaction chemistry of phosphinoalkynes of the general formula
PR’3-n(C≡CR)n (R = R’, R ≠ R’; R, R’ = single bonded organic group; n = 1, 2, 3) towards different metal carbonyls is the result of their ability to coordinate to more than one metal
44 center at the same time via different binding modes, such as μ symmetrical μ2, edge-
2 2 2 [B147,150–152] bridging μ2-η or face-bridging μ3-η or μ4-η (Figure B21). Additionally, the phosphinoalkynes can act as two-electron or four electron donor ligands and can coordinate either by the phosphorus atom, by the alkynyl group or by both. The additional versatility of phosphinoalkynes as ligands arises from the relative facile P–C(sp) bond cleavage.[B145–149]
(a) (b) (c) (d) (e) (f) (g)
Figure B21: Diverse binding modes of acetylenes in coordination to transition metals: μ1 (a), μ2 (b), μ3 (c), 2 2 3 2 [B147,150–152] μ2-η (d), μ3-η (e), μ4-η (f), μ4-η (g).
A common type of compounds formed in the reaction of phosphinoalkynes with iron[B145–148,153–156] or cobalt carbonyls[B153,157–165] are compounds containing a mono-, di- or trinuclear metal-carbonyl core.[B147,149–151,157,165]
The products of the reaction of PPh2C≡CPh with iron-carbonyl compounds are the mononuclear complexes Fe(CO)4(PPh2C≡CPh) (77) and Fe(CO)3(PPh2C≡CPh)2 (78).[B146,155] These compounds can be obtained by the reaction of diironnonacarbonyl and (phenylethynyl)diphenylphosphane.[B146,155]
77 78
2 Binuclear compounds are also known. One example is M2(CO)6(μ2-η -C≡CR)(µ2-PPh2) (M = Fe, Ru, Os; R = organic ligand), which possesses a direct Fe–Fe bond (79). The dimetalhexacarbonyl moieties are bridged by diphenylphosphido and alkynyl functionalities, whereby the alkynyl bridge is functioning as one-electron donor to one iron atom via σ bond and as a two-electron donor to the other iron atom via a π bond.[B145–
45 B148,153,155] A further example of a dinuclear iron compound is Fe2(CO)6(RC≡CPPh2)2 (80).[B154,155]
79 80
Trinuclear phosphinoalkyne based iron complexes (81 – 88) were reported by Mathur
[B156] et al. These compounds were obtained by treatment of Fe3E2(CO)9 (E = Se, Te) with
(RC≡C)3P, (R = Fc, Ph) in a thf solution at room temperature in presence of Me3NO⋅2H2O (Figure B22).[B156]
81: E = Se; R = Fc, 83: E = Se; R = Fc 87: E = Se; R = Fc 82: E = Se; R = Ph 84: E = Se; R = Ph 88: E = Se; R = Ph 85: E = Te; R = Fc 86: E = Te; R = Ph
[B156] Figure B22: Reactions of Fe3E2(CO)9 with tris(phenyl/ferrocenylethynyl)phosphane.
Dicobaltoctacarbonyl Co2(CO)8 forms complexes with phosphinoalkynes usually by
[B153,157–161,163–172] coordinating to the acetylic triple bond to give Co2C2 tetrahedran. The characteristic coordination modes for cobaltoctacarbonyl are shown in structures 89 and 90. However, by the ratio of 2:1 of the cobalt-carbonyl reagent in relation to the phosphinoalkyne, the coordination by the phosphorus atom is also observed (91,
46 [B157,166] 2 92). A structurally interesting species is {(R’C≡C)2P((η -C≡CR)Co2(CO)5)}2 (R = R’;
[B157,162] R ≠ R’), which is available by the reaction of P(C≡CR)3 with Co2(CO)8 (93).
(CO)3 R' R R R P (OC)4Co Co R C C 2 C C P C C R2 (OC)3Co Co(CO)3 (OC)2Co Co(CO)3 (OC)3Co Co(CO)3
89 90 91
R' R (CO)2 R2 R2 Ph C C R' (OC)3Co Co P P C C C C (OC)3Co Co(CO)2 C C P Co Co(CO) (OC) Co Co(CO) Ph R 3 3 3 2 (CO)2
92 93
An few examples of mixed polynuclear complexes containing both cobalt- and iron- carbonyl moieties are given in Figure B23.[B153]
Ph2 (OC)4Fe P C C Ph
Co(CO)2P(OMe)3 (MeO)3P(OC)2Co
(ii) 96 (ii)
Ph2 (i) Ph2 (ii) Ph2 (OC) Fe P (OC) Fe P (OC) Fe P 4 4 4 Ph C C C Ph C C C Co(CO)3 Co(CO)2P(OMe)3 Ph (OC)3Co (OC)3Co
77 94 (iii) 95
Ph Ph C C (iv) C C Fe(CO) Ph3P(OC)Co 3 (OC)2Co Fe(CO)3 Ph P 2 Co(CO)P(OMe)3 Ph2P Co(CO)P(OMe)3
98 97
Figure B23: Examples of polynuclear mixed Co-Fe clusters 94 – 98. (i) Co2(CO)8, CH2Cl2, rt, 12 h; (ii) [B153] P(OMe)3, hexane, heating, 1.5 h; (iii) toluene, heating, 24 h; (iv) PPh3, hexane, 24 h.
47 Known are also star-like compounds of type 1,3,5-(M(CO)5(Ph2P((2-
C≡C)Co2(CO)6)3C6H3) (M = Mo, W) (99, 100). These compounds were obtained from
[B173] 1,3,5-(Ph2PC≡C)3C6H3 in reaction with M(CO)5(thf) and hν.
99: M = Mo, 100: M = W
5.1 Mechanism of the P–C(sp) bond cleavage in phosphinoalkynes
A feature in the reaction of phosphinoalkynes with di- and trinuclear metalcarbonyls is
° the facile (50 – 80 C) cleavage of the P–C(sp) bond between the phosphine and the acetyl carbon atom.[B145–149,153,155] The mechanism of the formation of the phosphido- and σ,π- acetylido-bridged diironcarbonyl complexes was investigated by Carty and co- workers.[B146–148] The proposed mechanism starts with the coordination of the phosphidoalkynyl to diironnonacarbonyl via the formation of a phosphorus dative bond.
In the next step the second Fe2(CO)9 molecule is involved and coordination of the C≡C
triple bond to Fe(CO)4 occurs, followed by the P–Csp bond cleavage. Formation of diphenylphosphido and σ,π-acetylid bridges with loss of two CO molecules accomplishes this process (Figure B24).[B146–148]
2 Figure B24: Mechanism of the formation of M2(CO)6(μ2-η -C≡CR)(µ2-PPh2) (M = Fe, Ru, Os; R = organic ligand).[B146,147]
48
The reaction chemistry of phosphinoalkynes with trinuclear metalcarbonyls, such as
t i [B148,149] Ru3(CO)11(PPh2(C≡CR)), (R = Bu, Pr) follows a different pathway (Figure B25).
(CO) (CO) (CO) 4 4 4 Ru Ru Ru
(OC)3Ru Ru(CO)3 (OC)4Ru Ru(CO)3 (OC)3Ru Ru(CO)3 - CO PPh2 PPh2 PPh2 Ph Ph Ph
- Ru(CO)4 - CO
(CO)3 Ph2 Ru P Ph (CO)3 Ru (OC)3Ru Ru(CO)3 PPh2 Ru (CO) 3 Ph
Figure B25: Proposed mechanism for the formation of Ru2(CO)6(µ-PPh2)(µ,π-C≡CPh) and t i [B148,149] Ru3(CO)11(PPh2(C≡CR)), (R = Bu, Pr).
The homobimetallic compound Fe2(CO)6(µ-PPh2)(µ,π-C≡CFc) shows interesting dynamic processes as depicted in Figure B26.[B148]
Figure B26: Mechanism of the dynamic σ,π-acetylide interchange in compound Fe2(CO)6(µ-PPh2)(µ,π- C≡CFc).[B148]
49 6 Complexes setup by (ferrocenylethynyl)diphenylphosphane
(Ferrocenylethynyl)diphenylphosphane can act as a stable, reversible redox-active ligand in diverse transition metal complexes giving them promising electronic properties.[B174–181] This compound is beside the 1,4-diethynylferrocenylbutadiene a further main reagent in the present Ph.D. thesis for the synthesis of ferrocenylated cobalt carbonyl and iron carbonyl derivatives. The results there of are discussed in Chapter E.
FcC≡CPPh2 is accessible by a similar synthetic procedure as discussed for the synthesis of phosphinoacetylenes,[B182] which involves the reaction of Fc–C≡CH with nBuLi at –78 °C,
followed by treatment of thus formed FcC≡CLi with chlorodiphenylphospane Ph2PCl (Figure B27).[B178–180]
Figure B27: Synthesis of (ferrocenylethynyl)diphenylphosphane.[B178–180]
[B179,181] (FcC≡C)nPh3-nP=E (n = 1 – 3, E = O, Se), shows an interesting coordination behavior towards transition metals. Series of (ferrocenylethynyl)diphenylphospino complexes with Ru, Pd, Pt and Au as well as related complexes with other then phenyl substituents were synthesized and characterized.[B175–181]
In this respect bimetallic ruthenium(II) compounds 101 – 105 (Figure B28) were
6 synthesized by the reaction of (ferrocenylethynyl)phosphane with (RuCl2(η -p-
[B175] cymene))2, whereas the tetrametallic compound 106 (Figure B28) was formed by
6 [B175] treatment of (FcC≡C)(C≡CPPh)2P with an excess of (RuCl2(η -p-cymene))2. The obtained compounds 101 – 106 could be used as catalysts for the synthesis of β- oxopropyl benzoate from propargyl alcohol and benzoic acid.[B175]
50
101 – 105 106
c Figure B28: Ruthenium compounds 101 – 106 ((101) R = C6H5; (102) R = 2-CH3C6H4; (103) R = C4H3O; t c [B175] (104) R = Bu; (105) R = C6H11).
Another ruthenium dichloro complex, containing the (ferrocenylethynyl)diphenyl- phosphane ligand is (trans-RuCl2(PPh2C≡CFc)4) (107) which was obtained by the reaction of the phosphinoalkyne with RuCl2(PPh3)3. Complex 107 could be converted with
15 equiv. of HC≡CR into mer,cis-RuCl2(C=CHR)(PPh2(C≡CFc))3 (R = Ph, Tol) (108, 109).[B176]
Compound 107 could also be transformed into cis/trans-Ru(C≡CR)2(PPh2(C≡CFc))4 (R
= Ph, Tol) (110 – 113), by treatment with alkynes and NEt3 (Figure B29). Presence of
NaPF6 led to the formation of the trans- isomer, whereas in its absence the cis-isomer was formed.[B176]
107 108 (Ph), 109 (Tol)
51
110: R = Ph, 111: R = Tol 112: R = Ph, 113: R = Tol
Figure B29: Ruthenium complexes 107 – 113.[B176]
The ferrocenyl-substituted phosphinoalkynes (FcC≡C)nPPh3-n (n = 1 – 3) also can be applied in the synthesis of a series of structurally similar square-planar complexes with palladium and platinum. The palladium complexes 114 – 116 (Figure B30)[B178,179] were
obtained by the reaction of (FcC≡C)nPPh3-n with (cod)PdCl2 (cod = cyclo-1,5-
[B178] [B179] octadiene) or (Et2S)2PdCl2 in dichloromethane at ambient temperature. The cis- isomers of the palladium(II) complex 114[B178] and 116[B179] has been characterized in the solid state. At the same conditions cis- isomer of the platinum complex 117 was formed in
[B178] the reaction with K2PtCl4 (Figure B30). The cis- complex 114 could also be
quantitatively converted into trans-((FcC≡C)PPh2)2PdI2 (118) by treatment with KI in acetone (Figure B31).[B178]
114 – 116: (n = 1 – 3) 117
Figure B30: Palladium complexes 114 – 116 and platinum complex 117.[B178,179]
52 Ph2 Ph 2 KI, aceton 2 Fc P Cl Fc P I Pd Pd -2 KCl Fc P Cl I P Fc Ph2 Ph2 114 118
Figure B31: Conversion of the cis-palladium complexes 114 in trans- 118.[B178]
[B178] Additionally to the ((FcC≡C)PPh2)2PdCl2 complex 114, a series of palladium complexes with diverse substituents at the phosphorus atom such as C6H5 (119), 2-
c t c MeC6H4 (120), 2,4,6-Me3C6H2 (121), C4H3O (122), Bu (123), C6H11 (124) were obtained in our research group by the reaction of (FcC≡C)PR2 with either (cod)PdCl2 or
[B180] t PdCl2(SEt2)2 as the starting material (Figure B32). Interestingly, in case of R = Bu or
C C6H11, the use of PdCl2(SEt2)2 led to the formation of ((FcC≡C)PR2)2PdCl2 but in the reaction with (cod)PdCl2 the bridged bimetallic palladium complexes 125 and 126 were formed (Figure B32).[B180]
125, 126
119 – 124
c Figure B32: Synthesis of 119 – 126 (R = C6H5 (119), 2-MeC6H4 (120), 2,4,6-Me3C6H2 (121), C4H3O (122), t c t c [B180] Bu (123), C6H11 (124), Bu (125) and C6H11 (126)).
Beside 117, also the related bis- and tris-(ferrocenylethynyl)-substituted phosphane complexes 127, 128 were prepared.[B181]
117, n = 1; 127, n = 2; 128, n = 3
53
The cis-dichloroplatinum(II) species 117 could also be converted into trans-
Pt(C≡CFc)2(PPh2(C≡CFc))2 (129) by treatment with ferrocenylacetylene in presence of [CuI] and diisopropylamine.[B181]
Similar conversions into mixed ferrocenylethynyl– and (ferrocenylethynyl)diphenyl- phosphane complexes with platinum (130 – 135) were performed in dichloromethane by
t the displacement of cod (cod = cyclo-1,5-octadiene) in Pt(C≡CR)2(cod), (R = Fc, Ph, Bu) with two equiv of the corresponding alkynylphosphane (Figure B33).[B177] The cis-Pt
complex 130 was converted into the trans isomer 129 by refluxing in NEt3 utilizing CuI as a catalyst (Figure B33).[B177] Other mixed platinum complexes 136 – 139 were obtained
by displacement of tetrahydrothiophene (tht) in cis or trans-Pt(Rf)2(tht)2 (Rf = C6F5) by
[B177] using one or two equiv of PPh2(C≡CFc) (Figure B33).
Pt(C CR)2cod v i
Fc Ph2 R R Ph2 Fc P P Pt Pt 136 137 P P Fc Ph2 R R Ph2 Fc
130 – 132 (R = Fc, Ph, tBu) 133 – 135
Fc Ph2 Fc Fc Ph2 Fc P iv P Pt Pt P P Fc Fc Ph2 Fc Fc Ph2 130 129 138 139
Figure B33: Synthesis of mixed alkynylphosphine and ethynylferrocene complexes with platinum. (i): 2 equiv. PPh2C≡CFc, CH2Cl2. (ii): 1 equiv PPh2C≡CFc, CH2Cl2. (iii): 1 equiv PPh2C≡CPh, CH2Cl2. (iv): reflux NEt3, t [B177] CuI as catalyst. (v): 2 equiv PPh2C≡CR (R = Fc, Ph, Bu).
The reaction of 130 – 132 and 136 with cis-Pt(Rf)2(thf)2 (thf = tetrahydrofuran) led to formation of complexes 140 – 143.[B177]
140 – 142 143
54
Related gold(I) chlorid complexes 144 and 145 were obtained from the respective (ferrocenylethynyl)phosphanes by the reaction with [AuCl(tht)].[B181]
144 145
Using the same methodology as in the synthesis of the platinum complex 130, the gold(I) chlorid compounds 144, 145 gave by the reaction with ethynylferrocene or ethynyl- ruthenocene the gold complexes 146 – 149.[B181,182]
5 5 5 5 146: R = Fe(η -C5H4)(η -C5H5) 148: R = Fe(η -C5H4)(η -C5H5) 5 5 5 5 147: R = Ru(η -C5H4)(η -C5H5) 149: R = Ru(η -C5H4)(η -C5H5)
The above described gold complexes 145 – 147 possess anticancer properties.[B183]
55 References
[B1] C. Creutz, H. Taube, J. Am. Chem. Soc. 1969, 91, 3988–3989.
[B2] I. M. Klotz, G. H. Czerlinski, H. A. Fiess, J. Am. Chem. Soc. 1958, 80, 2920–2923.
[B3] Y. Kim, C. M. Lieber, Inorg. Chem. 1989, 28, 3990–3992.
[B4] D. E. Richardson, H. Taube, J. Am. Chem. Soc. 1983, 105, 40–51.
[B5] A.-C. Ribou, J.-P. Launay, K. Takahashi, T. Nihira, S. Tarutani, C. W. Spangler, Inorg. Chem. 1994, 33, 1325–1329.
[B6] J. R. Reimers, N. S. Hush, Inorg. Chem. 1990, 29, 4510–4513.
[B7] M. A. Nemzek, R. W. Callahan, J. Chem. Soc., Chem. Commun. 1980, 1231–1232.
[B8] J. R. Gispert, in Coordination Chemistry, WILEY-VCH, Weinheim, 2008, pp. 403–432.
[B9] P. Day, N. S. Hush, R. J. H. Clark, Phil. Trans. R. Soc. A 2008, 366, 5–14.
[B10] M. B. Robin, P. Day, Adv. Inorg. Chem. Radiochem. 1967, 10, 247–422.
[B11] G. C. Allen, N. S. Hush, Prog. Inorg. Chem. 1967, 8, 357–390.
[B12] N. S. Hush, Prog. Inorg. Chem. 1967, 8, 391–444.
[B13] N. S. Hush, Electrochim. Acta 1968, 13, 1005–1023.
[B14] D. M. D’Alessandro, F. R. Keene, Chem. Soc. Rev. 2006, 35, 424–440.
[B15] J. R. Gispert, in Coordination Chemistry, WILEY-VCH, Weinheim, 2008, pp. 377–401.
[B16] R. F. Winter, Organometallics 2014, 33, 4517–4536.
[B17] A. Hildebrandt, H. Lang, Organometallics 2013, 32, 5640–5653.
[B18] A. Hildebrandt, H. Lang, Dalton Trans. 2011, 40, 11831–11837.
[B19] A. Hildebrandt, D. Schaarschmidt, R. Claus, H. Lang, Inorg. Chem. 2011, 50, 10623– 10632.
[B20] P. Aguirre-Etcheverry, D. O’Hare, Chem. Rev. 2010, 110, 4839–4864.
[B21] P. Mücke, M. Linseis, S. Záliš, R. F. Winter, Inorg. Chim. Acta 2011, 374, 36–50.
[B22] J. Zhang, P. R. Unwin, J. Chem. Soc., Perkin Trans. 2 2001, 1608–1612.
[B23] B. S. Brunschwig, C. Creutz, N. Sutin, Chem. Soc. Rev. 2002, 31, 168–184.
[B24] S. B. Piepho, E. R. Krausz, P. N. Schatz, J. Am. Chem. Soc. 1978, 100, 2996–3005.
[B25] S. B. Piepho, J. Am. Chem. Soc. 1990, 112, 4197–4206.
[B26] P. Zanello, F. F. de Biani, C. Nervi, Inorganic Electrochemistry: Theory, Practice and Application, RSC Publishing, Cambridge, UK, 2012.
56 [B27] P. E. Whitson, H. W. VandenBorn, D. H. Evans, Anal. Chem. 1973, 45, 1298–1306.
[B28] J. Heinze, Angew. Chem. Int. Ed. 1984, 23, 831–847.
[B29] A. J. Bard, Y. Faulkner, Electrochemical Methods: Fundamentals and Applications, WILEY-VCH, 2000.
[B30] C. Yarnitzky, Y. Friedman, Anal. Chem. 1975, 47, 876–880.
[B31] A. Ceccon, S. Santi, L. Orian, A. Bisello, Coord. Chem. Rev. 2004, 248, 683–724.
[B32] S. V. Lindeman, S. V. Rosokha, D. Sun, J. K. Kochi, J. Am. Chem. Soc. 2002, 124, 843– 855.
[B33] J. M. Speck, M. Korb, T. Rüffer, A. Hildebrandt, H. Lang, Organometallics 2014, 33, 4813–4823.
[B34] A. Donoli, A. Bisello, R. Cardena, A. Ceccon, M. Bassetti, A. D’Annibale, C. Pasquini, A. Raneri, S. Santi, Inorganica Chim. Acta 2011, 374, 442–446.
[B35] A. Donoli, A. Bisello, R. Cardena, C. Prinzivalli, S. Santi, S. Chimiche, Organometallics 2013, 32, 1029–1036.
[B36] S. Záliš, R. F. Winter, W. Kaim, Coord. Chem. Rev. 2010, 254, 1383–1396.
[B37] J. Maurer, B. Sarkar, B. Schwederski, W. Kaim, R. F. Winter, S. Záliš, Organometallics 2006, 25, 3701–3712.
[B38] A.-C. Ribou, J.-P. Launay, M. L. Sachtleben, H. Li, C. W. Spangler, Inorg. Chem. 1996, 35, 3735–3740.
[B39] H. H. Shah, R. A. Al-Balushi, M. K. Al-Suti, M. S. Khan, C. H. Woodall, K. C. Molloy, P. R. Raithby, T. P. Robinson, S. E. C. Dale, F. Marken, Inorg. Chem. 2013, 52, 4898–4908.
[B40] A. Hildebrandt, T. Rüffer, E. Erasmus, J. C. Swarts, H. Lang, Organometallics 2010, 29, 4900–4905.
[B41] P. Mücke, R. F. Winter, K. Kowalski, J. Organomet. Chem. 2013, 735, 10–14.
[B42] P. Mücke, R. F. Winter, I. Novak, K. Kowalski, J. Organomet. Chem. 2012, 717, 14–22.
[B43] U. Pfaff, G. Filipczyk, A. Hildebrandt, M. Korb, H. Lang, Dalton Trans. 2014, 43, 16310–16321.
[B44] F. Barrière, W. E. Geiger, J. Am. Chem. Soc. 2006, 3980–3989.
[B45] R. J. LeSuer, C. Buttolph, W. E. Geiger, Anal. Chem. 2004, 76, 6395–6401.
[B46] K. A. Goldsby, T. J. Meyer, Inorg. Chem. 1984, 23, 3002–3010.
[B47] F. Barrière, N. Camire, W. E. Geiger, U. T. Mueller-Westerhoff, R. Sanders, J. Am. Chem. Soc. 2002, 124, 7262–7263.
[B48] H. J. Gericke, N. I. Barnard, E. Erasmus, J. C. Swarts, M. J. Cook, M. A. S. Aquino, Inorg. Chim. Acta 2010, 363, 2222–2232. [B49] F. Barrière, Organometallics 2014, 33, 5046–5048.
57 [B50] F. Paul, C. Lapinte, Coord. Chem. Rev. 1998, 178–180, 431–509.
[B51] B. Kim, J. M. Beebe, C. Olivier, S. Rigaut, D. Touchard, J. G. Kushmerick, X.-Y. Zhu, D. Frisbie, J. Phys. Chem. C 2007, 111, 7521–7526.
[B52] K. Kowalski, M. Linseis, R. F. Winter, M. Zabel, S. Záliš, H. Kelm, H. J. Krüger, B. Sarkar, W. Kaim, Organometallics 2009, 28, 4196–4209.
[B53] D. O. Cowan, F. Kaufman, J. Am. Chem. Soc. 1970, 92, 219–220.
[B54] C. LeVanda, K. Bechgaard, D. O. Cowan, U. T. Mueller-Westerhoff, P. Eilbracht, G. A. Candela, R. L. Collins, J. Am. Chem. Soc. 1976, 98, 3181–3187.
[B55] C. Levanda, K. Bechgaard, D. O. Cowan, J. Org. Chem. 1976, 41, 2700–2704.
[B56] J. A. Christie, R. P. Forrest, S. A. Corcelli, N. A. Wasio, R. C. Quardokus, R. Brown, S. A. Kandel, Y. Lu, C. S. Lent, K. W. Henderson, Angew. Chem. Int. Ed. 2015, 10, 15448– 15451.
[B57] J. Ma, N. Krauße, H. Butenschön, Eur. J. Org.Chem. 2015, 2015, 4510–4518.
[B58] R.-J. Xie, L.-M. Han, N. Zhu, Y.-Y. Gao, H.-L. Hong, Q.-L. Suo, J. Coord. Chem. 2015, 68, 449–460.
[B59] R.-J. Xie, L. M. Han, N. Zhu, H. L. Hong, Q. L. Suo, P. Fu, Polyhedron 2012, 38, 7–14.
[B60] K. Kaleta, A. Hildebrandt, F. Strehler, P. Arndt, H. Jiao, A. Spannenberg, H. Lang, U. Rosenthal, Angew. Chem. Int. Ed. 2011, 50, 11248–11252.
[B61] K. Kaleta, F. Strehler, A. Hildebrandt, T. Beweries, P. Arndt, T. Rüffer, A. Spannenberg, H. Lang, U. Rosenthal, Chem. Eur. J. 2012, 18, 12672–12680.
[B62] A. S. Romanov, T. V. Timofeeva, M. Y. Antipin, J. Organomet. Chem. 2011, 696, 3822– 3825.
[B63] M. Zora, A. T. Tumay, O. Büyükgüngör, Tetrahedron 2007, 63, 4018–4026.
[B64] M. Zora, C. Acikgöz, M. Odabasoglu, O. Büyükgüngör, J. Organomet. Chem. 2007, 692, 1571–1578.
[B65] E. I. Klimova, T. K. Berestneva, R. a. Toscano, J. M. Méndez Stivalet, M. M. Garcia, Synth. Commun. 2007, 37, 889–900.
[B66] J. Jiao, G. J. Long, L. Rebbouh, F. Grandjean, A. M. Beatty, T. P. Fehlner, J. Am. Chem. Soc. 2005, 127, 17819–17831.
[B67] T. Mochida, S. Yamazaki, J. Chem. Soc., Dalton Trans. 2002, 3559–3564.
[B68] L.-A. Hore, C. J. McAdam, J. L. Kerr, N. W. Duffy, B. H. Robinson, J. Simpson, Organometallics 2000, 19, 5039–5048.
[B69] M. D. Rausch, F. A. Higbie, G. F. Westover, A. Clearfield, R. Gopal, J. M. Troup, I. Bernal, J. Organomet. Chem. 1978, 149, 246–264.
[B70] P. Mathur, A. K. Singh, V. K. Singh, P. Singh, R. Rahul, S. M. Mobin, C. Thöne, Organometallics 2005, 24, 4793–4798.
58 [B71] M. Rosenblum, N. Brawn, J. Papenmeier, M. Applebaum, J. Organomet. Chem. 1966, 6, 173–180.
[B72] Z. Yuan, G. Stringer, I. R. Jobe, D. Kreller, K. Scott, L. Koch, N. J. Taylor, T. B. Marder, J. Organomet. Chem. 1993, 452, 115–120.
[B73] J.-G. Rodriguez, A. Oñate, R. M. Martin-Villamil, I. Fonseca, J. Organomet. Chem. 1996, 513, 71–76.
[B74] F. W. Li, Q. L. Suo, H. L. Hong, N. Zhu, Y. Q. Wang, L. L. Guo, L. M. Han, J. Supercrit. Fluids 2014, 92, 70–74.
[B75] D. Wang, J. Li, N. Li, T. Gao, S. Hou, B. Chen, Green Chem. 2010, 12, 45–48.
[B76] A. A. Koridze, V. L. Zdanovich, N. V Andrievskaya, Y. Siromakhova, P. V Petrovskii, M. G. Ezernitskaya, Russ. Chem. Bull. 1996, 45, 1200–1206.
[B77] P. Mathur, A. Das, S. Chatterjee, S. M. Mobin, J. Organomet. Chem. 2008, 693, 1919– 1926.
[B78] R. D. Adams, B. Qu, M. D. Smith, T. A. Albright, Organometallics 2002, 21, 2970– 2978.
[B79] R. D. Adams, Organometallics 2000, 19, 2411–2413.
[B80] E. Champeil, S. M. Draper, J. Chem. Soc., Dalton Trans., 2001, 6, 1440–1447.
[B81] Q.-L. Suo, L.-M. Han, Y.-B. Wang, J.-H. Ye, N. Zhu, X.-B. Leng, J. Sun, J. Coord. Chem. 2004, 57, 1591–1601.
[B82] M. I. Bruce, B. W. Skelton, A. H. White, N. N. Zaitseva, J. Organomet. Chem. 2002, 650, 188–197.
[B83] P. Mathur, V. D. Avasare, S. M. Mobin, J. Clust. Sci. 2009, 20, 399–415.
[B84] G. Xu, B. Xi, J. B. Updegraff, J. D. Protasiewicz, T. Ren, Organometallics 2006, 25, 5213–5215.
[B85] R. D. Adams, O.-S. Kwon, B. Qu, M. D. Smith, Organometallics 2001, 20, 5225–5232.
[B86] R. D. Adams, B. Qu, M. D. Smith, Organometallics 2002, 21, 3867–3872.
[B87] P. Mathur, R. Shyam Ji, S. Boodida, A. K. Singh, S. M. Mobin, J. Organomet. Chem. 2010, 695, 1986–1992.
[B88] J. Kotz, G. Neyhart, W. J. Vining, M. D. Rausch, Organometallics 1983, 2, 79–82.
[B89] M. J. Powers, T. J. Meyer, J. Am. Chem. Soc. 1978, 100, 4393–4398.
[B90] J. A. Kramer, D. N. Hendrickson, Inorg. Chem. 1980, 19, 3330–3337.
[B91] D. O. Cowan, C. LeVanda, J. Park, F. Kaufman, Acc. Chem. Res. 1973, 6, 1–7.
[B92] W. H. Morrison, D. N. Hendrickson, Inorg. Chem. 1975, 14, 2331–2346.
[B93] E. Negishi, F. Liu, Metal-Catalyzed Cross-Coupling Reactions, Wiley-VCH, New York, 1997.
59 [B94] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 1975, 16, 4467–4470.
[B95] K. Sonogashira, J. Organomet. Chem. 2002, 653, 46–49.
[B96] Y. Yu, A. D. Bond, P. W. Leonard, U. J. Lorenz, T. V. Timofeeva, K. P. C. Vollhardt, G. D. Whitener, A. A. Yakovenko, Chem. Commun. 2006, 2572.
[B97] A. K. Diallo, J. C. Daran, F. Varret, J. Ruiz, D. Astruc, Angew. Chem. Int. Ed. 2009, 48, 3141–3145.
[B98] A. K. Diallo, C. Absalon, J. Ruiz, D. Astruc, J. Am. Chem. Soc. 2011, 133, 629–641.
[B99] Y. Yu, A. D. Bond, P. W. Leonard, K. P. C. Vollhardt, G. D. Whitener, Angew. Chem. Int. Ed. 2006, 45, 1794–1799.
[B100] A. Hildebrandt, D. Schaarschmidt, L. Van As, J. C. Swarts, H. Lang, Inorg. Chim. Acta 2011, 374, 112–118.
[B101] A. Hildebrandt, U. Pfaff, H. Lang, Rev. Inorg. Chem. 2011, 31, 111–141.
[B102] U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Hahn, S. Liebing, J. Kortus, H. Lang, Organometallics 2012, 31, 6761–6771.
[B103] J. M. Speck, R. Claus, A. Hildebrandt, T. Rüffer, E. Erasmus, L. van As, J. C. Swarts, H. Lang, Organometallics 2012, 31, 6373–6380.
[B104] A. Hildebrandt, D. Schaarschmidt, H. Lang, Organometallics 2011, 30, 556–563.
[B105] J. M. Speck, D. Schaarschmidt, H. Lang, Organometallics 2012, 31, 1975–1982.
[B106] P. R. Chopade, J. Louie, Adv. Synth. Catal. 2006, 348, 2307–2327.
[B107] M. J. Calhorda, P. J. Costa, K. A. Kirchner, Inorg. Chim. Acta 2011, 374, 24–35.
[B108] J. A. Varela, C. Saá, Synlett 2008, 17, 2571–2578.
[B109] A. Nakamura, N. Hagihara, Bull. Chem. Soc. Jpn. 1961, 34, 452–453.
[B110] M. D. Rausch, R. A. Genetti, J. Am. Chem. Soc. 1967, 89, 5502–5503.
[B111] M. D. Rausch, R. A. Genetti, J. Org. Chem. 1970, 35, 3888–3897.
[B112] M. D. Rausch, Pure Appl. Chem. 1972, 30, 523–538.
[B113] M. D. Rausch, I. Bernal, B. R. Davies, A. Siegel, F. A. Higbie, G. F. Westover, J. Coord. Chem. 1973, 3, 149–159.
[B114] A. Clearfield, R. Gopal, M. D. Rausch, E. F. Tokas, F. A. Higbie, I. Bernal, J. Organomet. Chem. 1977, 135, 229–248.
[B115] S. Fiorentini, B. Floris, P. Galloni, F. Grepioni, M. Polito, P. Tagliatesta, Eur. J. Org. Chem. 2006, 1726–1732. [B116] Y.-Q. Wang, L. M. Han, Q. L. Suo, N. Zhu, J. M. Hao, R. J. Xie, Polyhedron 2013, 54, 221–227.
[B117] Y.-Q. Wang, L.-M. Han, Q.-L. Suo, N. Zhu, F.-W. Li, Polyhedron 2014, 71, 42–46.
60 [B118] N. Singh, A. J. Elias, J. Chem. Sci. 2011, 123, 853–860.
[B119] N. Singh, A. J. Elias, Dalton Trans. 2011, 40, 4882–4891.
[B120] H. V Nguyen, M. R. Yeamine, J. Amin, M. Motevalli, C. J. Richards, J. Organomet. Chem. 2008, 693, 3668–3676.
[B121] C. Schaefer, D. B. Werz, T. H. Staeb, R. Gleiter, F. Rominger, Organometallics 2005, 24, 2106–2113.
[B122] J. A. Varela, C. Saá, Chem. Rev. 2003, 103, 3787–3801.
[B123] Y. Wakatsuki, O. Nomura, K. Kitaura, M. Keiji, H. Yamazaki, J. Organomet. Chem. 1983, 105, 1907–1912.
[B124] T. D. Coyle, R. B. King, E. Pitcher, S. L. Stafford, P. Treichel, F. G. A. Stone, J. lnorg. Nucl. Chem. 1961, 20, 172–173.
[B125] A. Stockis, R. Hoffmann, J. Am. Chem. Soc. 1980, 102, 2952–2962.
[B126] N. Agenet, V. Gandon, K. P. C. Vollhardt, M. Malacria, C. Aubert, J. Am. Chem. Soc. 2007, 129, 8860–8871.
[B127] S. Murai, F. Kakiuchi, S. Sekine, Y. Tanaka, A. Kamatani, M. Sonoda, N. Chatani, Nature 1993, 366, 529–531.
[B128] S. I. Kozhushkov, H. K. Potukuchi, L. Ackermann, Catal. Sci. Technol. 2013, 3, 562– 571.
[B129] J. Wencel-Delord, T. Dröge, F. Liu, F. Glorius, Chem. Soc. Rev. 2011, 40, 4740–4761.
[B130] D. A. Colby, R. G. Bergman, J. A. Ellman, Chem. Rev. 2010, 110, 624–655.
[B131] T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147–1169.
[B132] S. Murahashi, J. Am. Chem. Soc. 1955, 77, 6403–6404.
[B133] D. Tilly, G. Dayaker, P. Bachu, Catal. Sci. Technol. 2014, 4, 2756.
[B134] J. R. Hummel, J. A. Ellman, J. Am. Chem. Soc. 2015, 137, 490–498.
[B135] K. Gao, N. Yoshikai, Acc. Chem. Res. 2014, 47, 1208–1219.
[B136] L. Grigorjeva, O. Daugulis, Org. Lett. 2014, 16, 4684–4687.
[B137] M. Albrecht, Chem. Rev. 2010, 110, 576–623.
[B138] P.-S. Lee, T. Fujita, N. Yoshikai, J. Am. Chem. Soc. 2011, 133, 17283–17295.
[B139] T. Yamakawa, N. Yoshikai, Org. Lett. 2013, 15, 196–199.
[B140] K. Gao, P.-S. Lee, T. Fujita, N. Yoshikai, J. Am. Chem. Soc. 2010, 132, 12249–12251.
[B141] H. F. Klein, R. Beck, U. Flörke, H. J. Haupt, Eur. J. Inorg. Chem. 2002, 3305–3312.
[B142] H. Klein, R. Beck, U. Flörke, H.-J. Haupt, Eur. J. Inorg. Chem. 2003, 1380–1387.
[B143] H. F. Klein, S. Camadanli, R. Beck, D. Leukel, U. Flörke, Angew. Chem. Int. Ed. 2005, 44, 975–977.
61 [B144] C. P. Lenges, M. Brooldaart, B. E. Grant, J. Organomet. Chem. 1997, 528, 199–203.
[B145] H. A. Patel, R. G. Fischer, A. J. Carty, D. V Naik, G. J. Palenik, J. Organomet. Chem. 1973, 60, 49–52.
[B146] W. F. Smith, J. Yule, N. J. Taylor, H. N. Paik, A. J. Carty, Inorg. Chem. 1977, 16, 1593– 1600.
[B147] A. J. Carty, Pure Appl. Chem. 1982, 54, 113–130.
[B148] A. A. Cherkas, L. H. Randall, S. A. Maclaughlin, G. N. Mott, N. J. Taylor, A. J. Carty, Organometallics 1988, 7, 969–977.
[B149] D. Nucciarone, S. A. MacLaughlin, N. J. Taylor, A. J. Carty, Organometallics 1988, 7, 106–117.
[B150] E. Sappa, A. Tiripicchio, P. Braunstein, Chem. Rev. 1983, 83, 203–239.
[B151] E. Sappa, A. Tiripicchio, P. Braunstein, Coord. Chem. Rev. 1985, 65, 219–284.
[B152] G. Gervasio, E. Sappa, A. Secco, J. Organomet. Chem. 2014, 751, 111–152.
[B153] M. J. Mays, K. Sarveswaran, G. A. Solan, Inorg. Chim. Acta 2003, 354, 21–28.
[B154] H. N. Paik, A. J. Carty, K. Dymock, G. J. Palenik, J. Organomet. Chem. 1974, 70, 17–20.
[B155] A. J. Carty, H. N. Paik, G. J. Palenik, Inorg. Chem. 1977, 16, 300–305.
[B156] P. Mathur, D. K. Rai, R. S. Ji, B. Pathak, S. Boodida, S. M. Mobin, RSC Adv. 2013, 3, 26025–26034.
[B157] H. A. Patel, A. J. Carty, N. K. Hota, J. Organomet. Chem. 1973, 50, 247–263.
[B158] T. M. Wido, M. Calligarist, G. Nardin, Organometallics 1988, 2, 452–458.
[B159] H. Lang, M. Leise, L. Zsolnai, J. Organomet. Chem. 1991, 410, 379–388.
[B160] E. Louattani, J. Suades, A. Alvarez-larena, J. F. Piniella, G. Germain, J. Organomet. Chem. 1996, 506, 121–127.
[B161] C. J. Adams, M. I. Bruce, E. Horn, E. R. T. Tiekink, J. Chem. Soc. Dalton Trans. 1992, 1157–1164.
[B162] H. Lang, L. Zsolnai, J. Organomet. Chem. 1989, 369, 131–135.
[B163] M. I. Bruce, F. de Montigny, M. Jevric, C. Lapinte, B. Skelton, M. Smith, A. White, J. Organomet. Chem. 2004, 689, 2860–2871.
[B164] C. S. Guo, C. M. Weng, F. E. Hong, Eur. J. Inorg. Chem. 2010, 3220–3228.
[B165] F. E. Hong, Y. C. Lai, Y. J. Ho, Y. C. Chang, J. Organomet. Chem. 2003, 688, 161–167.
[B166] J. C. Jeffery, R. M. S. Pereira, M. D. Vargasb, M. J. Wentc, J. Chem. Soc. Dalt. Trans 1995, 1805–1811.
[B167] H. Lang, U. Lay, J. Organomet. Chem. 1990, 388, C1–C4.
[B168] U. Lay, H. Lang, J. Organomet. Chem. 1991, 418, 79–89.
62 [B169] H. Lang, U. Lay, J. Organomet. Chem. 1992, 441, 389–396.
[B170] C. Georgi, A. Hildebrandt, A. Tuchscherer, S. Oswald, H. Lang, Z. Anorg. Allg. Chem. 2013, 639, 2532–2535.
[B171] C. Georgi, A. Hildebrandt, T. Waechtler, S. E. Schulz, T. Gessner, H. Lang, J. Mater. Chem. C 2014, 2, 4676–4682.
[B172] C. Georgi, M. Hapke, I. Thiel, A. Hildebrandt, T. Waechtler, S. E. Schulz, H. Lang, Thin Solid Films 2015, 578, 180–184.
[B173] E. C. Constable, C. E. Housecroft, M. Neuburger, M. Zehnder, Organometallics 1999, 18, 2565–2567.
[B174] K. Heinze, H. Lang, Organometallics 2013, 32, 5623–5625.
[B175] B. Milde, T. Rüffer, H. Lang, Inorg. Chim. Acta 2012, 387, 338–345.
[B176] J. Berenguer, M. Bernechea, J. Fernández, B. Gil, E. Lalinde, M. T. Moreno, S. Ruiz, S. Sánchez, Organometallics 2011, 30, 4665–4677.
[B177] Á. Díez, E. Lalinde, M. T. Moreno, S. Sánchez, Dalton Trans. 2009, 3434–3446.
[B178] T. Baumgartner, M. Fiege, F. Pontzen, R. Arteaga-Müller, Organometallics 2006, 25, 5657–5664.
[B179] A. Jakob, B. Milde, P. Ecorchard, C. Schreiner, H. Lang, J. Organomet. Chem. 2008, 693, 3821–3830.
[B180] B. Milde, D. Schaarschmidt, P. Ecorchard, H. Lang, J. Organomet. Chem. 2012, 706– 707, 52–65.
[B181] A. Jakob, P. Ecorchard, M. Linseis, R. F. Winter, H. Lang, J. Organomet. Chem. 2009, 694, 655–666.
[B182] A. J. Carty, N. K. Hota, T. W. Ng, H. A. Patel, T. J. O’Connor, Can. J. Chem. 1971, 49, 2706–2711.
[B183] E. Fourie, E. Erasmus, J. C. Swarts, A. Jakob, H. Lang, G. K. Joone, C. E. J. Van Rensburg, Anticancer Res. 2011, 31, 825–830.
63 CHAPTER C Multiferrocenyl Cobalt-Based Sandwich Compounds
G. Filipczyk, S. W. Lehrich, A. Hildebrandt, T. Rüffer, D. Schaarschmidt, M. Korb, H. Lang, Eur. J. Inorg. Chem., 2017, 263–275.
All the described products were synthesized, isolated and characterized by the author. The crystal X-ray structure data were collected, processed and described by Tobias Rüffer, Dieter Schaarschmidt and Marcus Korb. The (spectro)electrochemical experiments were conducted by the author. The discussion of the results was accomplished in cooperation with Steve Lehrich and Alexander Hildebrandt.
1 Introduction
Recently, multiferrocenyl cyclic and heterocyclic compounds with aromatic or antiaromatic core moieties have been at the focus of chemical research, because of, for example, their uncommon molecular structures and their extraordinary electrochemical and spectroelectrochemical properties.[C1–7] The investigations of such compounds gave an insight into the electronic structures and provided an understanding of the chemical behavior and electron-transfer processes between interacting sites in the appropriate mixed-valent complexes. The choice of ferrocenyl groups, as a common part, is a result of the electrochemical reversibility and high stability of the FeII/FeIII redox couple.[C8–13]
These kinds of compounds can be considered as model systems with potential applications, including their use as electroactive materials and components of electronic
[C7,14–20] 4 5 circuits. Examples of multiferrocenyl compounds are Rausch's [Co(η C4Fc4)(η -
[C21,22] c 5 C5H5)], perferrocenylated heterocycles of the type C4Fc4E [E = S, O, NMe, NPh, Zr(η -
[C1,2,23–27] [C28] C5H5)2], and 3,3′,4,4′,5,5′-hexaferrocenyl-2,2′bithiophene from our research group, and Vollhardt's as well as Astruc's (penta- and hexaferrocenyl)benzene and hexa(ferrocenylethynyl)benzene compounds.[C3,29,30] In addition, half-sandwich
5 [C31] 4 [C32] compounds including Mn(η -C5Fc5)(CO)3 or Fe(η C4Fc4)(CO)3 represent multi-
5 5 ferrocenyl-substituted organometallic species (Fc = Fe(η -C5H4)(η -C5H5)).
1,4-Diferrocenylbutadiyne offers the possibility to build complex polymetallic structures containing several ferrocenyl groups at a discrete molecule by applying the
64 known cyclization protocol.[C33–39] In this article, we present a “one-pot” synthetic methodology affording a range of multiferrocenylcrowded cyclodimerized and cyclotrimerized species obtained from the reaction of FcC≡C–C≡CFc with Co(η5-
C5H5)(CO)2. Thestructural, chemical, and physical properties of these compounds including their electrochemical and spectroelectrochemical behavior is discussed.
2 Results and Discussion
2.1 Synthesis and Characterization
The reaction of 1,4-diferrocenylbutadiyne (1) with dicarbonyl(η5-cyclopentadienyl)- cobalt(I) (2) afforded a series of cyclic multiferrocenyl compounds as shown in Figure C1. The applied reaction conditions, such as temperature, molar ratio of the reactants and application of a steady argon or carbon monoxide flow through the reaction vessel, allowed the controlled modification of the product composition. Organometallic compounds 3–7 are solids stable towards air and moisture and can be dissolved in most common polar and nonpolar organic solvents.
Compounds 3–7 are accessible by a “one-pot” synthesis procedure including the following three reactions: (i) cyclodimerization of 1 affording cobalt cyclobutadiene cyclopentadienyl species 3a,b and 4a,b, (ii) cyclotrimerization and C–H bond activation yielding 5a,b[C34] (in Chapter D as compounds 3a,b) and 5c, and (iii) cyclodimerization with consecutive CO insertion producing cobalt cyclopentadienone cyclopentadienyl compounds 6a,b,c and 7 (Figure C1).
After appropriate workup, compounds 3–7 could be isolated by column chromatography and crystallization in low to moderate yields (see the Experimental Section). Organometallics 3–7 were characterized by NMR spectroscopic analysis (1H, 13C{1H}), UV/Vis, and IR spectroscopy, high-resolution ESI-TOF mass spectrometry, and elemental analysis. In addition, the molecular structures of 3a,b, 4a, 6a and 7 in the solid state were determined by single-crystal X-ray diffraction studies. Given that the newly synthesized compounds feature redox-active ferrocenyl functionalities, the electrochemical properties of these species were studied by means of cyclic voltammetry
65 (CV), square-wave voltammetry (SWV) and in situ UV/Vis/NIR spectroelectrochemistry to determine the degree of electronic coupling between the metal centers in the mixed- valent species.
The highest yield for 3a,b was achieved when 1 was treated with a twofold excess of 2 at a temperature of 140 °C (m-xylene) and a reaction time of 36 h. To avoid competitive formation of cobalt cyclopentadienones, bubbling of argon through the reaction solution was beneficial to remove the carbon monoxide released from 2. In contrast, application of a CO gas flow through the reaction solution increased the formation of cobalt cyclopentadienones 6a–c (see the Experimental Section). Reducing the reaction temperature to 100 °C or even to 60 °C resulted in a drop of the conversion of the reagents 1 and 2 into 3. The same was observed when the reaction times were shortened.
5 5 5 Figure C1. Reaction of FcC≡C–C≡CFc (Fc = Fe(η -C5H4)(η -C5H5)) (1) with Co(η -C5H5)(CO)2 (2) affording 3 – 7. For 5a,b see reference [C34] (in Chapter D compounds 3a,b).
Within the reaction of 1 with 2, the most favored isomer formed was 3a, whereas 3b was obtained in only minor amounts (Figure C1). To isolate 3b from 3a, column chromatography and crystallization were required, whereby 3a could be isolated as an orange solid. However, 3b could only be obtained in a mixture with 3a, and the appropriate purification methods (see above) only allowed enriching the respective
66 5 4 c mixtures by 3b. Compounds 3a,b structurally correspond to Co(η -C5H5)(η - C4R4) (R = Ph,[C35,40] Fc[C21,22]), which was first prepared by Rausch and co-workers.
Although 3b could not be isolated in pure form (see above), NMR studies enabled the identification of the 1,2-isomer in the presence of the 1,3-isomer by comparison of their NMR spectra (see the Supporting Information, Figures CS8 and CS12). The 1H NMR spectrum of 3a is characterized by four resonance signals for the C5H4 groups with a pseudo-triplet multiplicity for the Fc and the FcC≡C groups (the signals of the Hβ atoms of the Fc and the FcC≡C unit are unresolved and appear together as a multiplet) and three singlets for the C5H5 ligands in a 2:2:1 integral ratio (Fc/FcC≡C/Co). In contrast, the α,α′- and β,β′-protons of both chemically different C5H4 groups of the 1,2-isomer 3b are diastereotopic, and hence eight resonance signals were observed, whereas parts of the
C5H4 proton signals are in a spectral range close to each other and hence are not fully
13 resolved. The C{1H} NMR spectrum of 3a shows three resonance signals for the C5H5
5 units at δ = 69.7, 70.1, and 82.2 ppm for Fc, FcC≡C, and Co(η -C5H5), respectively, two sets of Cα (δ = 66.5 and 71.3 ppm) and Cβ (δ = 68.6 and 69.0 ppm) carbon signals as well as six quaternary carbon signals at δ = 52.4, 66.9, 77.7, 80.4, 83.2, and 90.9 ppm. The 13C{1H}
NMR spectrum of 3b is more complex and shows, besides the three C5H5 carbon resonances (δ = 69.7, 70.3, and 82.6 ppm), four separate carbon signals for the ferrocenyl
C5H4 units (δ = 67.7, 67.9, 68.3, and 68.4 ppm), two related C5H4 signals (FcC≡C) (δ = 69.0, 71.4 ppm), and six quaternary carbon signals (δ = 56.5, 66.8, 76.7, 80.6, 82.5, and 91.9 ppm) (see the Experimental Section and the Supporting Information). Crystallization from n-hexane/dichloromethane solutions (ratio 3:1, v/v) containing a mixture of both isomers, allowed the separation of a few single crystals of 3b from 3a, and hence both isomers could structurally be characterized by X-ray crystallography (Figure C2).
67 Figure C2. ORTEP diagram (30 % probability level) of the molecular structure of 3aA (left) and 3b (right). Hydrogen atoms and the disordered dichloromethane molecule as packing solvent (3aA) are omitted for clarity. 3aA: Selected bond lengths (Å) and angles (°): C1–C3 1.462(6), C1–C4 1.473(6), C2–C3 1.465(6), C2– C4 1.471(6), C10–C11 1.201(6), C22–C23 1.199(6), Co–D(C5H5) 1.6853(6), Co–D(C4) 1.7092(6), average Fe– D 1.650; C1–C10–C11 178.0(5), C2–C22–C23 177.1(5), C10–C11–C12 177.0(5), C22–C23–C24 176.4(5), D– Co–D 176.77(5), average D–Fe–D 178.7. 3b: selected bond lengths (Å) and angles (°): C1–C2 1.461(14), C1– C4 1.477(14), C2–C3 1.467(13), C3–C4 1.499(14), C30–C31 1.194(14), C42–C43 1.209(15), Co–D(C5H5) 1.6754(16), Co–D(C4) 1.7004(16), average Fe–D 1.658; C3–C30–C31 177.7(11), C4–C42–C43 170.9(11), C30–C31–C32 178.4(12), C42–C43–C44 177.7(11), D–Co–D 176.2(2), average D–Fe–D 178.3 (D denotes the centroid of the η4- or η5-coordinated ligand).
The reaction of 1 with 2 (see above) leads not only to the formation of 3a,b, also dicobalt species 4a,b could be isolated in low yield according to further reaction of one of the two alkynyl functionalities in 3 with 1 and 2 (Figure C1). However, only a few crystals of 4a could be isolated at ambient temperature from a n-hexane/dichloromethane mixture (ratio 3:1, v/v) containing isomers 4a,b. Compounds similar to 4a,b together with a proposed reaction mechanism have recently been published by Mandapati et al.[C36]
Formation of brown single crystals of 4a allowed its structural characterization by single-crystal X-ray diffraction (Figure C3). Organometallic 4a possesses a twisted
conformation with C2 symmetry (Figure C3). In contrast, isomer 4b possesses planar
chirality and is obtained as a racemic mixture. For the ferrocenyl and cobalt C5H5 ligands, seven signals are found at δ = 4.08, 4.14, 4.18, 4.31, 4.32 (each 5 H), 4.34 (10 H), and 4.39 (5 H) ppm, indicating that overlapping signals are present as can be concluded from the
1 signal ratio. The H NMR spectrum of 4b contains eleven resonances for the C5H4 protons,
from which one appears as doublet-of-doublets (JH,H = 3.8, 2.0 Hz, 4 H) and ten as multiplets (2 H each) (see the Experimental Section and the Supporting Information).
Figure C3. ORTEP diagram (30 % probability level) of the molecular structure of 4a. Hydrogen atoms and the disordered dichloromethane molecule as packing solvent have been omitted for clarity. Symmetry code for “A” labelled atoms: –x + 1, y, –z + ½. Selected bond lengths (Å) and angles (°): C11–C12 1.210(5), C33– C34 1.452(5), C33–C36 1.465(5), C34–C35 1.470(5), C35–C36 1.470(5), C35–C35A 1.459(7), Co–D(C5H5) 1.6831(4), Co–D(C4) 1.6944(4), average Fe–D 1.653; C10–C11–C12 176.1(4), C11–C12–C33 175.4(4), D–Co– D 178.05(3), average D–Fe–D 178.8 (D denotes the centroid of the η4- or η5-coordinated ligand).
68 The C≡C stretching vibration of the cyclobutadiene FcC≡C substituents is shifted toward lower frequencies with respect to the free acetylene (for 1,4-diferrocenylbuta- diyne (1) ν(C≡C) 2100 cm–1[C41]). In compound 3a, this vibration is found at 2195 cm–1 as a very weak absorption, whereas in 4b it could not be detected. Similar results were
5 4 –1 observed for compounds Co[η -C5H4C(O)OMe][η -C4Ph3(C≡CPh)] (ν(C≡C) 2186 cm ) and
5 4 –1 [C36] Co[η -C5H4C(O)OMe][η -C4Ph2(C≡CPh)2] (ν(C≡C) 2190 cm ). Organometallic com- pounds 6 and 7 (Figure C1) were successively obtained from 1 and 2 by the formation of a cobalt cyclobutadiene species in situ with subsequent CO insertion into a Co–C bond.[C42,43] Reductive elimination gave the respective cyclopentadienone cobalt compounds 6 and 7 (Figure C1).[C35,37] These species could be obtained in significantly higher yields when the reaction of 1 with 2 was carried out in the presence of carbon monoxide (see above). However, the insertion of a second CO unit was not observed under the reaction conditions applied. Cobalt-coordinated cyclopentadienones have been known since the early work of Rausch and Genetti; namely, (η5-cyclopentadienyl)(η4-(tetraphenyl- cyclopentadienone)cobalt(I).[C35,40] In the following years, similar compounds with diverse functionalities at the cyclic core were prepared.[C44,45] The three isomers 6a–c were formed within the reaction of 1 with 2 and could be separated by column chromatography
(see the Experimental Section). The two symmetric (Cv) isomers 6b,c show, when
1 compared with planar-chiral 6a, fewer H NMR signals for the C5H5 groups present. The
1 H NMR spectra of 6b,c are characterized by three singlets related to the C5H5 protons, one signal for the two spectroscopically identical Fc units, one for the FcC≡C ligands, and one for the cobalt-bonded cyclopentadienyl moiety with half the intensity of the ferrocenyl building blocks. 1H NMR spectroscopy including NOESY experiments allowed 6b and 6c to be distinguished (see the Supporting Information, Figures CS35–CS37 and
CS41–CS43). Due to the chirality of isomer 6a, five spectroscopically inequivalent C5H5 proton signals were observed at δ = 4.20, 4.23, 4.32, 4.42 (ferrocenyl), and 4.55 (cobalt) ppm. The elucidation of the structure of 6a and assignment of each hydrogen atom to the signals of the 1H NMR spectrum was achieved based on 2D COSY and NOESY NMR spectroscopic studies (see the Supporting Information, Figures CS28–CS30).
IR and 13C{1H} NMR spectroscopy could also be used to characterize the cyclopentadienone species 6a–c and 7, since the C≡C and CO fragments give absorptions and resonances in a characteristic range. In contrast to the cyclobutadiene-based complexes 3 and 4, the IR spectra of 6a–c show ν(C≡C) vibrations at 2210 cm–1 of medium intensity. For the mixed cyclobutadiene-cyclopentadienone compound 7,
69 however, the appropriate band at 2210 cm–1 is weak. There is also, as expected, a strong ν(CO) band present at ca. 1600 cm–1 in 6a–c, whereas the one for 7 is found at 1615 cm–1 (see the Experimental Section), which is typical for this type of sandwich compounds.[C44,45] In the 13C{1H} NMR spectra of 6 and 7, a characteristic resonance signal at δ = 156.1 (6a), 158.2 (6b), 154.8 (6c), and 158.2 (7) ppm appeared, which can be assigned to the carbon atom of the carbonyl ligand.[C46] Planar-chiral 6a shows for the
ferrocenyl C5H4 units twelve carbon resonance signals, four partially overlapping, for the
5 5 Fe(η -C5H5) and one related to the Co(η -C5H5) building block. In contrast, the
5 symmetrical isomers 6b,c are characterized by nine carbon signals (six for Fe(η -C5H4),
5 5 two for Fe(η -C5H5), and one for Co(η -C5H5)). The resonance signals related to the C≡C carbon atoms are located at δ = 95.2, 96.2 (6a), 90.5, 96.4 (6b) and 81.7, 95.7 (6c) ppm (see the Experimental Section).
The formation of compounds 5a,b (in Chapter D compounds 3a,b) including cobalt- assisted cyclotrimerization and subsequent ring-closing C–H activation reactions has been discussed previously.[C34] Within these studies, we were able to isolate and characterize a third isomer (compound 5c) (Figure C1) (see the Experimental Section). The formation of this compound is based on the mechanism reported for 5a,b (in Chapter D compounds 3a,b) with the generation of a symmetric type A molecule in situ (for a more detailed discussion see ref. [C34]), and hence 5c is formed by a threefold C–H activation and cyclization reaction of intermediate B (Scheme C1).
Scheme C1. Formation of 5a–c from 1 and 2 via intermediates A and B. For a detailed mechanism of the formation of 5a,b see reference [C34] (in Chapter D compounds 3a,b).
70 Compound 5c was identified by 1H NMR spectroscopy (see the Supporting Information, Figures CS21–CS26). Three individual resonance signals are found for the chemically inequivalent C=CHFc protons at δ = 8.01, 7.94, and 7.78 ppm (see the Supporting Information, Figure CS27). The cyclopentadienyl groups of 5c, in contrast to those of 5a,b, (in Chapter D compounds 3a,b) show resonance signals at δ = 4.10, 4.18, 4.20, 4.24, 4.27, and 4.39 ppm, as a result of the asymmetric character of this isomer. In comparison to
[C34] 13 1 5 5a,b, the C{ H} NMR spectrum of 5c is more complex. The Fe(η -C5H5) carbon signals of the Fc substituents are found at δ = 71–72 ppm, and those for the 1,2-functionalized ferrocenyl groups at δ = 69–70 ppm. The characteristic C=CHFc carbon signals, found for 5a,b at δ ≈ 133 ppm,[C34] are shifted upfield in 5c and are observed at δ = 122.2, 123.1, and 124.0 ppm (see the Supporting Information). The IR spectra of 5a–c are characterized by absorptions at 3090, 1460, 1105, 1000, and 818 cm–1 (see the Supporting Information, Figure CS3).
2.2 Solid-State Structures
The molecular structures of 3a,b, 4a, 6a, and 7 in the solid-state have been determined by single crystal X-ray diffraction analysis. The corresponding molecular structures along with selected bond lengths (Å) and bond angles (°) are depicted in Figures C2 (3a,b), C3 (4a), C4 (6a) and C5 (7). In the case of 3a, the asymmetric unit comprises two crystallographically independent molecules of 3a, denoted as 3aA (containing Co1) and 3aB (containing Co2). Related structural features of 3aA and 3aB show marginal differences only. Therefore, exclusively 3aA is displayed and discussed. The crystal and structure refinement data are summarized in Table CS1 (see the Supporting Information). The respective compounds crystallize in the triclinic space group P–1 (3a), the monoclinic space groups P21/c (6a), P21/n (7) and C2/c (4) and the orthorhombic space group
P212121 (3b).
All compounds are characterized by a central tetrasubstituted cyclobutadiene (3aA,b, 4a) or cyclopentadienone entity (6a, 7), which are η4-coordinated to a cobalt cyclopentadienyl fragment resulting in a sandwich-type building block. For the latter two compounds, this is accomplished by a deviation of the position of the carbon atom of the carbonyl group of 0.155(8) (6a) and 0.212(4) Å (7) from the C4 plane. The ferrocenyl ligands display an eclipsed conformation; except for 4a for which two ferrocenyl groups
71 (Fe1: 29.0(3) °; Fe2: (20.8(3) °) adopt a staggered conformation. The cyclobutadiene- or cyclopentadienone-bonded ferrocenyl groups are anti-oriented with respect to the cobalt cyclopentadienyl fragment. For the ferrocenylethynyl substituents syn (3b, 4a) and anti (3aA, 6a) orientations as well as arrangements between these two extremes (3b, 6a) are observed. Due to steric hindrance the two η4-coordinated core moieties in 4a and 7 are rotated by 56.4(2) and 65.9(2) °, respectively, towards each other.
Figure C4. ORTEP diagram (30 % probability level) of the molecular structure of 6a. Hydrogen atoms and the two dichloromethane molecules as packing solvents have been omitted for clarity. Selected bond lengths (Å) and angles (°): C6–O1 1.240(6), C6–C7 1.463(7), C6–C10 1.472(7), C7–C8 1.439(7), C8–C9 1.452(7), C9– 10 1.441(7), C11–C12 1.207(8), C33–C34 1.190(7), Co–D(C5H5) 1.6659(6), Co–D(C4) 1.6564(6), average Fe– D 1.655; O1–C6–C7 127.2(4), O1–C6–C10 128.7(4), C7–C6–C10 103.8(4), C7–C11–C12 174.9(5), C9–C33– C34 176.5(5), C11–C12–C13 174.6(5), C33–C34–C35 177.6(5), D–Co–D 172.40(5), average D–Fe–D 178.14 (D denotes the centroid of the η4- or η5-coordinated ligand).
Figure C5. ORTEP diagram (30 % probability level) of the molecular structure of 7. Hydrogen atoms, all unsubstituted cyclopentadienyl ligands and the three dichloromethane molecules as packing solvents have been omitted for clarity. Selected bond lengths (Å) and angles (°): C11–C12 1.197(4), C13–C14 1.469(4), C13–C16 1.463(4), C14–C15 1.456(4), C15–C16 1.470(4), C15–C42 1.470(4), C42–C43 1.434(4), C42–C46 1.478(4), C43–C44 1.451(4), C44–C45 1.443(4), C45–C46 1.475(4), C46–O1 1.242(3), C72–C73 1.194(4), Co1–D(C4) 1.6900(4), Co1–D(C5H5) 1.6698(4), Co2–D(C4) 1.6555(5), Co2–D(C5H5) 1.6685(5), average Fe–D 1.651; C6–C11–C12 176.2(3), C11–C12–C13 178.1(3), C42–C46–O1 128.5(3), C42–C46–C45 104.1(2), C44– C72–C73 176.5(3), C45–C46–O1 126.9(3), C72–C73–C74 174.6(3), D–Co1–D 178.41(3), D–Co2–D 172.81(3), average D–Fe–D 177.9 (D denotes the centroid of the η4- or η5-coordinated ligands.
72 The analysis of short ring interactions suggests the presence of T-shaped π-interactions for all compounds. For this reason, dimeric as well as polymeric structures are formed in the solid state. Graphical representations of these interactions as well as a summary of their geometrical details can be found in the Supporting Information (Figures CS52 - CS67, Table CS2).
2.3 Electrochemistry
The electrochemical properties of 3a, 5a,b[C34], 5c, 6a–c and 7 were studied using cyclic voltammetry (CV) and square-wave voltammetry (SWV) and by in situ UV/Vis/NIR spectroelectrochemistry (3a and 6a–c) (Figures C6 – C9 and CS68 – CS70; Tables C1 and C2). The electrochemical measurements were performed under argon in dichloromethane
n –1 [C23,25,47–59] solutions containing [ Bu4N][B(C6F5)4] (0.1 mol∙L ) as supporting electrolyte.
– The weak coordinating counter ion [B(C6F5)4] is known to stabilize highly charged species in solution. Furthermore, the low ion-pairing capabilities lead to a poor shielding of the electrostatic interactions among the redox-active sites, resulting in an increase of the observed redox splitting.[C59–62] The cyclic voltammograms were measured at a scan rate of 100 mV∙s–1 at 25 °C. All potentials are referenced to the FcH/FcH+ (FcH = Fe(η5-
[C63] C5H5)2) redox couple (E°′ = 0 mV) as recommended by IUPAC.
Molecules 3a and 6a–c show four individual, reversible one-electron events for each of the four redox-active ferrocenyl groups in both CV and SWV (Figure C6). In contrast, an
4 5 electrochemical study on similar complexes, i.e., [Co(η -C4Fc4)(η -C5H5)] in
n [C64,65] [ Bu4N][PF6] showed only three resolved redox processes, which is most likely
– + attributed to the use of [PF6] as counterion for the oxidized Fc groups.
The first and second redox processes in 3a and 6a–c are related to the butadiene- or cyclobutadienone-bonded ferrocenyl groups, whereas the third and fourth redox events can be assigned to a subsequent oxidation of the FcC≡C ferrocenyl functionalities.[C49,66] For 3a a potential difference between the first two redox processes of ΔE°' = 250 mV was found, which is much higher than the ΔE°' values between the second and third as well as the third and the fourth process (Table C1). The reason for the higher ΔE°' values may be (i) the smaller distance between the iron ions, which leads to electrostatic repulsion, (ii)
73 the different chemical environment of Fc and FcC≡C, and (iii) a participation of the ferrocenyl groups in electron-transfer interactions.
Figure C6. Voltammograms of 3a (2.2 mmol∙L–1) and 6a-c in dichloromethane solutions (1.0 mmol∙L–1) at 25 °C with a glassy-carbon working electrode vs FcH/FcH+. Supporting electrolyte 0.1 mol∙L–1 n [ Bu4N][B(C6F5)4]. Cyclic voltammograms (solid lines: scan rate 100 mV/s). Square-wave voltammograms (dotted lines: step height 25 mV, pulse width 5 s, amplitude 5 mV).
The redox processes in 6a–c shift to higher potentials with respect to 3a because of the electron-withdrawing carbonyl group in the η5-cyclopentadienone core moiety. The different substitution patterns in 6a–c have a high impact on the potential of the first oxidation. For example, 6b is first oxidized at a ferrocenyl unit in α position with respect to the carbonyl moiety, which causes a shift of E°' towards cathodic potentials (55 mV) as a result of the electron-withdrawing effect of the CO building block. In contrast, cyclopentadienones 6a and 6c are oxidized at a ferrocenyl unit in β position, where the electron-withdrawing effect is less prominent and hence the oxidation occurs at a more anodic potential (–35, –60 mV). However, ΔE°' is not a suitable value for the electronic delocalization within mixed-valent species.[C67] Predominantly, ΔE°' correlates nicely with the electronic coupling parameter.[C52,68,69] However, a high degree of electronic coupling was observed for species with a low redox splitting.[C41,70–74] Furthermore, there are class I compounds according to the classification of Robin and Day [C75] known, that show high ΔE°' values.[C5,27,76,77]
74 The cyclic voltammogram of 5c shows six partially overlapping, electrochemically reversible redox events (Figure C7). In comparison, complex 5a (see Chapter D compound 3a) shows six, while 5b (see Chapter D compound 3b) shows only four partially overlapping redox couples.[C34] The square-wave voltammogram of 5c illustrates that the oxidation of 5c to 5c2+ occurs in a very close potential range. The following oxidations are well separated. The decrease of the differential current (Figure C7) at higher potentials can probably be attributed to a decrease in the heterogeneous electron transfer from the analyte to the electrode surface caused by the decreasing solubility of the higher charged compounds.
Figure C7. Voltammograms of 5c in dichloromethane solutions (0.25 mmol∙L–1) at 25 °C using a glassy- + –1 n carbon working electrode vs FcH/FcH . Supporting electrolyte: 0.1 mol∙L [ Bu4N][B(C6F5)4]. Solid line: cyclic voltammogram (scan rate 100 mV/s). Dotted line: square-wave voltammogram (step height 25 mV, pulse width 5 s, amplitude 5 mV).
Figure C8. Voltammograms of 7 in dichloromethane solutions (1.0 mmol∙L–1) at 25 °C using a glassy-carbon + –1 n working electrode vs FcH/FcH . Supporting electrolyte: 0.1 mol∙L [ Bu4N][B(C6F5)4]. Solid line: cyclic voltammogram (scan rate 100 mV/s). Dotted line: square-wave voltammogram (step height 25 mV, pulse width 5 s, amplitude 5 mV).
75
The cyclic voltammogram of 7 shows six partially overlapping, electrochemically reversible redox events, whereas the oxidation from 73+ to 75+ consists of two individual one-electron processes with a very similar potential (ΔE°' = 45 mV, determined by the method according to Richardson and Taube[C78]) (Figure C8). Simulation of the peaks in SWV with six Gaussian-shaped curves of equal integrals revealed six one-electron redox events, one for each ferrocenyl unit present.
Table C1. Cyclic voltammetry data (potentials vs FcH/FcH+, scan rate 100 mV∙s–1 at a glassy-carbon –1 4 5 electrode of 1.0 mmol∙L solutions) of Co(η -C4Fc4)(η -C5H5) for comparison and 3a, 5a–c, 6a–c and 7 in –1 n anhydrous dichloromethane solutions containing 0.1 mol∙L of [ Bu4N][B(C6F5)4] as supporting electrolyte at 25 °C. All potentials are given in mV.
[a] [a] [a] [a] [a] [a] E1°' E2°' E3°' E4°' E5°' E6°' Compd. ΔE°'[c] [b] [b] [b] [b] [b] [b] (ΔEp) (ΔEp) (ΔEp) (ΔEp) (ΔEp) (ΔEp)
CoCp [d] -85 75 225 283 - - 160/150/58 (C4Fc4) 250/110/125 3a -95 (75) 155 (70) 265 (70) 390 (80) - -
865 175/50[g]/335 5a[e] -100 (68) 75 125 460 (66) 640 (67) (128)[f] /80/215 730 5b[e] -80 (60) 75 (84) 445 (70) - - 155/370/285 (110)[f] 90/95/295/ 5c[g] -90 0 95 390 620 850 230/230 6a -35 (50) 180 (70) 305 (70) 450 (70) - - 215/125/145
6b 55 (65) 170 (70) 280 (65) 470 (70) - - 115/110/190
6c -60 (70) 115 (70) 310 (80) 440 (80) - - 175/195/130 205/175/140/ 7[g] -130 75 250 390 435 785 45/350 th [a] En°' = Formal potential of n redox process. [b] ΔEp = Potential difference between anodic and cathodic peak potential. [c] ΔE°' = Potential difference between the two ferrocenyl-related redox processes. [d] –1 n Electrolyte: 0.1 mol∙L [ Bu4N][PF6] in CH2Cl2/CH3CN, see references [C64,65]. [e] Data were taken from reference [C34] (see also Chapter D, compounds 3a,b). [f] The poor solubility of the penta- and hexa- cationic species led to an increase of ΔEp. [g] Data determined from square-wave voltammetry.
2.4 Spectroelectrochemistry
To gain a deeper insight into the charge-transfer behavior of the mixed-valent species 3a+ (Figure C9) and 6a–c+ (Figures CS68 – CS70, see the Supporting Information) in situ UV/Vis/NIR measurements were carried out by a stepwise increase of the potential from –300 to 1100 mV (step heights: 25, 50 or 100 mV) vs Ag/AgCl in an optically transparent
76 thin layer electrochemistry (OTTLE) cell.[C79] Dichloromethane solutions containing either
–1 –1 n –1 3a (2.2 mmol∙L ) or 6a–c (1.0 mmol∙L ) and [ Bu4N][B(C6F5)4] (0.1 mol·L ) as electrolyte were used at 25 °C.
The neutral compound 3a does not show, as expected, any absorption in the NIR region. Oxidation of 3a to mixed-valent 3a+ (350 mV) leads to broad and intense absorptions between 900 and 3000 nm, showing typical characteristics of intervalence charge transfer transitions (IVCT) (Figure C9).[C1,66,75,80] In the UV/Vis region (250 – 750 nm) ferrocenyl-related excitations (MLCT/d-d) could be detected.[C25,55,81] The physical parameters have been determined by deconvolution using three Gaussian-shaped curves (Figure C9, Table C2). Monocationic 3a+ shows two IVCT absorptions, one at 7400 cm–1 (ε
–1 –1 –1 = 930 L∙mol ∙cm , Δ 1/2 = 5350 cm ), which is probably related to electronic interactions between the two Fc/Fc+ moieties across the cyclobutadiene unit and a
–1 –1 –1 –1 weaker absorption at 4800 cm (ε = 230 L∙mol ∙cm , Δ 1/2 = 2000 cm ) attributed to an interaction pathway between the Fc+ unit and the FcC≡C functionalities (Figure C9).[C34,45,49] Furthermore, a ligand-to-metal charge transfer band (LMCT) was observed at
–1 –1 –1 –1 + 2+ 3900 cm (ε = 580 L∙mol ∙cm , Δ 1/2 = 1200 cm ). Further oxidation of 3a to 3a leads to a decrease of the NIR absorptions and to an increase of intensity of the LMCT bands accompanied by a hypsochromic shift. Only one IVCT absorption was detected for
2+ –1 –1 –1 –1 3a (Figure C9) at 6100 cm (ε = 300 L∙mol ∙cm , Δ 1/2 = 3150 cm ), attributed to the charge transfer from the Fc+ to the FcC≡C functionalities. The shift to higher energy is the result of the lower electron density in the cyclobutadiene moiety induced by the two electron-withdrawing ferrocenium groups.[C34,45,49] Due to the characteristics of those charge-transfer excitations, including low intensity and the relatively high Δ 1/2, species 3a+ and 3a2+ can be classified as weakly coupled class II systems according to the Robin and Day classification.[C82] For 3a3+ no IVCT band was observed, indicating that the FeII/FeIII ions of the FcC≡C moieties are not electronically coupled.
The spectroelectrochemical measurements of the cyclopentadienones 6a–c indicate decomposition of the complexes during the stepwise oxidation (Figures CS68 – CS70, Supporting Information). The neutral species showed, as expected, no absorptions in the NIR region. During the oxidation process by stepwise increase of the potential to 1000 mV, no intervalence charge transfer absorption was observed. Subsequent reduction to – 200 mV shows an irreversible behavior, since the spectra in the UV/Vis region differ from the initial spectra (Figures CS68 – CS70).
77
Figure C9. Left: UV/Vis/NIR spectra of 3a at rising potentials (2.2 mmol∙L–1) vs Ag/AgCl: –300 to 350 mV (top), 350 to 425 mV (bottom). Middle: deconvolution of the NIR absorptions of in situ generated 3a+ at 350 mV (top) and 3a2+ at 425 mV (bottom) using three Gaussian-shaped functions. Measurement conditions: –1 n dichloromethane solutions at 25 °C, supporting electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4]). Arrows indicate increasing or decreasing as well as shifting absorptions. Right: simplified structure of 3a showing possible communication pathways between Fc+ and Fc units in mixed-valent 3a+ (top) and 3a2+ (bottom). Fc = Fe(η5- 5 5 C5H4)(η -C5H5); Cp = η -C5H5.
Table C2. NIR data of 3a+/3a2+.[a]
(cm–1) max Δ (Δ ) [b] (cm– Compound Transition 1/2 1/2 theo (cm–1) 1) (ε (L∙mol–1∙cm–1))
LMCT 3900 (580) 1200
3a+ IVCT 4800 (230) 2000 3330
IVCT 7400 (930) 5350 4130
LMCT 4000 (300) 1260
3a2+ IVCT 6100 (300) 3150 3750
LMCT 10150 (2500) 3650
–1 n [a] In dichloromethane containing 0.1 mol∙L [ Bu4N][B(C6F5)4] as supporting electrolyte at 25 °C. [b] 1/2 Calculated with equation (Δ 1/2)theo= (2310∙ max) according to the Hush relationship for weakly coupled systems.[C82]
78 3 Experimental Section
3.1 Instrumentation
1H NMR (500.3 MHz) and 13C{1H} NMR (125.8 MHz) spectra were recorded with a Bruker Avance III 500 spectrometer operating at 298 K in the Fourier transform mode. Chemical shifts (δ) are reported in ppm relative to tetramethylsilane using the solvent as
1 13 1 internal reference (CDCl3: H at 7.26 ppm and C{ H} at 77.16 ppm). IR spectra were recorded with FTIR Nicolet 200 equipment. The melting points of analytical pure samples (sealed off in nitrogen-purged capillaries) were determined with a Gallenkamp MFB 595 010 M melting-point apparatus and an Automated Melting Point Meter M5000 from A. Krüss Optronic. Microanalyses were performed with a Thermo FLASHEA 1112 Series instrument. High-resolution mass spectra were performed with a micrOTOF QII Bruker Daltonite workstation.
Suitable single crystals have been obtained from hexane/dichloromethane mixtures (ratio 3:1, v/v) containing the respective organometallic compound(s) at ambient temperature. Crystals of 3a, 4a, 6a and 7 were obtained in the form of 3a0.25CH2Cl2,
4aCH2Cl2, 6a2CH2Cl2 and 73CH2Cl2, whereby the dichloromethane molecules act as packing solvents only. Compound 3b crystallized without any packing solvent. Crystal data were collected with an Oxford Gemini S diffractometer using graphite- monochromatized Mo-Kα radiation (λ = 0.71073 Å; compounds 3a, 4a, 7) or Cu-Kα radiation (λ = 1.54184 Å; compounds 3b, 6a). The structures were solved by direct methods and refined by full-matrix least-squares procedures on F2 with SHELXL-2013.[C83] All non-hydrogen atoms were refined anisotropically and a riding model was employed in the treatment of all other hydrogen atoms. In case of 3a0.25CH2Cl2 the dichloromethane molecule is disordered along a crystallographic inversion center. In case of 4aCH2Cl2 the packing solvent is statistically disordered along a crystallographic inversion center. Analysis of π-π contacts has been carried out using PLATON.[C84] CCDC 1481829
(3a0.25CH2Cl2), 1481830 (3b), 1481831 (4aCH2Cl2), 1481832 (6a2CH2Cl2), and
1481833 (73CH2Cl2), contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre.
79 Electrochemical measurements were performed in anhydrous air free dichloromethane
n −1 solutions containing [ Bu4N][B(C6F5)4] (0.1 mol L ) as supporting electrolyte, which were conducted under a blanket of purified argon at 25 °C with a Radiometer Voltalab PGZ 100 electrochemical workstation interfaced with a personal computer. A three-electrode cell, featuring a Pt auxiliary electrode, a glassy-carbon working electrode (surface area 0.031
2 + −1 cm ), and an Ag/Ag (0.01 mol L AgNO3) reference electrode mounted on a Luggin capillary was used. The working electrode was pretreated by polishing on a Buehler microcloth first with a 1 μm and then with a 1/4 μm diamond paste. The reference
electrode was constructed from a silver wire inserted into a solution of AgNO3 (0.01 mol
−1 n −1 L ) and [ Bu4N][B(C6F5)4] (0.1 mol L ) in acetonitrile, in a Luggin capillary with a Vycor tip. This Luggin capillary was inserted into a second Luggin capillary with a Vycor tip filled
n −1 with a dichloromethane solution of [ Bu4N][B(C6F5)4] (0.1 mol L ). Successive experiments under the same experimental conditions showed that all formal reduction and oxidation potentials were reproducible within ±5 mV. Experimentally potentials were referenced against an Ag/Ag+ reference electrode but results are presented referenced
+ + against ferrocene (FcH/FcH couple = 220 mV vs. Ag/Ag , ΔEp = 61 mV) as an internal standard as required by IUPAC.[C63] When decamethylferrocene was used as an internal standard, the experimentally measured potential was converted into E vs. FcH/FcH+
+ + (under our conditions the Fc*/Fc* couple was at −614 mV vs. FcH/FcH , ΔEp = 60 mV).[C47] Data were then manipulated on a Microsoft Excel worksheet to set the formal redox potentials of the FcH/FcH+ couple to E°’ = 0.000 V. The cyclic voltammograms were typically taken after two scans and are considered to be steady-state cyclic voltammograms in which the signal pattern did not differ from that of the initial sweep.
Spectroelectrochemical UV/Vis/NIR measurements were performed in anhydrous
n −1 dichloromethane solutions containing [ Bu4N][B(C6F5)4] (0.1 mol L ) as the supporting electrolyte in an optically transparent thin-layer electrochemistry (OTTLE, quartz windows for UV/Vis/NIR)[C79] cell with a Varian Cary 5000 spectrophotometer (UV/Vis/NIR) at 25 °C. Between the spectroscopic measurements the applied potentials were increased stepwise by 25, 50 or 100 mV. At the end of the measurements the analyte was reduced at -300 mV for 40 min and an additional spectrum was recorded to establish the reversibility (or irreversibility) of the oxidations.
80 3.2 General Conditions
All reactions were carried out under argon by using standard Schlenk techniques. The drying of n-hexane, diethyl ether and dichloromethane was performed with an MBraun SPS-800 system (double column solvent filtration, working pressure 0.5 bar). Methanol was purified by distillation from magnesium. m-Xylene was degassed and purged with argon before its use as a reaction solvent.
3.3 Reagents
1,4-Diferrocenylbutadiyne (1) was synthesized according to a published procedure.[C85] Dicarbonyl(η5-cyclopentadienyl)cobalt (2) was purchased from commercial sources and was used as received. For the synthesis and analysis of molecules 5a,b see reference [C34] (in Chapter D as copounds 3a,b).
3.4 General Procedure - Reaction of 1 with 2
Compound 1 (0.750 g, 1.8 mmol) was dissolved in m-xylene (100 mL), and the solution was heated to 90 °C. Compound 2 dissolved in m-xylene (15 mL) was added dropwise in a molar ratio of 1:2 over 30 min. The reaction mixture was heated at 140 °C for 24 – 36 h, then cooled to ambient temperature. All volatiles were removed in vacuo, and the obtained crude material was purified by chromatography (column size: 3.5 x 22 cm; neutral alumina; n-hexane/dichloromethane 2:1 (v/v)). The polarity of the solvent was gradually increased (2:1 → 3:2 → 1:1 → 1:2), whereby seven fractions were collected. Fraction 1 (n-hexane/dichloromethane, 2:1 (v/v)) was bright yellow, fraction 2 (2:1) was yellow-orange, fraction 3 (2:1) was orange-red, fraction 4 (3:2) was red, fraction 5 (3:2) was pink, fraction 6 (1:1) was dark red-purple, fraction 7 (1:2) was dark brown. Each fraction was redissolved in dichloromethane (15 mL) and repeatedly purified by chromatography (neutral alumina; column size: 2.5 x 32 cm; unless different stated) as described below.
81 The first small, bright-yellow fraction containing impurities was discarded. The second yellow-orange fraction eluted with n-hexane/dichloromethane (ratio 2:1 (v/v)) contained unreacted starting material 1. The third orange-red fraction containing 3a,b, 4a,b was eluted with n-hexane/dichloromethane (ratio 2:1 (v/v)) and was collected in four parts: the first gave pure 3a, followed by mixtures of 3a,b and 4a,b and the last one pure 4b. A separation of 3b or 4a from the two mixtures was unsuccessful. The fourth red fraction was eluted with n-hexane/dichloromethane solvent mixtures of ratio 2:1 and 1:1 (v/v). This fraction contained 5a and 5b. The pink fifth fraction eluted with an n- hexane/dichloromethane mixture of ratio 3:2 (v/v)) was identified as 5c. The sixth dark- red-purple fraction eluted with n-hexane/dichloromethane (ratio 1:1 (v/v)) contained a mixture of the three isomers 6a‒c and compound 7. Isomer 6b and complex 7 were isolated on alumina (column-size: 2.5 x 32 cm; acetonitrile/dichloromethane, 1:1 (v/v)). The remaining mixture of isomers 6a and 6c was then separated on silica (column-size 2.5 x 22 cm; acetonitrile/dichloromethane, 1:1 (v/v)). All products were dried in vacuo.
3.4.1 Compound 3a
o 1 Yield: 38 %; m.p. 180 C (decomp.). H NMR (CDCl3): δ = 4.28 (s, 10 H, C5H5/Fc), 4.30 -
4.32 (m, 8 H, Hβ(C5H4/Fc), Hβ(C5H4/C≡CFc)), 4.34 (s, 10 H, C5H5/C≡CFc), 4.60 (s, 5 H,
C5H5/Co), 4.61 (pt, JHH = 1.80 Hz, 4 H, Hα(C5H4/C≡CFc)), 4.74 (pt, JHH = 1.80 Hz, 4 H,
13 1 Hα(C5H4/Fc)) ppm. C{ H} NMR (CDCl3): δ = 52.4 (Ci-Fc), 66.5 (Cα(C5H4/Fc)), 66.9 (Ci-Fc),
68.6 (Cβ(C5H4/Fc)), 69.0 (Cβ(C5H4/C≡CFc)), 69.7 (C5H5/Fc), 70.1 (C5H5/C≡CFc), 71.3
c c c (Cα(C5H4/C≡CFc)), 77.7 ( C4 or C≡C), 80.4 ( C4 or C≡C), 82.2 (C5H5/Co), 83.2 ( C4 or C≡C),
c 90.9 ( C4 or C≡C) ppm. IR (KBr): ṽ = 815 (s, broad, δ=CH), 1000 (s), 1020 (s), 1105 (s), 2195
-1 (vw, νC≡C), 3090 (m, ν=C-H) cm . C53H41CoFe4 ∙ ½CH2Cl2 (960.21 + ½ × 84.93): calculd. C
+ 64.09, H 4.22; found C 64.04, H 4.19. HRMS (ESI): calcd. for C53H41CoFe4 [M] 959.9938; found 959.9950.
82 3.4.2 Compound 3b
1 1 Yield: 3 % (estimated from H NMR). H NMR (CDCl3): δ = 4.25 (m, 2 Hβ(C5H4/Fc)), 4.27
(m, 4 H, Hβ(C5H4/C≡CFc)), 4.29 (s, 10 H, C5H5/Fc), 4.32 (s, 10 H, C5H5/C≡CFc), 4.33 (m, 2
H, Hβ(C5H4/Fc)), 4.55 (m, 2 H, Hα(C5H4/Fc)), 4.58 (m, 4 H, Hα(C5H4/C≡CFc)), 4.66 (s, 5 H,
13 1 C5H5/Co), 4.72 (m, 2 H, Hα(C5H4/Fc)) ppm. C{ H} NMR (CDCl3): δ = 56.5 (Ci-Fc), 66.8 (Ci-
Fc), 67.7 (C5H4/Fc), 67.9 (C5H4/Fc), 68.3 (C5H4/Fc), 68.4 (C5H4/Fc), 69.0 (C5H4/C≡CFc),
c c 69.7 (C5H5/Fc), 70.3 (C5H5/C≡CFc), 71.4 (C5H4/C≡CFc), 76.7 ( C4 or C≡C), 80.6 ( C4 or
c c C≡C), 82.5 ( C4 or C≡C), 82.6 (C5H5/Co), 91.9 ( C4 or C≡C) ppm.
3.4.3 Compound 4b
o 1 Yield: 1 %; m.p. 159 C. H NMR (CDCl3): δ = 4.08 (s, 5 H, C5H5), 4.14 (s, 5 H, C5H5), 4.18
(s, 5 H, C5H5), 4.29 (m, 2 H, C5H4), 4.31 (s, 5 H, C5H5), 4.32 (s, 5 H, C5H5), 4.34 (s, 10 H,
C5H5/Co), 4.37 (dd, J = 3.8, 2.0 Hz, 4 H, C5H4), 4.39 (s, 5 H, C5H5), 4.40 (m, 2 H, C5H4), 4.47
(m, 2 H, C5H4), 4.52 (m, 2 H, C5H4), 4.54 (m, 2 H, C5H4), 4.66 (m, 2 H, C5H4), 4.67 (m, 2 H,
13 C5H4), 4.70 (m, 2 H, C5H4), 5.23 (m, 2 H, C5H4), 5.53 (m, 2 H, C5H4) ppm. C NMR (CDCl3): δ
= 67.3 (C5H4), 67.5 (C5H4), 69.0 (C5H4), 69.1 (C5H4), 69.2 (C5H4), 69.2 (C5H4) 70.0 (C5H5),
70.1 (C5H5), 70.2 (C5H4), 70.2 (C5H4), 70.3 (C5H5/Co), 70.7 (C5H4), 70.7 (C5H4), 71.5 (C5H4),
- 72.3 (C5H4) ppm. IR (KBr): ṽ = 815 (s, δ=CH), 1000 (s), 1025 (s), 1105 (s), 3090 (s, ν=C-H) cm
1 + + . HRMS (ESI): calcd. for [M] 1501.9781, found 1501.9739; calcd for [M – 2(C5H5-Co)] 1254.0331, found 1254.0314.
3.4.4 Compound 5c
o 1 Yield: 1 %; m.p. 210 C (decomp.). H NMR (CDCl3): δ = 4.10 (s, 5 H, C5H5), 4.18 (s, 5 H,
C5H5), 4.20 (s, 5 H, C5H5), 4.24 (s, 5 H, C5H5), 4.27 (s, 5 H, C5H5), 4.39 (s, 5 H, C5H5), 4.44 (m, 1 H), 4.47 (m, 3 H), 4.48 (m, 2 H), 4.49 (m, 1 H), 4.52 (m, 1 H), 4.56 (m, 1 H), 4.72 (m, 1 H), 4.86 (m, 2 H), 4.90 (m, 2 H), 4.95 (m, 1 H), 4.98 (m, 1 H), 5.08 (m, 2 H), 5.11 (m, 1 H), 5.14 (m, 1 H), 5.19 (m, 1 H), 7.78 (s, 1 H, =CH–), 7.94 (s, 1 H, =CH–), 8.01 (s, 1 H, =CH–) ppm.
83 13 1 C{ H} NMR (CDCl3): δ = 62.1 (CH), 62.2 (CH), 64.4 (CH), 65.3 (CH), 65.4 (CH), 66.5 (CH),
68.7 (CH), 69.2 (CH), 69.4 (CH), 69.5 (C5H5), 69.5 (C5H5), 69.6 (C5H5), 69.9 (CH), 70.3 (CH),
70.6 (CH), 70.8 (CH), 71.0 (C5H5), 71.1 (C5H5), 71.6 (C5H5), 122.2 (=CH–), 123.1 (=CH–),
124.0 (=CH–) ppm. IR (KBr): ṽ = 730 (m), 818 (s, δ=CH), 1000 (s), 1045 (m), 1105 (s), 1240
-1 (m), 1365 (w), 1410 (w), 1465 (w, νC-C), 1625 (m), 1730 (m), 3090 (w, ν=C-H) cm . HRMS (ESI): calcd for [M]+ 1254.0331, found 1254.0307, calcd for [MH]+ 1255.0351, found 1255.0372.
3.4.5 Compound 6a
o 1 Yield: 34 % (purged with CO); m.p. 142 C. H NMR (CDCl3): δ = 4.20 (s, 5 H,
C5H5/Fc(1)), 4.23 (s, 5 H, C5H5/Fc(2)), 4.31 (m, 7 H, C5H5/Fc(3), C5H4/Fc(3/4)), 4.42 (m, 6
H, C5H5/Fc(4), H(2/3/5/6)), 4.46 (m, 3 H, H(2/3/5/6), H(4)), 4.50 (m, 1 H, H(2/3/5/6)), 4.52 (m, 1 H,
H(2/3/5/6)), 4.55 (s, 5 H, C5H5/Co), 4.65 (m, 2 H, C5H4/Fc(3/4)), 4.76 (m, 2 H, C5H4/Fc(3/4)),
5.31 (m, 1 H, H(9/10/11/12)), 5.52 (m, 1 H, H(9/10/11/12)), 5.59 (m, 1 H, H(9/10/11/12)), 5.97 (m, 1
13 1 H, H(9/10/11/12)) ppm. C{ H} NMR (CDCl3): δ = 65.5 (Ci -Fc), 66.2 (Ci -Fc), 67.1 (C5H4), 69.0
(C5H4), 69.2 (C5H4), 69.3 (C5H4), 69.5 (C5H4), 69.6 (C5H4), 69.7 (C5H4), 69.90 (C5H4), 69.92
(C5H5/Fc(1)), 70.2 (C5H5/Fc(2-4)), 71.2 (C5H4), 71.3 (C5H4), 71.6 (C5H4), 71.7 (C5H4), 78.3
c c c c ( C4 or C≡C), 79.0 ( C4 or C≡C), 82.2 ( C4 or C≡C), 83.8 ( C4 or C≡C), 85.2 (C5H5/Co), 95.2
c c ( C4 or C≡C), 96.2 ( C4 or C≡C), 156.1 (C=O) ppm. IR (KBr): ṽ = 815 (s, broad, δ=CH), 999
-1 (s), 1025 (s), 1105 (s), 1595 (s, νCO), 2210 (m, νC≡C), 3090 (w, ν=C-H) cm . C54H41CoFe4O (988.24): calcd. C 65.63, H 4.18; found C 65.13, H 4.16. HRMS (ESI): calcd. for [M]+ 987.9887; found 987.9904.
3.4.6 Compound 6b
o 1 Yield: 8 % (purged with CO); m.p. 118 C. H NMR (CDCl3): δ = 4.15 (m, 2 H, C5H4/Fc),
4.24 (s, 10 H, C5H5/Fc), 4.30 (m, 2 H, C5H4/Fc), 4.31 (m, 4 H, C5H4/C≡CFc), 4.34 (s, 10 H,
C5H5/C≡CFc), 4.37 (m, 2 H, C5H4/Fc), 4.68 (m, 4 H, C5H4/C≡CFc), 4.76 (m, 2 H, C5H4/Fc),
13 1 4.93 (s, 5 H, C5H5/Co) ppm. C{ H} NMR (CDCl3): δ = 63.9 (Ci -Fc), 66.2 (Ci -Fc), 68.4
84 (C5H4/Fc), 68.6 (C5H4/Fc), 69.2 (C5H4/C≡CFc), 70.2 (C5H5/Fc), 70.4 (C5H5/C≡CFc), 71.0
c c (C5H4/Fc), 71.8 (C5H4/C≡CFc), 72.0 (C5H4/Fc), 79.0 ( C4 or C≡C), 82.1 ( C4 or C≡C), 85.1
c c (C5H5/Co), 90.5 ( C4 or C≡C), 96.4 ( C4 or C≡C), 158.2 (C=O) ppm. IR (KBr): ṽ = 820 (s,
-1 δ=CH), 1000 (s), 1025 (s), 1105 (s), 1600 (s, νCO), 2210 (m, νC≡C), 3090 (w, ν=C-H) cm .
C54H41Fe4CoO ∙ 2CH3CN (988.22 + 2 × 41.05): calcd. C 65.09, H 4.43; found C 65.03, H 4.44. HRMS (ESI): calcd. for [M]+ 987.9887; found 987.9883; calcd. for [MH]+ 988.9965; found 988.9915.
3.4.7 Compound 6c
o 1 Yield: 5 % (purged with CO); m.p. 111 C (110.6, 108.0, 113.5). H NMR (CDCl3): δ =
4.22 (s, 10 H, C5H5/Fc), 4.38 (s, 10 H, C5H5/C≡CFc), 4.40 (m, 6 H, C5H4/Fc, C5H4/C≡CFc),
4.44 (m, 2 H, C5H4/Fc), 4.50 (s, 5 H, C5H5/Co), 4.70 (m, 2 H, C5H4/C≡CFc), 4.72 (m, 2 H,
13 1 C5H4/C≡CFc), 5.28 (m, 2 H, C5H4/Fc), 5.86 (m, 2 H, C5H4/Fc) ppm. C{ H} (CDCl3): δ = 65.3
(Ci -Fc), 67.1 (C5H4/Fc), 68.8 (C5H4/Fc), 69.5 (C5H4/Fc), 69.60 (C5H4/C≡CFc), 69.62
(C5H4/C≡CFc), 69.9 (C5H5/Fc), 70.4 (C5H5/C≡CFc), 71.67 (C5H4/C≡CFc), 71.71
c c c (C5H4/C≡CFc), 71.9 (Ci -Fc), 78.3 ( C4/C≡C), 79.5 ( C4/C≡C), 81.7 ( C4/C≡C), 85.2
c (C5H5/Co), 95.7 ( C4/C≡C), 154.8 (C=O) ppm. IR (KBr): ṽ = 817 (s, δ=CH), 1005 (s), 1105 (s),
-1 1600 (s, νCO), 2210 (m, νC≡C), 3090 (w, ν=C-H) cm . C54H41Fe4CoO ∙ ½C6H14 (988.22 + ½ × 86.18): calcd. C 66.32, H 4.78; found C 65.93, H 4.83. HRMS (ESI): calcd. for [MH]+ 988.9965; found 988.9919.
3.4.8 Compound 7
o 1 Yield: 8 % (purged with CO); m.p. 170 C (decomp.); H NMR (CDCl3): δ = 3.52 (m, 1 H,
C5H4), 3.95 (m, 1 H, C5H4), 4.15 (m, 1 H, C5H4), 4.18 (s, 5 H, C5H5), 4.19 (m, 1 H, C5H4), 4.32
(m, 13 H, 2 C5H5, C5H4), 4.37 (s, 10 H, 2 C5H5), 4.41 (m, 1 H, C5H4), 4.47 (s, 10 H, C5H5), 4.49
(m, 2 H, C5H4), 4.58 (m, 1 H, C5H4), 4.65 (m, 2 H, C5H4), 4.68 (m, 2 H, C5H4), 4.81 (m, 2 H,
C5H4), 4.84 (m, 2 H, C5H4), 4.88 (m, 1 H, C5H4), 4.94 (s, 5 H, C5H5), 5.47 (m, 1 H, C5H4), 5.47
13 1 (m, 1 H, C5H4), 6.03 (m, 1 H, C5H4) ppm. C{ H} NMR (CDCl3): δ = 54.3, 63.8, 66.2, 66.4
85 (C5H4), 66.5 (C5H4), 67.67 (C5H4), 67.74, 68.0 (C5H4), 68.2 (C5H4), 68.4 (C5H4), 68.5 (C5H4),
68.7 (C5H4), 68.8 (C5H4), 68.9 (C5H4), 69.2 (C5H4), 69.50 (C5H4) 69.52 (C5H5), 69.57 (C5H5),
69.61 (C5H4), 69.7 (C5H4), 69.87 (C5H5), 69.92 (C5H4), 70.0 (C5H4), 70.1 (2 C5H5), 70.2
(C5H4), 70.5 (C5H4), 70.6 (C5H5), 70.8 (C5H4), 71.0 (C5H4), 71.2 (C5H4), 73.5, 73.6, 76.5, 78.8,
79.3, 79.5, 81.3, 81.4, 81.6, 83.2 (C5H4), 83.8 (C5H5/Co), 84.7 (C5H5/Co), 84.8, 85.0, 85.3
(C5H4), 91.8, 93.6, 96.5, 158.2 (C=O) ppm. IR (KBr): ṽ = 805 (s, δ=CH), 999 (s), 1025 (1075)
-1 (s,), 1105 (s), 1260 (s), 1615 (1620) (m, νCO), 1735 (s), 2210 (w, νC≡C), 3090 (w, ν=C-H) cm . HRMS (ESI): calcd. for [MH]+ 1530.9809; found 1530.9736.
4 Supporting information
Supporting information for this article (Infra-Red Spectra, NMR Spectra, Cyclic Voltammograms, Spectroelectrochemical data, Crystal and Intensity Collection Data) is available on the WWW under http://dx.doi.org/10.1002/ejic.201600848.
5 References
[C1] A. Hildebrandt, U. Pfaff, H. Lang, Rev. Inorg. Chem. 2011, 31, 111–141.
[C2] A. Hildebrandt, H. Lang, Organometallics 2013, 32, 5640–5653.
[C3] A. K. Diallo, J. C. Daran, F. Varret, J. Ruiz, D. Astruc, Angew. Chem. Int. Ed. 2009, 48, 3141; Angew. Chem. 2009, 121, 3187.
[C4] P. Aguirre-Etcheverry, D. O'Hare, Chem. Rev. 2010, 110, 4839–4864.
[C5] P. Mucke, R. F. Winter, K. Kowalski, J. Organomet. Chem. 2013, 735, 10–14.
[C6] A. Ceccon, S. Santi, L. Orian, A. Bisello, Coord. Chem. Rev. 2004, 248, 683–724.
[C7] S. Barlow, D. O'Hare, Chem. Rev. 1997, 97, 637–670.
[C8] C. Levanda, K. Bechgaard, D. O. Cowan, J. Org. Chem. 1976, 41, 2700–2704. [C9] K. Heinze, H. Lang, Organometallics 2013, 32, 5623–5625.
[C10] K. M. Kadish, Q. Y. Xu, J. M. Barbe, Inorg. Chem. 1987, 26, 2566–2568.
[C11] N. G. Connelly, W. E. Geiger, Chem. Rev. 1996, 96, 877–910.
86 [C12] D. Astruc, C. Ornelas, J. Ruiz, Acc. Chem. Res. 2008, 41, 841–856.
[C13] C. M. Casado, I. Cuadrado, M. Moran, B. Alonso, B. Garcia, B. Gonzalez, J. Losada, Coord. Chem. Rev. 1999, 185–186, 53–79.
[C14] P. J. Low, Dalton Trans. 2005, 2821–2824.
[C15] A. Aviram, M. A. Ratner, Chem. Phys. Lett. 1974, 29, 277–283.
[C16] C. S. Lent, B. Isaksen, M. Lieberman, J. Am. Chem. Soc. 2003, 125, 1056–1063.
[C17] M. D. Ward, Chem. Soc. Rev. 1995, 24, 121–134.
[C18] F. Barigelletti, L. Flamigni, Chem. Soc. Rev. 2000, 29, 1–12.
[C19] M. Akita, T. Koike, Dalton Trans. 2008, 3523–3530. [C20] N. Robertson, C. A. McGowan, Chem. Soc. Rev. 2003, 32, 96–103.
[C21] M. D. Rausch, F. A. Higbie, G. F. Westover, A. Clearfield, R. Gopal, J. M. Troup, I. Bernal, J. Organomet. Chem. 1978, 149, 245–264.
[C22] J. Kotz, G. Neyhart, W. J. Vining, M. D. Rausch, Organometallics 1983, 2, 79–82.
[C23] A. Hildebrandt, D. Schaarschmidt, R. Claus, H. Lang, Inorg. Chem. 2011, 50, 10623– 10632.
[C24] K. Kaleta, F. Strehler, A. Hildebrandt, T. Beweries, P. Arndt, T. Ruffer, A. Spannenberg, H. Lang, U. Rosenthal, Chem. Eur. J. 2012, 18, 12672–12680.
[C25] M. Speck, R. Claus, A. Hildebrandt, T. Ruffer, E. Erasmus, L. Van As, J. C. Swarts, H. Lang, Organometallics 2012, 31, 6373–6380.
[C26] A. Hildebrandt, D. Schaarschmidt, H. Lang, Organometallics 2011, 30, 556–563.
[C27] A. Hildebrandt, T. Ruffer, E. Erasmus, J. C. Swarts, H. Lang, Organometallics 2010, 29, 4900–4905.
[C28] M. Speck, D. Schaarschmidt, H. Lang, Organometallics 2012, 31, 1975–1982.
[C29] Y. Yu, A. D. Bond, P. W. Leonard, U. J. Lorenz, T. V. Timofeeva, K. P. C. Vollhardt, G. D. Whitener, A. A. Yakovenko, Chem. Commun. 2006, 2572–2574.
[C30] A. K. Diallo, C. Absalon, J. Ruiz, D. Astruc, J. Am. Chem. Soc. 2011, 133,629–641.
[C31] Y. Yu, A. D. Bond, P. W. Leonard, K. P. C. Vollhardt, G. D. Whitener, Angew. Chem. Int. Ed. 2006, 45, 1794–1799; Angew. Chem. 2006, 118, 1826.
[C32] M. J. Eichberg, B. Kayser, P. W. Leonard, O. Š. Miljanić, T. V. Timofeeva, K. P. C. Vollhardt, G. D. Whitener, A. Yakovenko, Y. Yu, Inorg. Chim. Acta 2011, 369, 32–39.
[C33] N. Singh, A. J. Elias, J. Chem. Sci. 2011, 123, 853–860. [C34] G. Filipczyk, A. Hildebrandt, U. Pfaff, M. Korb, T. Ruffer, H. Lang, Eur. J. Inorg. Chem. 2014, 4258–4262.
[C35] M. D. Rausch, R. A. Genetti, J. Org. Chem. 1970, 35, 3888–3897.
87 [C36] P. Mandapati, N. Singh, D. Kumar, A. J. Elias, J. Organomet. Chem. 2012, 716, 208– 215.
[C37] H. V. Nguyen, M. R. Yeamine, J. Amin, M. Motevalli, C. J. Richards, J. Organomet. Chem. 2008, 693, 3668–3676.
[C38] N. Singh, A. Elias, Dalton Trans. 2011, 40, 4882–4891.
[C39] P. R. Chopade, J. Louie, Adv. Synth. Catal. 2006, 348, 2307–2327.
[C40] M. D. Rausch, R. A. Genetti, J. Am. Chem. Soc. 1967, 89, 5502–5503.
[C41] A. Donoli, A. Bisello, R. Cardena, A. Ceccon, M. Bassetti, A. D'Annibale, C. Pasquini, A. Raneri, S. Santi, Inorg. Chim. Acta 2011, 374, 442–446.
[C42] Z. Nagy-Magos, G. Bor, L. Marko, J. Organomet. Chem. 1968, 14, 205–209.
[C43] F. Calderazzo, Angew. Chem. Int. Ed. Engl. 1977, 16, 299–311; Angew. Chem. 1977, 89, 305.
[C44] A. Clearfield, M. D. Rausch, F. A. Higbie, I. Bernal, J. Organomet. Chem. 1977, 135, 229–248.
[C45] M. D. Rausch, I. Bernal, B. R. Davies, A. Siegel, F. A. Higbie, G. F. Westover, J. Coord. Chem. 1973, 3, 149–159.
[C46] G. Schaefer, D. B. Werz, T. H. Staeb, R. Gleiter, F. Rominger, Organometallics 2005, 24, 2106–2113.
[C47] A. Nafady, W. E. Geiger, Organometallics 2008, 27, 5624–5631.
[C48] J. M. Speck, M. Korb, A. Schade, S. Spange, H. Lang, Organometallics 2015, 34, 3788– 3798.
[C49] U. Pfaff, G. Filipczyk, A. Hildebrandt, M. Korb, H. Lang, Dalton Trans. 2014, 43, 16310–16321.
[C50] S. W. Lehrich, A. Hildebrandt, M. Korb, H. Lang, J. Organomet. Chem. 2015, 792, 37– 45.
[C51] S. W. Lehrich, A. Hildebrandt, T. Ruffer, M. Korb, P. J. Low, H. Lang, Organometallics 2014, 33, 4836–4845.
[C52] J. M. Speck, M. Korb, T. Ruffer, A. Hildebrandt, H. Lang, Organometallics 2014, 33, 4813–4823.
[C53] U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Ruffer, P. J. Low, H. Lang, Organometallics 2013, 32, 6106–6117.
[C54] D. Miesel, A. Hildebrandt, M. Korb, P. J. Low, H. Lang, Organometallics 2013, 32, 2993–3002.
[C55] U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Hahn, S. Liebing, J. Kortus, H. Lang, Organometallics 2012, 31, 6761–6771.
[C56] D. Miesel, A. Hildebrandt, M. Korb, D. Schaarschmidt, H. Lang, Organometallics 2015, 34, 4293–4304.
88 [C57] D. Miesel, A. Hildebrandt, M. Korb, H. Lang, J. Organomet. Chem. 2016, 803, 104–110.
[C58] D. Schaarschmidt, A. Hildebrandt, S. Bock, H. Lang, J. Organomet. Chem. 2014, 751, 742–753.
[C59] W. E. Geiger, F. Barriere, Acc. Chem. Res. 2010, 43, 1030–1039.
[C60] F. Barriere, W. E. Geiger, J. Am. Chem. Soc. 2006, 128, 3980–3989.
[C61] H. J. Gericke, N. I. Barnard, E. Erasmus, J. C. Swarts, M. J. Cook, M. A. S. Aquino, Inorg. Chim. Acta 2010, 363, 2222–2232.
[C62] R. J. LeSuer, C. Buttolph, W. E. Geiger, Anal. Chem. 2004, 76, 6395–6401.
[C63] G. Gritzner, J. Kuta, Pure Appl. Chem. 1984, 56, 461–466.
[C64] J. Jiao, G. J. Long, F. Grandjean, A. M. Beatty, T. P. Fehlner, J. Am. Chem. Soc. 2003, 125, 7522–7523.
[C65] J. Jiao, G. J. Long, L. Rebbouh, F. Grandjean, A. M. Beatty, T. P. Fehlner, J. Am. Chem. Soc. 2005, 127, 17819–17831.
[C66] T. Bobula, J. Hudlicky, P. Novak, R. Gyepes, I. Cisařova, P. Štěpnička, M. Kotora, Eur. J. Inorg. Chem. 2008, 3911–3920.
[C67] R. F. Winter, Organometallics 2014, 33, 4517–4536.
[C68] S. V. Lindeman, S. V. Rosokha, D. Sun, J. K. Kochi, J. Am. Chem. Soc. 2002, 124, 843– 855.
[C69] A. Hildebrandt, H. Lang, Dalton Trans. 2011, 40, 11831–11837.
[C70] S. Zališ, R. F. Winter, W. Kaim, Coord. Chem. Rev. 2010, 254, 1383–1396.
[C71] J. Maurer, B. Sarkar, B. Schwederski, W. Kaim, R. F. Winter, S. Zalis, Organometallics 2006, 25, 3701–3712.
[C72] A.-C. Ribou, J.-P. Launay, M. L. Sachtleben, H. Li, C. W. Spangler, Inorg. Chem. 1996, 35, 3735–3740.
[C73] A. Donoli, A. Bisello, R. Cardena, C. Prinzivalli, S. Santi, S. Chimiche, Organometallics 2013, 32, 1029–1036.
[C74] H. H. Shah, R. A. Al-Balushi, M. K. Al-Suti, M. S. Khan, C. H. Woodall, K. C. Molloy, P. R. Raithby, T. P. Robinson, S. E. C. Dale, F. Marken, Inorg. Chem. 2013, 52, 4898–4908.
[C75] M. B. Robin, P. Day, Adv. Inorg. Chem. Radiochem. 1968, 10, 247–422.
[C76] P. Mucke, M. Linseis, S. Zališ, R. F. Winter, Inorg. Chim. Acta 2011, 374, 36–50.
[C77] P. Mucke, R. F. Winter, I. Novak, K. Kowalski, J. Organomet. Chem. 2012, 717, 14–22.
[C78] D. E. Richardson, H. Taube, Inorg. Chem. 1981, 20, 1278–1285.
[C79] M. Krejčik, M. Danek, F. Hartl, J. Electroanal. Chem. 1991, 317, 179–187.
[C80] A. Heckmann, C. Lambert, Angew. Chem. Int. Ed. 2012, 51, 326–392; Angew. Chem. 2012, 124, 334.
89 [C81] Y. Zhu, M. O. Wolf, J. Am. Chem. Soc. 2000, 122, 10121–10125.
[C82] N. S. Hush, Electrochim. Acta 1968, 13, 1005–1023.
[C83] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[C84] A. L. Spek, Acta Crystallogr., Sect. D Biol. Crystallogr. 2009, 65, 148–155.
[C85] M. Rosenblum, N. Brawn, J. Papenmeier, M. Applebaum, J. Organomet. Chem. 1966, 6, 173–180.
90 CHAPTER D Combining Cobalt-Assisted Alkyne Cyclotrimerization and Ring Formation through C–H Bond Activation: A “One-Pot” Approach to Complex Multimetallic Structures
G. Filipczyk, A. Hildebrandt, U. Pfaff, M. Korb, T. Rüffer, H. Lang, Eur. J. Inorg. Chem. 2014, 4258–4262.
Compounds 4, 11 and 12 were synthesized and caracterised by Ulrike Pfaff. All other described products were synthesized and characterized by the author. The crystal X-ray structure data were collected, processed and discused by Tobias Rüffer and Marcus Korb. The (spectro)electrochemical experiments were conducted by the author. The results were consulted with Alexander Hildebrandt.
1 Introduction
Perferrocenylated super-crowded cyclic and heterocyclic structures have drawn rising attention during recent years as, besides the attractive molecular structure, these compounds possess interesting electrochemical and spectroscopic properties.[D1] Examples of this family of molecules are given by Vollhardt’s hexaferrocenyl benzene
5 5 [D2] {Fc6C6; Fc = Fe(η -C5H4)(η -C5H5)} , pentaferrocenyl cyclopentadienyl manganese
5 [D3] tricarbonyl [Mn(η -Fc5C5)(CO)3] and tetraferrocenyl(cyclopentadiene) iron tricarbonyl
5 [D4a] [Fe(η -Fc5C5)(CO)3] Rausch’s tetraferrocenyl cyclobutadiene cyclopentadienyl cobalt
4 5 [D4b] [Co(η -Fc4C4)(η -C5H5)], as well as perferrocenylated heterocycles of type Fc4C4E (E =
[D5] S, O, NMe, NPh, ZrCp2) from our research group. The crowded nature of the sterically demanding ferrocenyl groups at the respective ring systems is highlighted, for example, by a distortion of the cyclic unit as demonstrated for Fc6C6 by single crystal X-ray
[D2] 5 [D3a] diffraction analysis. In the case of Fc4C4NPh, Fc6C6 and [Mn(η -Fc5C5)(CO)3] rotation barriers for the individual ferrocenyl groups have been determined.[D2,3a,5] The multiple ferrocenyl units within perferrocenylated cycles and heterocycles additionally allow the investigation of their electrochemical behaviour and electron-transfer properties among the ring systems and between the ferrocenyl/ferrocenium units within a partly oxidized
n+ mixed-valent oxidation state, that is [Fc4C4NPh] (n = 1, 2, 3).
91 Herein, we present the straightforward, consecutive formation of a novel hexaferrocenyl benzene compound by [2+2+2] cyclotrimerization and ring formation through C–H bond activation reactions starting with 1,4-diferrocenylbutadiyne as the only
substrate in a “one-pot” synthetic method by applying [CoCp(CO)2] in either stoichiometric or substoichiometric amounts.
2 Results and Discussion
Organometallic compounds 3a/3b were accessible in a straightforward reaction of
FcC≡C–C≡CFc (1) with CoCp(CO)2 (2, 0.33 equiv.) in boiling m-xylene (Scheme D1). After appropriate workup, title complexes 3a/3b could be isolated as red crystals (see the Supporting Information for experimental details). Organometallic 3 exists as two isomers,
a C1 symmetric compound (for 3a) and a C3 symmetric compound (for 3b). Two of the 1,2- substituted ferrocenyl groups in 3a are oriented in the same direction, whereas the third
one is oriented in the opposite direction. In C3-symmetric 3b, all of the 1,2-disubstituted ferrocenyl units possess the same stereochemistry (Scheme D1). The asymmetry of isomer 3a causes a more complex NMR spectrum for the six ferrocenylcyclopentadienyl
moieties, whereas for C3-symmetric 3b only two representative resonances are observed. A similar behavior was found for the hydrogen atoms at the terminal C=C bond (for 3a, δ = 7.93 (1 H), 7.83 ppm (2 H); for 3b, δ = 7.83 ppm (3 H); see the Supporting Information).
Most likely the initial step in the synthesis of 3 is the trimerization of 1 across the C≡C unit to give 1,3,5-triferrocenyl-2,4,6-triethynylferrocenylbenzene (4, Scheme D3), a reaction that is well established for other alkynes.[D6] Organometallic 4 subsequently undergoes C–H activation followed by ring closure at the ferrocenyl-substituted
cyclopentadienyl (C5H4) unit to afford a five-membered ring (Schemes D1–3).
Scheme D1. Reaction of 1 with 2 (0.33 equiv) to give 3a/3b.
92 To confirm that the C–H activation and ring closure were indeed cobalt assisted, 1- ethynylferrocenyl-2-ferrocenyl benzene (8) was synthesized as a model compound and was subjected to reaction conditions similar to those described for the preparation of 3 (Scheme D2).
Br Fe Fe Br (i) (ii) (iii) Fe I Fe Fe
6 7 8 9
Scheme D2. Synthesis of 8 from 6 and 7 and its conversion to 9. Reaction conditions: (i) FcC≡CH (5), CuI, t t [D9] t NEt3, [Pd(PPh3)4]. (ii) BuLi, KO Bu, tetrahydrofuran, FcZnCl, [Pd(CH2C(CH3)2P( Bu)2)(µ-Cl)]2. (iii)
[CoCp(CO)2] (2), m-xylene).
[D7] Compound 8 was accessible by Sonogashira C,C crosscoupling of 1-Br-2-I-C6H4 (6) with FcC≡CH (5) to give 7, which was converted into 8 by subsequent Negishi C,C cross-
[D8] [D9] t [D11] coupling with ferrocenylzinc chloride by using [P( C4H9)2C(CH3)2CH2Pd(μ-Cl)]2 as the catalyst (Scheme D2). Complex 8 was successfully converted into 9 by addition of
[CoCp(CO)2] (2) in a 1:1 molar ratio to afford 9 in excellent yield (see the Supporting Information). Diferrocenyl 9 exists as two isomers [3:4 ratio E(9a)/Z(9b)] (Scheme D2). This differs from 3a/3b in which solely the Z isomer at the C=C bond was observed. Owing to steric hindrance of the 1,2-disubstitued ferrocenyl group at the central benzene ring of 3a/3b, the E isomer is less favored than the Z arrangement.
Given that the cobalt-assisted C–H activation and subsequent ring closure reaction forms the E isomer first,[D12] an E/Z isomerization step has to occur. Kwan and co-workers reported that isomerization of 1,2-dimethyldiferrocenylethene occurs in organic solvents and is enhanced during spectro-electrochemical measurements.[D13] Oxidation of the FeII center in vinylferrocenes facilitates isomerization of the C=C bond.[D14] In situ UV/Vis/NIR measurements showed, however, that the isomerization of 9a to 9b does not occur in the monocationic oxidation state but is solely observed for doubly oxidized 9a2+. Intervalence charge transfer (IVCT) absorptions for both isomers could be detected in singly oxidized 9a+ and 9b+; however, further oxidation led to isomerization, and hence, irrespective of the starting material, identical spectra were observed for 9a2+ and 9b2+. Subsequent reduction emphasized that 9a2+ was converted into 9b2+, as only characteristic spectra for 9b could be recorded (Supporting Information, Figures S58–S61). In addition, it was
93 shown that an excess amount of the silver salt [AgPF6] was also capable of facilitating the isomerization process of 9a to 9b (Supporting Information, Figure S62).
To prove the postulated mechanism for the formation of 3 via 1,3,5-triferrocenyl-2,4,6- triethynylferrocenylbenzene (4), we independently synthesized 4 by the reaction sequence shown in Scheme D3. Under typical Sonogashira reaction conditions, 2,4,6- trichloro-1,3,5-triiodobenzene (11) was treated with FcC≡CH (5, 3 equiv) in the presence of a palladium catalyst to give 11, which upon applying the Negishi protocol afforded 4. In
the final step, in the presence of [CoCp(CO)2] 4 was converted into 3a/3b in a yield of 52% (3a/3b = 13:1; Scheme D3, also see the Supporting Information).
Fc Fc Fe Fe I Fe Cl Cl Cl Cl Fe Fe HC (i) (ii) (iii) I I H C Cl Fc Cl Fc Fc Fc CH Fe Fe Fe Fe
11 12 4 3 3a / 3b = 13:1
t Scheme D3. Synthesis of 3 from 4. Reaction conditions: (i) FcC≡CH (5), CuI, NEt3, [PdCl2(PPh3)2]. (ii) BuLi, t [D9] t KO Bu tetrahydrofuran, FcZnCl, [Pd{CH2C(CH3)2P( Bu)2}(µ-Cl)]2. (iii) [CoCp(CO)2] (2), m-xylene.
This study confirms the postulated mechanism for the formation of 3 from 1 and 2 including cyclotrimerization, C–H activation, and ring formation through the in situ generation of 1,3,5-triferrocenyl-2,4,6-triethynylferrocenylbenzene (4). With its six redox-active ferrocenyl units, 3 belongs to the only rarely developed family of multiferrocenyl aromatic compounds. It is one of the few examples[D3] in which the
ferrocenyl moieties are either σ bonded through a C5H4 cyclopentadienyl unit or part of a
five-membered cycle including a C5H3 ferrocenyl substituent (Schemes D1–3).
X-ray diffraction studies of single crystals of 3a in the form of 3a·2CHCl3 and those of
3 3b in form of 3b· /16CH2Cl2 were performed to determine the molecular structure of both
3 compounds. The asymmetric unit of 3b· /16CH2Cl2 comprises one C1 symmetric molecule
1 of 3b, denoted as 3bA, together with /3 of a C3 symmetric molecule of 3b, denoted as 3bB. The molecular structures of 3a and 3bB are illustrated in Figure D1, which verify the above made statements on the asymmetric/symmetric appearance of 3. Ball-and-stick models of 3a and 3bB that display both molecules in a side view to visualize the different orientation of the 1,2-substituted ferrocenyl groups with respect to the central aromatic core are shown in Figures S32 for 3a and S33 for 3bB.
94
Figure D1. ORTEP diagram (25 % (3a) and 10 % (3bB) probability level) of the molecular structure of 3a (left) and 3bB (right). All hydrogen atoms and packing solvent molecules are omitted for clarity.
The electrochemical characteristics of 3a/3b and 9a/9b were determined by cyclic
–1 voltammetry (CV) and squarewave voltammetry (SWV) by using 0.1 mol·L CH2Cl2
n [D15] solutions of [ Bu4N][B(C6F5)4] as an electrolyte (Figure D2). Depending on the analyte concentration, five (1.0 mmol·L–1) or six (0.5 mmol·L–1) reversible ferrocenyl-based one- electron redox events were observed for 3a, whereas four reversible processes and one irreversible redox process were observed for 3b irrespective of the concentration applied (Table D1, Figure D2). In 3a, the second and third redox couples are partly superimposed. For 3b, these two oxidation processes form one broadened event that cannot be resolved. The poor solubility of 3a and 3b in high oxidation states cause a deposition on the electrode surface, and therefore, the redox events for the fifth and sixth oxidations are decreased in the observed current and show an increased ΔEp value (Figure D2).
The spectroscopic properties of 3a/3b and 9a/9b in different oxidation states were determined by UV/Vis/NIR measurements in an optically transparent thin layer electro- chemistry (OTTLE) cell at stepwise increased potentials from –200 to +600 mV (for 9a/9b) or to +1300 mV (3a/3b) (see the Supporting Information, Figures S46–S57). During these studies, compounds 3a/3b and 9a/9b were oxidized, and hence, the spectra of 3a/3bn+ (n = 0, 3, 6) as well as those of 9a/9bn+ (n = 0, 1, 2) were observed.
Neutral compounds 3a/3b and 9a/9b exhibit, as expected, no absorption in the NIR region. Upon subsequent oxidation, mixed-valent 3a/3b3+ and 9a/9b+ are formed, and hence, broad absorptions between λ = 1000 and 3000 nm were observed. However, further potential increases led to the oxidation of all the ferrocenyl units, and hence, no absorptions in the NIR region were found. To determine the physical parameters (ṽmax,
εmax, Δṽ½) of the respective spectral components, deconvolution of the NIR region was
95 performed by using three (for 9a/9b+) or four (for 3a/3b3+) Gaussian-shaped absorptions. This methodology allowed an almost exact overlay of the sum of those Gaussians with the experimental spectra. Compounds 3a/3b3+ are characterized by one
–1 LMCT (ligand-to-metal charge transfer) absorption with a maximum at ṽmax = 3700 cm ,
–1 two IVCT bands at ṽmax = 5500 and 7300 cm (Table D2, Figures S48 and S51), and a
–1 MLCT (metal-toligand charge transfer) excitation at ṽ = 1100 cm . The IVCT band at ṽmax = 5500 cm–1 showed charge-transfer excitations through a C=C bond that were similar to those within, for example, diferrocenylethylenes[D13,14,16] and, therefore, can be attributed to charge transfer between two neighboring ferrocenyl units through the ethenyl moiety. Given that this structural motif is found three times within the molecule, the intensity of this band is amplified by a factor of about three relative to the values reported in the
[D13,14,16] –1 literature. The second, much less intense IVCT band (ṽmax = 7300 cm ), which resembles absorptions also found in 1,3,5-triferrocenylbenzene, may be attributed to charge transfer through the benzene ring.[D17]
* 3a
*
3b
* 9a
* 9b
-0.8 -0.4 0.0 0.4 0.8 1.2 1.6 -0.4 0.0 0.4 0.8 1.2 1.6 Potential [V] vs FcH/FcH+ Potential [V] vs FcH/FcH+
Figure D2. Cyclic voltammograms (left) and Square Wave voltammograms (right) of compounds 3a,b (0.50 –1 –1 –1 n mmol·L ) and 9a,b (1.0 mmol·L ) in 0.1 mol·L solutions of [ Bu4N][B(C6F5)4] in dichloromethane as electrolyte, 25 °C, * = reference decamethylferrocene.
96 Table D1. Cyclic voltammetry data of 3a,b and 9a,b. Measurement conditions: Concentration 0.50 mmol·L–1 (3a,b) and 1.0 mmol·L–1 (9a,b), 25 °C, reference decamethylferrocene, electrolyte 0.1 mol·L–1 solution of n [ Bu4N][B(C6F5)4] in dichloromethane.
E°' (ΔE ) ΔE°' Compd. Wave p in mV in mV
1st –100 (68)
2nd 75 (-)a 175
3rd 125 (-)a 50b 3a 4th 460 (66) 335
5th 640 (67) 80
6th 865 (128)c 215
1st –80 (60)
2nd 75 (84) 155 3b 3rd 445 (70) 370
4th 730 (110)c 285
1st –90 (64) 9a 2nd 310 (66) 400
1st –70 (66) 9b 2nd 315 (88) 385
[a] Due to overlapof the events ΔEp could not be determined. [b] Determined by square wave voltammetry. [c] Poor solubility of the penta- and hexa-cationic species leads to an increase of ΔEp.
Table D2. Results of the deconvolution in the NIR region of the absorption spectra of 3a,b and 9a,b
εmax Type of ν Δν Compd. max (L mol-1 1/2 Transition (cm-1) (cm-1) cm-1)
LMCT 3690 2855 855 3a3+ IVCT 5450 5385 4400 IVCT 7290 360 1450
LMCT 3720 1250 850 3b3+ IVCT 5600 2600 4300 IVCT 7300 380 1400
LMCT 4000 350 640 9a+ IVCT 4940 1680 3720
LMCT 3700 410 910 9b+ IVCT 4500 1560 3770
Compounds 9a/9b+, in contrast to 3a3+ and 3b3+, are characterized by one LMCT and one IVCT transition (Table D2, Figures S54 and S57) with position and intensities typical
97 for mixed-valent diferrocenylethylenes.[D13,14,16] In all cases, the full-width at half maximum of the IVCT transitions exceeds the theoretical values according to Hush.[D18] This is explainable by solvent reorganization[D19] and confirms the classification of the intermetallic charge-transfer interactions as class II systems according to Robin and Day.[D20]
3 Experimental Section (Supporting information)
In this part presented is the Experimental Section from the Supporting information of this article. Complete Supporting information is available on the WWW under http://dx.doi.org/10.1002/ejic.201402659.
3.1 General Information
All reactions were carried out under an atmosphere of argon using standard Schlenk techniques. Tetrahydrofuran and n-hexane were purified by distillation from sodium/benzophenone ketyl, while diethyl ether was purified by distillation from sodium and methanol from magnesium. Dichloromethane and diisopropylamine were purified by distillation from calcium hydride.
3.2 Starting Materials
[S1] [S2] [S3] 1,4-Diferrocenylbutadiyne (1) , ethynyl ferrocene (5) , [ZnCl2∙2thf] (10) , 1,3,5-
[S4] n [S5] [S6] trichloro-2,4,6-triiodobenzene (12) , [ Bu4N][B(C6F5)4] , [PdCl2(PPh3)2] and
t [S7] [P( C4H9)2C(CH3)2CH2Pd(μ-Cl)]2 were prepared according to published procedures. Other reagents were obtained from commercial sources and used without further purification.
98 3.3 Synthesis of 3a and 3b from 2
0.750 g (1.8 mmol) of 1 was dissolved in 100 mL of m-xylene. After heating this
° solution to 80 C, [CpCo(CO)2] (2) (0.110 g, 0.6 mmol) dissolved in 15 mL of m-xylene was added drop-wise over 30 min. Afterwards, the reaction mixture was heated under reflux for 36 h and cooled to ambient temperature. All volatiles were removed with a rotary evaporator (50 °C). The obtained crude material was purified by column chromatogaphy (column-size: 3.5 x 22 cm; alumina; n-hexane/dichloromethane = 2:1 (v/v)). The polarity of the solvent was gradually increased (2:1 → 3:2 → 1:1 → 1:2), whereby seven fractions could be collected. Fraction 1 (n-hexane/dichloromethane = 2:1 (v/v)) – yellow, fraction 2 (2:1) – orange, fraction 3 (2:1) – orange-red, fraction 4 (3:2) – red, fraction 5 (3:2) – pink, fraction 6 (1:1) – dark red-purple, fraction 7 (1:2) – dark brown.
The 4th fraction was additionally purified by chromatography (column-size: 3.5 x 30 cm; alumina; n-hexane/dichloromethane = 2:1 (v/v)) and was identified as 3a. The 5th fraction was identified as 3b. The fractions 1 – 3 and 7 were mixtures of several products and at this point were not completely separated and identified.
3.3.1 Complex 3a:
(Fc1, Cpb) 2a 3
1a
4a
8 (Fc2, Cpd)
5a 7b (Fc2, Cpc) 6b 7b 6a
8 5b
4b 1b 3 2b 5b 6a 4b 2b 1b 8 3 7a (Fc1, Cpa)
(Fc1, Cpa) (Fc2, Cpe)
Yield: 50.4 mg, 0.0402 mmol, 7.2% based on 1. m.p. > 250 °C (decomp.). 1H NMR
(CD2Cl2): δ = 4.19 (s, 5H, C5H5(Cpe)), 4.21 (s, 5H, C5H5(Cpd)), 4.22 (s, 5H, C5H5(Cpc)), 4.36
(s, 5H, C5H5(Cpb)), 4.37 (s, 10H, 2C5H5(Cpa)), 4.49 - 4.52 (m, 3H3), 4.55 (pt, JHH = 2.40 Hz,
99 1H7a), 4.58 - 4.59 (m, 4H, 2H7b, 2H2b), 4.60 - 4.61 (m, 1H2a), 4.71 - 4.72 (m, 1H4b), 4.72 -
4.73 (m, 1H4b), 4.80 - 4.81 (m, 1H4a), 5.07 (d, JHH = 2.0 Hz, 1H8), 5.09 (d, JHH = 2.0 Hz, 1H8),
5.10 - 5.12 (m, 3H, 1H8, 2H6b), 5.14 - 5.15 (m, 2H, 1H6a, 1H1a), 5.18 - 5.19 (m, 1H1b), 5.21 -
13 1 5.22 (m, 1H1b), 7.82 (s, 1H5a), 7.83 (s, 1H5b), 7.94 (s, 1H5b) ppm. C{ H} NMR (CDCl3): δ =
64.2 (1C, H8C), 64.5 (1C, H8C), 65.1 (1C, H8C), 65.2 (1C, H6aC), 65.4 (1C, H6bC), 65.6 (1C,
H6bC), 68.9 (1C, H1bC), 69.1 (1C, H1a,bC), 69.9 - 70.1 (21C, 3H2C, 3H3C, 15(Cpa,b)), 70.8 (2C,
H4a,bC), 71.0 (5C, Cpe), 71.1 (1C, H4bC), 71.2 (5C, Cpd), 71.5 (5C, Cpc), 72.0 (2C, H7bC), 72.2
(1C, H7aC), 84.3 (2C, Fc1C), 84.4 (1C, Fc1C), 87.2 (1C, Fc2C), 87.4 (1C, Fc2C), 88.5 (1C, Fc2C),
89.5 (1C, Fc2C), 90.1 (1C, Fc2C), 90.2 (1C, Fc2C), 122.4 (1C, H5aC), 123.0 (1C, H5bC), 123.4
(1C, H5bC), 133.0 (1C, C6CCH), 133.3 (1C, C6CCH), 133.4 (1C, C6CCH), 135.3 (2C, C6CCH),
135.6 (1C, C6CCH), 137.2 (1C, C6CCH), 137.8 (1C, C6CCH), 138.2 (1C, C6CCH) ppm. UV/Vis/NIR: λ (ε) = 350 (sh), 500 (19110), 1060 (670) nm (L∙mol–1∙cm–1). IR (KBr): ṽ =
817 (s, broad, δ=C-H double), 999 (s), 1039 (m), 1056 (m), 1105 (s, νC-C), 1630 (m, broad),
–1 3090 (w, ν=C-H single) cm . C72H54Fe6 (1254.27): calcd. C 68.95, H 4.34; found C 68.93, H 4.48. HRMS (ESI): calcd for [M]+ 1254.0331; found 1254.0322.
3.3.2 Complex 3b:
5
1 (Fc2, Cp2)
2 4 6 8 3 (Fc1, Cp1) 7
Yield: 19.5 mg, 0.0155 mmol, 2.6% based on 1. m.p. > 250 °C (decomp.). 1H NMR
(CDCl3): δ = 4.23(s, 15H, 3C5H5 (Cp1)), 4.37 (s, 15H, 3C5H5 (Cp2)), 4.48 - 4.49 (m, 3H, H3),
4.52 (pt, JHH = 2.40 Hz, 3H, H7), 4.54 - 4.56 (m, 3H, H2), 4.80 - 4.81 (m, 3H, H4), 5.07 (m, 3H,
13 1 H1), 5.08 (m, 3H, H8), 5.12 (d, JHH = 2.0 Hz, 3H, H6), 7.83 (s, 3H, H5) ppm. C{ H} NMR
(CDCl3): δ = 64.9 (1C, HC8), 65.4 (1C, HC6), 68.8 (1C, HC1), 69.3 (1C, HC3), 69.4 (1C, HC2),
69.5 (15C, 3C5H5 (Cp1)), 70.1 (1C, HC4), 71.2 (15C, 3C5H5 (Cp2)), 71.3 (1C, HC7), 84.0 (3C,
100 Fc2C), 88.0 (3C, Fc1C), 89.5 (3C, Fc1C), 121.8 (1C, HC5), 132.7 (3C, C6CCH), 135.6 (3C,
C6CCH), 137.8 (3C, C6CCH) ppm. UV/Vis/NIR: λ (ε) = 350 (sh), 500 (12490), 1060 (1010)
–1 –1 nm (L∙mol ∙cm ). IR (KBr): ṽ = 818 (s, broad, δ=C-H double), 1105 (s, νC-C), 1261 (m), 1462
–1 (m), 1739 (s), 3090 (w, ν=C-H single) cm . C72H54Fe6 (1254.27): calcd. C 68.95, H 4.34; found C 68.60, H 4.72. HRMS (ESI): calcd for [M]+ 1254.0331; found 1254.0355.
3.4 Synthesis of 9a and 9b from 1-Ferrocenylethynyl-2-Ferrocenyl Benzene (8)
3.4.1 Synthesis of 1-Bromo-2-Ferrocenylethynyl Benzene (7)
2-Bromo-1-iodobenzene (6) (0.620 g, 2.20 mmol), [Pd(PPh3)4] (76.0 mg, 0.0660 mmol), [CuI] (21.0 mg, 0.110 mmol) and triethylamine (10 mL) were treated with a solution of FcC≡CH (0.460 g, 2.20 mmol) in 4.5 mL of triethylamine (added with a syringe) and the reaction mixture was stirred at ambient temperature for 2 h. Afterwards, the reaction mixture was poured into 50 mL of a saturated NH4Cl solution and the product was extracted with diethyl ether (3 x 50 mL). The extract was washed with brine and dried over Na2SO4. After evaporation to dryness, the crude product was transferred to a column packed with silica gel (column-size: 3.5 x 22 cm) and n-hexane/dichloromethane in the ratio of 3:1 (v/v) and eluted with the same solvent mixture. The first orange-brown fraction contained the title compound 7: 0.590 g (1.60 mmol, 73% based on 2-bromo-1- iodobenzene).
1
2
5‘ 3 6‘ 4 5 6
° 1 M.p. 105 C. H NMR (CDCl3): δ = 4.26 (pt, JHH = 1.84 Hz, 2H6), 4.28 (s, 5H, C5H5), 4.56 (pt,
JHH = 1.84 Hz, 2H5), 7.15 (td, JHH = 7.8 Hz, 1.7 Hz, 1H, H2), 7.26 (td, JHH = 7.6 Hz, 1.1 Hz, 1H,
H3), 7.51 (dd, JHH = 7.7 Hz, 1.6 Hz 1H, H4), 7.60 (dd, JHH = 8.1 Hz, 0.9 Hz, 1H, H1) ppm.
13 1 C{ H} NMR (CDCl3): δ = 64.7 (1C), 69.2 (2C, HC6), 70.2 (5C, Cp), 71.7 (2C, HC5), 84.3 (1C),
101 93.6 (1C), 125.3 (1C), 126.1 (1C), 127.1 (1C, HC3), 128.9 (1C, HC2), 132.5 (1C, HC1), 133.2
(1C, HC4) ppm. IR (KBr): ṽ = 760 (s), 815 (m, δ=C-H doule), 923 (m), 1000 (m), 1026 (m, ν=C-
Br), 1105 (m, νC-C), 1410 (w, νC-H), 1445 (m), 1486 (m, broad), 2224 (m, νC≡C), 3106 (w, ν=C-
–1 H single) cm . C18H13FeBr (365.05): calcd. C 59.22, H 3.59; found C 59.12, H 3.53. HRMS (ESI): calcd for [M]+ 363.9546, 363.9525; found 363.9572, 363.9550.
3.4.2 Synthesis of 1-Ferrocenylethynyl-2-Ferrocenyl Benzene (8)
Ferrocene (1.60 mmol 0.300 g) was dissolved in tetrahydrofuran (30 ml) at ambient temperature and tBuLi (3.20 mmol, 3.20 mL) in n-hexane was added dropwise at –70 °C followed by addition of KOtBu (0.140 mmol, 18.0 mg). The reaction mixture was stirred
for 1 h. [ZnCl2∙2thf] (10) (1.60 mmol, 0.450 g) in 15 mL of tetrahydrofuran was added with a syringe via a rubber septum and the reaction mixture was stirred at –70 °C for 1 h. After the reaction mixture was warmed to ambient temperature, 1-bromo-2-
t ferrocenylethynyl benzene (7) (0.520 g, 1.40 mmol) and [P( C4H9)2C(CH3)2CH2Pd(μ-Cl)]2 (0.0140 mmol, 9.80 mg) were added in a single portion, and the mixture was stirred at 50 °C for 4 h. All volatiles were removed with a rotary-evaporator. The crude product was transferred to a column packed with silica gel (column-size: 3.5 x 22 cm) and n- hexane/dichloromethane in the ratio of 9:1 (v/v) and eluted with the same solvent mixture. The second orange-yellow fraction contained the titled product 8: (0.200 g, 0.430 mmol, 30 % based on 7).
(Cp ) 2 6 6‘ 5 1 5‘
2
7‘ 3 ‘ 4 8 7 8
(Cp1)
° 1 M.p. 46.5 C. H NMR (CDCl3): δ = 4.15 (s, 5H, C5H5 (Cp2)), 4.27 (s, 5H, C5H5 (Cp1)), 4.27
(pt, JHH = 1.90 Hz, 2H, H8), 4.37 (pt, JHH = 1.90 Hz, 2H, H6), 4.54 (pt, JHH = 1.90 Hz, 2H, H7),
5.03 (pt, JHH = 1.90 Hz, 2H, H5), 7.15 (td, JHH = 7.5 Hz, 1.3 Hz, 1H, H3), 7.25 (td, JHH = 7.5 Hz,
102 1.3 Hz, 1H, H2), 7.46 (dd, JHH = 7.7 Hz, 1.1 Hz, 1H, H4), 7.60 (dd, JHH = 7.7 Hz, 1.1 Hz, 1H, H1)
13 1 ppm. C{ H} NMR (CDCl3): δ = 66.1 (1C), 68.7 (2C, HC6), 69.0 (2C, HC5), 69.1 (2C, HC8),
69.9 (5C, Cp1), 70.0 (5C, Cp2), 71.2 (2C, HC7), 85.0, 86.9, 92.3, 121.4, 125.7 (1C, HC3), 127.7
(1C, HC2), 128.9 (1C, HC1), 133.7 (1C, HC4), 140.5 ppm. IR (KBr): ṽ = 758 (s), 817 (s, broad
δ=C-H double), 923 (m), 1000 (s), 1031 (m), 1105 (s, νC-C), 1410 (w, νC-H), 1445 (w), 1487 (m),
–1 2225 (m, νC≡C), 3091 (w, ν=C-H single) cm . C28H22Fe2 (470.16): calcd. C 71.53, H 4.72; found C 71.25, H 4.65. HRMS (ESI): calcd. for [M]+ 470.0416; found 470.0475; calcd. for [MH]+ 471.0448; found 471.0461.
3.4.3 Synthesis of 9a and 9b from 8
The synthesis of 9a and 9b from 8 follows the same procedure as described for the preparation of 3a and 3b. 200 mg (0.430 mmol) of 8 reacted with 77.5 mg (0.430 mmol) of 2 in the molar ratio 1:1. The crude product was chromatographed (column-size: 2.0 x 35 cm; alumina) with a solvent mixture n-hexane/dichloromethane in the ratio of 9:1 (v/v).
The initial separation gave three fractions. Fraction 1 was identified as isomer 9a, fraction 2 was a mixture of both isomers 9a,b, which had to be repeatedly separated on the same column as above, until a full separation of the two isomers was achieved, and fraction 3 was identified as isomer 9b. The remaining brown fraction and the small dark green fraction, both remaining on the top of the column, were not soluble in any common solvents and were discarded.
Complex 9a: (Cp1)
(Cp2)
103
° 1 Yield: 37.5 mg (0.0798 mmol), 19% based on 8; m.p. 171 C; H NMR (CDCl3): δ = 3.91
(s, 5H, C5H5 (Cp1)), 4.20 (s, 5H, C5H5 (Cp2)), 4.37 - 4.40 (m, 3H, H7 H10 H11), 4.58 - 4.59 (m,
1H, H9(12)), 4.63 (dd, JHH = 2.3 Hz, 0.6 Hz, 1H, H8), 4.66 - 4.67 (m, 1H, H9(12)), 4.76 (dd, JHH =
2.3 Hz, 0.6 Hz, 1H, H6), 6.93 (s, 1H, H5), 7.01 (td, JHH = 7.6 Hz, 1.2 Hz, 1H, H2), 7.15 (td, JHH =
7.4 Hz, 1.0 Hz, 1H, H3), 7.34 (d, JHH = 7.2 Hz, 1H, H4), 7.89 (d, JHH = 7.8 Hz, 1H, H1) ppm.
13 1 C{ H} NMR (CDCl3): δ = 60.4 (1C, HC6), 60.5 (1C, HC8), 69.1 (1C, HC10(11)), 69.2 (1C,
HC10(11)), 69.6 (5C, (Cp2)), 70.1 (1C, HC9(12)), 70.1 (1C, HC9(12)), 70.4 (1C, HC7), 71.4 (5C,
(Cp1)), 82.8, 88.3, 91.3, 120.2 (1C, HC4), 121.0 (1C, HC5), 124.5 (1C, HC1), 124.6 (1C, HC2),
127.7 (1C, HC3), 135.2, 141.5, 141.8 ppm; UV/Vis: λ (ε) = 395 nm (3630), 485 (3790) nm
–1 (L∙mol ∙cm). IR (KBr) ṽ = 757 (s), 821 (s, δ=C-H double), 1000 (m), 1104 (s, νC-C), 1627 (m),
–1 3093 (w, ν=C-H single) cm . C28H22Fe2 (470.16): calcd. C 71.53, H 4.72; found C 71.62, H 5.43. HRMS (ESI): calcd. for [M]+ 470.0416; found 470.0422.
Complex 9b:
(Cp1)
(Cp2)
° 1 Yield: 50.5 mg (0.107 mmol) 25% based on 8; m.p. 136 C; H NMR (CDCl3): δ = 3.98 (s,
5H, C5H5 (Cp1)), 4.22 (s, 5H, C5H5 (Cp2)), 4.40 (pt, JHH = 2.30 Hz, 2H, H10(11)), 4.46 - 4.47 (m,
1H, H6), 4.68 - 4.69 (m, 2H, H8, H9(12)), 4.96 (dd, 2.3 Hz, 0.4 Hz, 1H, H9(12)), 5.01 (m, 1H, H7),
7.13 (s, 1H, H5), 7.16 - 7.22 (m, 2H, H2-3), 7.36 - 7.40 (m, 1H, H4), 7.58 - 7.60 (m, 1H, H1)
13 1 ppm; C{ H} NMR (CDCl3): δ = 60.9 (1C, HC9(12)), 64.6 (1C, HC9(12)), 68.6 (1C, HC7), 69.4
(5C, (Cp1)), 69.5 (1C, HC6), 69.5 (1C, HC10(11)), 70.1 (1C, HC8), 71.1 (5C, (Cp2)), 71.3 (1C,
HC10(11)), 83.1, 85.1, 91.0, 118.9 (1C, HC5), 119.7 (1C, HC1), 120.2 (1C, HC4), 124.9 (1C,
HC2), 127.3 (1C, HC3), 133.9, 139.0, 144.3 ppm; UV/Vis: λ (ε) = 400 (sh ~3700), 485
–1 (3530), 800 (sh ~65) nm (L∙mol ∙cm); IR (KBr) ṽ = 755 (s), 818 (s, broad, δ=C-H double), 999
-1 (s), 1022 (m), 1105 (s, νC-C), 1241 (m), 1631 (m), 3091 (w, ν=C-H single) cm ; C28H22Fe2
104 (470.16): calcd. C 71.53, H 4.72; found C 71.60, H 5.33; HRMS (ESI): calcd. for [M]+ 470.0416; found 470.0419.
3.5 Synthesis of 3a and 3b from 1,3,5-Triethynylferrocenyl-2,4,6-Triferrocenyl Benzene (4)
3.5.1 Synthesis of 1,3,5-Trichloro-2,4,6-Triethynylferrocenyl Benzene (12)
[CuI] (82.0 mg, 0.430 mmol) and [PdCl2(PPh3)2] (50.0 mg, 70.0 μmol) were dissolved in 50 mL of diisopropylamine and treated with 1.00 g (1.80 mmol) of 1,3,5-trichloro-2,4,6- triiodo-benzene (11), ethynylferrocene (5) (1.50 g, 7.20 mmol) and PPh3 (110.0 mg, 0.430 mmol) and then heated to reflux for 24 h., whereby the reaction solution turned into an orange suspension. After cooling to ambient temperature and evaporation of all volatiles, the orange residue was worked-up by Soxhlet extraction with diethyl ether to remove the ammonium salt formed during the reaction. The orange precipitate was filtered off and washed with cold diethyl ether (2 x 10 mL). The product was dried in vacuum to give an orange solid, soluble in dichloromethane.
Yield: 1.30 g (1.70 mmol, 93 % based on 1,3,5-trichloro-2,4,6-triiodo-benzene); m.p.
1 185 °C (decomp.). H NMR (CDCl3): δ = 4.30 (s, 15 H, C5H5), 4.32 (pt, JHH = 1.90 Hz , 6 H,
13 1 C5H4), 4.61 (pt, JHH = 1.90 Hz, 6 H, C5H4) ppm. C{ H} NMR (CDCl3): δ = 63.9 (FcC≡C), 69.7
(C5H4), 70.4 (C5H5), 72.1 (C5H4), 79.6 (Ci-C5H4), 101.0 (FcC≡C), 123.6 (C6), 136.8 (C-Cl) ppm. IR (KBr) ṽ = 824 (s, δ o.o.p. =C-H), 1025 (m, ν=C-Cl), 1359, 1383 (s, νC-H), 1532 (w, νC=C),
-1 2209 (s, νC≡C), 3088 (w, ν=C-H single) cm . C42H27Fe3Cl3 (805.56): calcd. C 62.62, H 3.38; found: C 62.23, H 3.61. HRMS (ESI): calcd. for [M+] 803.9226; found: 803.9222.
3.5.2 Synthesis of 1,3,5-Triethynylferrocenyl-2,4,6-Triferrocenyl Benzene (4)
Ferrocene (2.70 g, 15.0 mmol) and KOtBu (0.200 g, 1.80 mmol) were dissolved in 60 mL of tetrahydrofuran and the solution was cooled to –80 °C. tButyllithium (1.9 M in n- pentane, 15.2 mL) was added dropwise via a syringe and the solution was stirred for 1 h.
105 Then [ZnCl2·2thf] (10) (4.10 g, 15.0 mmol) was added in a single portion. The reaction
mixture was stirred for additional 30 min at 0 °C. Afterwards, [Pd(CH2C(CH3)2
t P( C4H9)2)(µ-Cl)]2 (0.050 g, 7.0 μmol) and 11 (1.30 g, 1.60 mmol) were added in a single portion and the reaction solution was stirred at 80 °C for 60 h. The crude product was worked-up by column chromatography (column size: 1.5 x 10 cm; alumina). As eluent a n- hexane/diethyl ether mixture of ratio 30:1 (v/v) was used. The 1st fraction contained impure ferrocene, while pure product 4 could be isolated using dichloromethane as eluent. All volatiles were removed under reduced pressure to give the titled compound as an orange solid, soluble in dichloromethane.
1 Yield: 0.230 g (0.18 mmol, 11 % based on 11). m.p. 240 °C (decomp.). H NMR (CDCl3):
δ = 4.19 (s, 15 H, C5H5 (Fc2)), 4.29 (pt, JHH = 1.90 Hz , 6 H, C5H4 (Fc1)), 4.31 (s, 15 H, C5H5
(Fc1)), 4.47 (pt, JHH = 1.90 Hz, 6 H, C5H4 (Fc2)), 4.54 (pt, JHH = 1.90 Hz, 6 H, C5H4 (Fc1)), 5.24
13 1 (pt, JHH = 1.90 Hz, 6 H, C5H4 (Fc2)) ppm. C{ H} NMR (CDCl3): δ = 67.1 (FcC≡C), 67.3 (C5H4,
(Fc2)), 69.0 (C5H4, FcC≡C), 70.1 (C5H5 (Fc2)), 70.2 (C5H5 (Fc1)), 70.7 (C5H4 (Fc1)), 72.8
(C5H4 (Fc2)), 85.1 (Ci-C5H4 (Fc1)), 88.5 (Ci-C5H4 (Fc2)), 100.6 (FcC≡C), 122.5 (FcC≡C-C6),
142.4 (FcC6) ppm. IR (KBr) ṽ = 818 (s, δ o.o.p. =C-H), 1106 (s, νC-C), 1383, 1411 (w, νC-H), 2210
–1 (s, νC≡C), 3094 (w, ν=C-H) cm . C72H54Fe6 (1254.27): calcd. C 68.95, H 4.34; found: C 69.01, H 4.51. HRMS (ESI): calcd. for [M]: 1254.0331; found: 1254.0325.
3.5.3 Synthesis of 3a and 3b from 4
100 mg (0.124 mmol) of 4 were dissolved in m-xylene (40 mL). The orange suspension
was warmed to 60 °C and treated dropwise via syringe with [CpCo(CO)2] (43.0 mg, 0.030 mmol) dissolved in 2.0 mL of m-xylene. The reaction mixture was heated to reflux for 60 h, whereby after 30 min the color changed from orange to deep purple. The solution was
106 cooled to ambient temperature and the solvent was removed. The crude product was worked up by column chromatography (column - size: 3 x 10 cm, alumina) using a n- hexane/diethyl ether mixture of ratio 1:1 (v/v) as eluent. The 1st fraction contained unreacted 4, while the 2nd fraction contained the respective title complex. All volatiles were removed under reduced pressure and a red precipitate could be obtained. Recrystallization from diethyl ether/hexane (ratio 1:1, v/v) afforded purple crystals of 3. Yield: 52.0 mg (0.040 mmol, 52 % based on 4).
4 Supporting information
In this part presented are selected Figures from the Supporting information of this article. Complete Supporting information (Infra-Red Spectra, NMR Spectra, Cyclic Voltammograms, Crystal and Intensity Collection Data) is available on the WWW under http://dx.doi.org/10.1002/ejic.201402659.
4.1 Spectroelectrochemistry of 3a,b
35000
30000
25000 ] -1 20000 cm -1
15000 [L mol [L 10000
5000
0 600 900 1200 1500 1800 2100 2400 2700 3000 Wavelength [nm]
Figure S46: UV/Vis/NIR spectra of 3a in dichloromethane (4.0 mmol∙L-1) at rising potential (-200 mV to ° -1 n 300 mV vs Ag/AgCl) at 25 C, supporting electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4]. Arrows indicate increasing of absorption.
107 35000
30000
25000 ] -1 20000 cm -1
15000 [L mol [L 10000
5000
0 600 900 1200 1500 1800 2100 2400 2700 3000 Wavelength [nm]
Figure S47: UV/Vis/NIR spectra of 3a in dichloromethane (4.0 mmol∙L-1) at rising potential (300 mV to ° -1 n 1000 mV vs Ag/AgCl) at 25 C, supporting electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4]. Arrows indicate decreasing of absorption.
7000
6000
] 5000 -1 cm
-1 4000
3000 mol [L
2000
1000
0 4000 5000 6000 7000 8000 Wavenumber [cm-1]
Figure S48: Deconvolution of the NIR range of the spectrum (1200 nm – 3000 nm) of 3a in dichloromethane (4.0 mmol∙L-1) recorded at the potential of 300 mV (vs Ag/AgCl) at 25 °C, supporting -1 n electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4].
20000
18000
16000
] 14000 -1
cm 12000 -1 10000
mol [L 8000
6000
4000
2000
0 500 1000 1500 2000 2500 3000 Wavelength [nm]
Figure S49: UV/Vis/NIR spectra of 3b in dichloromethane (3.3 mmol∙L-1) at rising potential (-200 mV to ° -1 n 500 mV vs Ag/AgCl) at 25 C, supporting electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4]. Arrows indicate increasing of absorption.
108 20000
18000
16000
14000 ] -1 12000 cm -1 10000
8000 [L mol [L 6000
4000
2000
0 500 1000 1500 2000 2500 3000 Wavelength [nm]
Figure S50: UV/Vis/NIR spectra of 3b in dichloromethane (3.3 mmol∙L-1) at rising potential (500 mV to ° -1 n 1300 mV vs Ag/AgCl) at 25 C, supporting electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4]. Arrows indicate decreasing of absorption.
3000
2500
2000 ] -1
cm 1500 -1
1000 [L mol [L
500
0 4000 5000 6000 7000 8000 Wavenumber [cm-1]
Figure S51: Deconvolution of the NIR range of the spectrum (1200 nm – 3000 nm) of 3b in dichloromethane (3.3 mmol∙L-1) recorded at the potential of 500 mV (vs Ag/AgCl) at 25 °C, supporting -1 n electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4].
4.2 Conversion of Isomer 9a to 9b – Electrochemical and Chemical oxidation
16000
14000
12000 ]
-1 10000 cm -1 8000
[L mol [L 6000
4000 9a 2000 9b
0 500 1000 1500 2000 2500 3000 Wavelength [nm]
Figure S58: UV/Vis/NIR spectra of 9a and 9b before applying potential.
109 16000
14000
12000 ]
-1 10000 cm -1 8000
[L mol [L 6000 9a+ 4000 9b+ 2000
0 500 1000 1500 2000 2500 3000 WavelengthWavelength [nm]
Figure S59: UV/Vis/NIR spectra of 9a+ and 9b+ after one electron oxidation.
18000
16000
14000 ]
-1 12000 cm
-1 10000
8000 [Lmol 6000
4000 9a2+ 2+ 2000 9b
0 500 1000 1500 2000 2500 3000 Wavelength [nm]
Figure S60: UV/Vis/NIR spectra of 9a2+ and 9b2+ after two electron oxidation.
16000
14000
12000 ]
-1 10000 cm -1 8000
[L mol [L 6000
4000 9a after reduction 2000 9b after reduction
0 500 1000 1500 2000 2500 3000 Wavelength [nm]
Figure S61: UV/Vis/NIR spectra of 9a and 9b after reduction.
4.3 Chemical oxidation experiment
3.10 mg (0.007 mmol) of Isomer 9a was dissolved in the NMR tube in about 0.4 mL of
1 D6-benzene. A H NMR spectrum was recorded (Figure S62, A). About 3.30 mg (0.014
mmol, 2 eq) of [AgPF6] was dissolved in 0.4 mL of D6-benzene and the solution was added to the NMR tube with the solution of 9a, whereby Ag precipitated. Filtration through a small piece of filter paper placed in a glass pipette, to another NMR tube was than undertaken. 1H NMR spectrum was recorded (Figure S62, B). The same experiment was repeated with isomer 9b (Figure S62, C and D).
110
(D)
(C)
(B)
(A)
Figure S62: Chemical oxidation experiment - 1H NMR spectra: (A) isomer E (9a) before reaction with [AgPF6], (B) isomer E (9a) after reaction with [AgPF6], (C) isomer Z (9b) before reaction with [AgPF6], (D) isomer Z (9b) after reaction with [AgPF6].
5 References
[D1] a) A. K. Diallo, J.-C. Daran, F. Varret, J. Ruiz, D. Astruc, Angew. Chem. Int. Ed. 2009, 48, 3141–3145–3191; Angew. Chem. 2009, 121, 3187–3191; b) A. K. Diallo, C. Absalon, J. Ruiz, D. Astruc, J. Am. Chem. Soc. 2011, 133, 629–641.
[D2] Y. Yu, A. D. Bond, P. W. Leonard, U. J. Lorenz, T. V. Timofeeva, K. P. C. Vollhardt, G. D. Whitener, A. A. Yakovenko, Chem. Commun. 2006, 2572–2574.
[D3] a) Y. Yu, A. D. Bond, P. W. Leonard, K. P. C. Vollhardt, G. D. Whitener, Angew. Chem. Int. Ed. 2006, 45, 1794–1799; Angew. Chem. 2006, 118, 1826–1831; b) G. A. Mirafzal, N. L. Bauld, Organometallics 1991, 10, 2506–2508.
[D4] a) M. J. Eichberg, B. Kayser, P. W. Leonard, O. Š. Miljanić, T. V. Timofeeva, K. P. C. Vollhardt, G. D. Whitener, A. Yokovenko, Y. Yu, Inorg. Chim. Acta 2011, 369, 32–39; b) M. D. Rausch, F. A. Higbie, G. F. Westover, A. Clearfield, R. Gopal, J. M. Troup, I. Bernal, J. Org. Chem. 1978, 149, 245–264; c) J. Kotz, G. Neyhart, W. Vinning, M. D. Rausch, Organometallics 1983, 2, 79–82; d) J. Jiao, G. J. Long, F. Grandjean, A. M. Beatty, T. P. Fehlner, J. Am. Chem. Soc. 2003, 125, 7522–7523; e) J. Jiao, G. J. Long, F. Grandjean, A. M. Beatty, T. P. Fehlner, J. Am. Chem. Soc. 2005, 127, 17819–17831.
[D5] a) A. Hildebrandt, T. Rüffer, E. Erasmus, J. C. Swarts, H. Lang, Organometallics 2010, 29, 4900–4905; b) A. Hildebrandt, D. Schaarschmidt, R. Claus, H. Lang, Inorg. Chem. 2011, 50, 10623–10632; c) A. Hildebrandt, D. Schaarschmidt, H. Lang, Organometallics 2011, 30, 556–563; d) J. M. Speck, D. Schaarschmidt, H. Lang,
111 Organometallics 2012, 31, 6373–6380; e) K. Kaleta, F. Strehler, A. Hildebrandt, T. Beweries, P. Arndt, T. Rüffer, A. Spannenberg, H. Lang, U. Rosenthal, Chem. Eur. J. 2012, 18, 12672–12680; f) A. Hildebrandt, H. Lang, Organometallics 2013, 32, 5640– 5653. [D6] M. D. Rausch, R. A. Genetti, J. Org. Chem. 1970, 35, 3888–3897.
[D7] N. Miyaura, A. Suzuki, Org. Synth. 1990, 68, 130–132.
[D8] a) E. I. Negishi, A. O. King, N. Okukado, J. Org. Chem. 1977, 42, 1821; b) A. Hildebrandt, D. Schaarschmidt, L. van As, J. C. Swarts, H. Lang, Inorg. Chim. Acta 2011, 374, 112– 118; c) U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Rüffer, P. J. Low, H. Lang, Organometallics 2013, 32, 6106–6117.
[D9] FcZnCl was prepared in situ by monolithiation of ferrocene according to a procedure [D10] reported by Müller-Westerhoff and consecutive zincation with [ZnCl2·2thf] (10) (see the Supporting Information).
[D10] R. Sanders, U. T. Müller-Westerhoff, J. Organomet. Chem. 1996, 512, 219–224.
[D11] H. C. Clark, A. B. Goel, Inorg. Chim. Acta 1978, 31, L441–L442.
[D12] a) P.-S. Lee, T. Fujita, N. Yoshikai, J. Am. Chem. Soc. 2011, 133, 17283–17295; b) T. Yamakawa, N. Yoshikai, Org. Lett. 2013, 15, 196–199.
[D13] Y. J. Chen, D.-S. Pan, C.-F. Chiu, J.-X. Su, S. J. Lin, K. S. Kwan, Inorg. Chem. 2000, 39, 953–958.
[D14] A.-C. Ribou, J.-P. Launay, M. L. Sachtleben, H. Li, C. W. Spangler, Inorg. Chem. 1996, 35, 3735–3740.
[D15] R. J. LeSuer, C. Buttolph, W. E. Geiger, Anal. Chem. 2004, 76, 6395–6401.
[D16] D. Schaarschmidt, A. Hildebrandt, H. Lang, J. Organomet. Chem. 2014, 752, 133–140.
[D17] U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Hahn, S. Liebing, J. Kortus, H. Lang, Organometallics 2012, 31, 6761–6771.
[D18] a) N. S. Hush, Prog. Inorg. Chem. 1967, 8, 391–444; b) N. S. Hush, Electrochim. Acta 1968, 13, 1005.
[D19] D. M. D’Alessandro, F. R. Keene, Chem. Soc. Rev. 2006, 35, 424–440.
[D20] M. Robin, P. Day, Adv. Inorg. Chem. Radiochem. 1967, 10, 1967.
[S21] M. Rosenblum, N. Brawn, J. Papenmeier, M. Applebaum, J. Organometal. Chem. 1966, 6, 173 - 180.
[S22] J. Polin, H. Schottenberger, Org. Synth. 1996, 73, 262 – 267.
[S23] U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Rüffer, P. J. Low, H. Lang, Organometallics 2013, 32, 6106-6117.
[S24] C. M. Reddy, M. T. Kirchner, R. C. Gundakaram, K. A. Padmanabhan, G. R. Desiraju, Chem. Eur. J. 2006, 12, 2222 – 34.
112 [S25] R. J. LeSuer, C. Buttolph, W. E. Geiger, Anal. Chem. 2004, 76, 6395 – 401.
[S26] N. Miyaura, A. Suzuki, Org. Synth. 1990, 68, 130 – 132.
[S27] H. C. Clark, A. B. Goel, Inorg. Chim. Acta 1978, 31, 441 – 442.
113 CHAPTER E Coordination Behavior of (Ferrocenylethynyl)diphenyl- phosphane Towards Binuclear Iron and Cobalt Carbonyls
G. Filipczyk, A. Hildebrandt, T. Rüffer, M. Korb, H. Lang, J. Organomet. Chem., 2017, 142– 151.
All the described products were synthesized and characterized by the author. The crystal X-ray structure data were collected, processed by Tobias Rüffer and Marcus Korb. The discussion of the structures was accomplished by the author in cooperation with Tobias Rüffer. The (spectro)electrochemical experiments were conducted by the author. The results were consulted with Alexander Hildebrandt.
1 Introduction
The reaction chemistry of phosphinoacetylides of the general formula PR′3-n(C≡CR)n (R = R′, R ≠ R′; R, R′ = single-bonded organic group; n = 1, 2, 3) towards different metal carbonyls was the subject to numerous experimental and theoretical studies for many
decades, due to their versatility as multifunctional ligands. In addition, P–C(sp) bond cleavage enables an interesting follow-up chemistry.[E1–9] The rich chemistry of this class of compound results from the ability to bind to metal centers either by the phosphorus atom, by the acetylic unit or by both. Additionally, different binding modes are possible,
2 2 2 such as μ-symmetrical, μ,η -edge-bridging and μ3-η - or μ4-η -face-bridging, whereby the phosphinoacetylides act either as two- or four-electron donor ligands.[E10,11] Examples of this family of organometallic compounds are mono- or dinuclear complexes of the general
[E8] [E9,12] formula M(CO)3(P(C≡CPh)3)3, M(CO)6-n(PPh2(C≡CPh))n (M = Cr, Mo, W; n = 1, 2),
2 [E5] 2 PR2((η -C≡CPh)Co2(CO)6) and M2(CO)6(μ,η -C≡CR)(µ-PPh2) (M = Fe, Ru, Os; R = single- bonded organic ligand).[E1,2,4] In addition, cyclic compounds such as
[E6] 2 Fe2(CO)6(PPh2(C≡CR))2 and Ni2(CO)2(PPh2(C≡CR))2 exist. {(R′C≡C)2P((η -C≡CR)
Co2(CO)5)}2 (R = R′; R ≠ R′) is a species containing a six-membered C2Co2P2 ring, which is
[E3,5] available by the reaction of P(C≡CR)3 with Co2(CO)8. Annular heterometallic star-
shaped compounds of type 1,3,5-(Ph2PC≡C)3C6H3, 1,3,5-((MLn)Ph2PC≡C)3C6H3 (MLn =
M(CO)5, M = Mo, W; MLn = Os3(CO)11) and 1,3,5-(M(CO)5(Ph2P((η2-C≡C)Co2(CO)6)3C6H3) (M = Mo, W) have also been reported.[E7]
114 (Ferrocenylethynyl)diphenylphosphane shows, due to its redox-active ferrocenyl unit, not only an interesting coordination behavior towards different early and late transition metals, but also promising electronic properties[E13–20] as characteristic, for example, for
6 i [E14] [((FcC≡C)Ph2P)(RuCl2(η -p-cymene)] (p-cymene = 1- C3H7-4-CH3-C6H4), [trans-
[E15] RuCl2(PPh2(C≡CFc))4], cis/trans-[Ru(C≡CR)2(PPh2(C≡CFc))4] (R = Ph, Tol), cis/trans-
[E17,19] [E19] [PdX2(PPh2(C≡CFc))2] (X = Cl, I), [Pd(Cl)(μ-Cl)(PPh2(C≡CFc))]2, cis-[PtCl2(PPh2
[E17] [E16,20] [E20] (C≡CFc))2], cis/trans-[Pt(C≡CFc)2(PPh2(C≡CFc))2], [AuCl(PPh2(C≡CFc))],
5 5 [Au(C≡CFc)(PPh2(C≡CFc))], and [Au(C≡CRc)(PPh2(C≡CFc))] (Rc = Ru(η -C5H4)(η -
[E20] C5H5)). Some of these compounds were used as catalysts in homogeneous catalysis,[E14,19] while the respective platinum and gold species show anticancer activities.[E21]
In this article we enrich the complexation behavior of PPh2(C≡CFc) towards the binary carbonyl compounds Fe2(CO)9 and Co2(CO)8. The electrochemical properties of the newly prepared metal carbonyl compounds and the structures of four species in the solid-state are reported.
2 Results and Discussion
(Ferrocenylethynyl)diphenylphosphane (1) was prepared by the reaction of FcC≡CH
n [E17– with BuLi followed by the consecutive addition of Ph2PCl according to references 19,22].
If phosphane 1 was reacted with Fe2(CO)9 (2) in a 1:1 molar ratio in tetrahydrofuran at
5 5 50 °C the iron tetra-carbonyl compound Fe(CO)4(PPh2(C≡CFc)) (4) (Fc = Fe(η -C5H4)(η -
C5H5)) was formed, which after appropriate workup could be isolated in a yield of 84 %
(Experimental Part) (Scheme E1). In addition to 4, Fe(CO)3(PPh2(C≡CFc))2 (5) (5 % yield)
2 and Fe2(CO)6(µ,η -C≡CFc)(µ-PPh2) (6) (4 % yield) could be isolated (Experimental Part). A further possibility to synthesize 6 is given by treatment of 4 with 2 in boiling toluene
(Scheme E1), confirming that 6 is formed via 4. In 4 and 5 the PPh2(C≡CFc) phosphorus atom is datively bonded to the 16- or 14-valence electron fragment Fe(CO)4 or (Fe(CO)3, while in 6 the PPh2 unit is µ-bridging a dinuclear Fe2(CO)6 organometallic building block
115 indicating that a phosphorus-carbon bond cleavage in PPh2(C≡CFc) occurred during the reaction. A mechanism for the formation of 6 is published elsewhere.[E1,2,10]
Scheme E1. Synthesis of 4 – 6 from 1 and 2.
Since 1 and 4 feature a non-coordinated alkynyl (1, 4) and/or phosphane (1) unit, these
compounds were reacted with binary Co2(CO)8 (3) in toluene–hexane mixtures of ratio
2 1:1 (v/v) (Scheme E2). After appropriate work-up, compounds PPh2((η -C≡CFc)Co2(CO)6)
2 (7) and Co2(CO)7(PPh2((η -C≡CFc)Co2(CO)6)) (8) could be isolated as green (7) or dark brown (8) solids in yields of 24 % (7) and 46 % (8), respectively (Experimental Part). In 7
the alkynyl unit is π-bonded to a Co2(CO)6 fragment, resulting in the formation of a dicobalta tetrahedrane moiety.[E23–30] In 8 the phosphorus atom is additionally
coordinated to a Co2(CO)7 unit (Scheme E2).
Organometallic compound 7 decomposes in air and moisture both in solution and in the solid state, while 8 is fairly stable in the solid state. Phosphanes similar to 8 of the
n [E31] form Co2(CO)7(PR3) (R = C4H9, C6H11, C6H5) are known. They were found to possess
[E31] limited stability and decompose to give Co2(CO)8 and [Co(CO)3(PR3)]2. It is anticipated
2 that 7 shows a similar reaction behavior as recently reported for {P(C≡CR′)2((η -
C≡CR)Co2(CO)5)}2 (R = R′; R ≠ R′; R, R′ = single-bonded organic ligand) in which a six-
[E3,5] membered C2Co2P2 ring as constitutional component is present (vide supra). However, we were not able to isolate such a species. Nevertheless, when 7 was further
reacted with one equivalent of Fe2(CO)9 (2) in tetrahydrofuran, compound
116 2 Fe(CO)4(PPh2((η -C≡CFc)Co2(CO)6)) (9) could be isolated as a dark solid (Scheme E2, Experimental Part). This compound was also accessible, when 4 was reacted with one equiv of Co2(CO)8 (3) (Scheme E2, Experimental Part). Compound 9 is isostructural to, for
2 example, Fe(CO)4(PPh2((η -C≡CPh)Co2(CO)6)), which was synthesized by Mays and coworkers.[E32] Compound 9 is, in contrast to 7 and 8, stable under ambient conditions.
Scheme E2. Synthesis of 7 – 9.
The identification of 4 – 9 is based on IR and NMR (1H, 13C{1H}, 31P{1H}) spectroscopy, including 2-D NMR experiments and high-resolution ESI-TOF mass spectrometry (Experimental Part). Elemental analysis confirms the composition of the respective organometallic compounds (Experimental Part). Additionally, the molecular structures of 4 and 6 – 8 in the solid state were determined by single crystal X-ray diffraction analysis.
The 1H NMR spectra of 4 – 9 are characterized by the phenyl signals between 7.4 – 8.1 ppm, the singlet for the C5H5 protons and the pseudo-triplets for the C5H4 hydrogen atoms with JHH = 1.9 Hz for the Fc units (Experimental Part, Electronic Supplementary Material). Equally informative are the respective 13C{1H} NMR spectra (for HMQC NMR experiments see Electronic Supplementary Material). The resonance signal of the carbonyl groups of 4
2 appears as a doublet at 213.1 ppm ( JPC = 19.4 Hz), while the one of 5 is observed as a
2 triplet at 214.0 ppm ( JPC = 29.8 Hz), confirming exchange processes between the axial and equatorial CO groups.[E33,34] For 6 a CO signal at 210.4 ppm is characteristic, pointing to dynamic interchange processes (supported by HMQC NMR experiments (Electronic Supplementary Material)), as also recently reported for similar compounds by Cherkas et
117 al.[E2] The alkynyl carbon atoms in 4 and 5 resonate at 81.5 and 113.2 ppm (4) and at 70.9
and 111.6 ppm (5), while for 6 two signals were recorded as doublets at 93.2 (JPC = 7.3 Hz)
and 103.0 ppm (JPC = 52.4 Hz) (Experimental Part, Electronic Supplementary Material). The 13C{1H} NMR spectrum of 9 shows a doublet at 213.7 ppm with a coupling constant of
2 2 JPC = 17.3 Hz (Fe(CO)4 unit; for comparison 4, 213.1 ppm, JPC = 19.4 Hz) and a broad
[E32,35] signal at 198.8 ppm for the Co2(CO)6 moiety.
31P{1H} NMR spectroscopy allows to monitor the reaction progress of 1 with 2 to give 4 – 6 as well as 1 and 4 with 3 to produce 7 – 9 (Experimental Part). Organometallic 1 shows its phosphorus signal at –32.8 ppm,[E17–19] while the signals of 4 – 9 are shifted to lower field and are observed at 48.8 (4), 58.8 (5), 147.7 (6), 0.3 (7), 21.9 (8) and 76.1 ppm (9), respectively (Experimental Part). This shifting is characteristic for the coordination of phosphanes to transition metal fragments.[E17–19,32]
The most characteristic feature in the IR spectra of 4 and 5 is the appearance of the absorption of the C≡C triple bond at 2159 cm-1 for 4 and at 2156 cm–1 for 5. In 6, where
2 the C≡CFc unit is µ,η -bonded to a Fe2(CO)6 building block the ν(C≡C) band could not
[E1,2,4,10,36] unequivocally be assigned. In addition, strong ν(CO) bands were observed at 2045, 1972, 1945 and 1925 cm–1 for 4 and at 1973 and 1881 cm–1 for 5, as typical for
[E37–42] Fe(CO)4 and Fe(CO)3 metal carbonyl fragments. The ν(CO) stretching vibrations of 5 are in accordance with a symmetrical coordination of both phosphino-acetylides in a
axial-trans position (D3h), similarly as in, i. e. trans-Fe(CO)3(PPh3)2 (ν(CO) 1950 (vw), 1894
–1 [E39,43] (vs) cm ). In contrary to 5, in Fe(CO)3(PPh2(C≡CPh)2, the strong ν(CO) vibration
–1 [E41] splits into two bands (1901, 1889 cm ; in CHCl3). For the Fe2(CO)6 unit in 6 four ν(CO) vibrations were found at 2067, 2029, 1994 and 1961 cm–1 (Experimental Part), which is
2 [E1,2] typical for this family of compounds, i. e. [Fe2(CO)6(µ,η -C≡CPh)(µ-PPh2)]. For 7 a total of five CO stretching vibrations between 2086 – 1957 cm–1 are typical, while for 8 eleven CO bands were observed in the range of 2065 to 1850 cm–1 (Experimental Part).
–1 For 9 the ν(CO) absorptions appear between 2090 and 1870 cm with a pattern typical for
2 [E32] this type of compounds, i. e. Fe(CO)4(PPh2((η -C≡CPh)Co2(CO)6)).
The structures of 4 and 6 – 8 in the solid-state were determined by single crystal X-ray structure analysis. Figure E1 shows the molecular structure of 4, the one of 6 is depicted in Figure E2, while the result of the structure analyses of 7 and 8 are presented in Figures E3 and E4. Selected bond distances (Å), bond angles (°) and torsion angles (°) are
118 summarized in the captions of Figures E1 – E4. For crystal and structure refinement data see Experimental Part and Table S1 (Electronic Supplementary Material).
Figure E1. ORTEP diagram (50 % probability level) of the molecular structure of 4. Hydrogen atoms and the dichloromethane molecule have been omitted for clarity. Selected bond distances (Å) and angles (°): P1–C17 1.757(3), C17–C18 1.194(4), C18–C19 1.425(4), P1–C5 1.827(3), P1–C11 1.825(3), P1–Fe1 2.2286(7), Fe1– C1 1.803(3), Fe1–C2 1.809(3), Fe1–C3 1.790(3), Fe1–C4 1.791(3), Fe2–D1 1.646(1), Fe2–D2 1.651(1); P1– C17–C18 173.2(2), C17–C18–C19 177.8(3), C17–P1–C11 103.11(13), C17–P1–Fe1 113.15(9), C11–P1–Fe1 114.48(8), C5–P1–Fe1 117.85(9), P1–Fe1–C3 177.55(10), C1–Fe1–C2 114.08(14), C1–Fe1–C4 126.63(15), C2–Fe1–C3 93.55(13), D1–Fe2–D2 178.4. (D1/D2 denotes the geometrical centroids of C19–C23/C24–C28).
Figure E2. ORTEP diagram (50 % probability level) of the molecular structure of 6. Hydrogen atoms have been omitted for clarity. Selected bond distances (Å) and angles (°): Fe1–Fe2 2.5772(16), Fe1–P1 2.208(2), Fe2–P1 2.216(2), Fe1–C1 1.893(8), Fe2–C1 2.129(8), Fe2–C2 2.345(8), C1–C2 1.254(11), C2–C3 1.418(11), Fe1–C25 1.785(8), Fe1–C26 1.801(9), Fe1–C27 1.800(8), Fe2–C28 1.793(10), Fe2–C29 1.774(8), Fe2–C30 1.770(9), Fe3–D1 1.648(4), Fe3–D2 1.656(4); Fe1–P1–Fe2 71.26(8), P1–Fe1–C1 77.5(2), Fe1–C1–C2 161.7(7), C1–C2–C3 169.3(9), P1–Fe1–Fe2 54.52(6), Fe2–Fe1–C1 54.3(2), Fe2–C1–C2 83.5(5), Fe2–C2–C1 64.4(5), Fe2–C2–C3 126.3(6), P1–Fe2–C1 72.8(2), P1–Fe2–C2 88.6(2), D1–Fe3–D2 179.7 (D1/D2 denotes the geometrical centroids of C3–C7/C8–C12).
119
Figure E3. ORTEP diagram (50 % probability level) of the molecular structure of 7. Hydrogen atoms have been omitted for clarity. Selected bond distances (Å) and angles (°): Co1–Co2 2.4713(5), Co1–C1 1.967(3), Co1–C2 1.985(3), Co2–C1 1.983(3), Co2–C2 1.966(3), P1–C1 1.793(3), C2–C3 1.448(4), Fe1–D1 1.651(1), Fe1–D2 1.652(1); P1–C1–C2 141.6(2), C1–C2–C3 143.3(3), Co1–Co2–C1 50.98(7), Co1–Co2–C2 51.62(7), Co1–C1–C2 70.74(15), C1–C2–Co1 69.34(15), C1–C2–Co2 70.74(15), P1–C1–Co1 123.50(14), P1–C1–Co2 144.05(14), D1–Fe1–D2 177.6 (D1/D2 denotes the geometrical centroids of C3–C7/C8–C12).
Figure E4. ORTEP diagram (50 % probability level) of the molecular structure of 8. Hydrogen atoms and the nhexane molecule as packing solvent have been omitted for clarity. Selected bond distances (Å) and angles (°): Co1–Co2 2.4566(9), Co1–C1 2.003(4), Co1–C2 1.970(4), Co2–C1 1.953(4), Co2–C2 1.986(4), P1–C1 1.789(4), C2–C3 1.436(6), P1–Co3 2.1887(12), Co3–Co4 2.6725(9), Co4–C36 1.788(5) Fe1–D1 1.646(2), Fe1–D2 1.660(2); P1–C1–C2 140.7(3), C1–C2–C3 141.4(4), Co1–Co2–C1 52.54(12), Co1–Co2–C2 51.31(12), Co1–C1–C2 68.8(2), C1–C2–Co1 71.5(2), C1–C2–Co2 68.6(2), P1–C1–Co1 136.5(2), P1–C1–Co2 134.1(2), P1–Co3–Co4 177.91(4), Co3–Co4–C36 174.74(15), D1–Fe1–D2 175.7 (D1/D2 denotes the geometrical centroids of C3–C7/C8–C12).
120
The compounds crystallize in the triclinic space group P–1 (6 and 8) or in the monoclinic space group P21/n (4 and 7) and exhibit C1 point symmetry in the solid state.
Common features of 4, 7 and 8 (Figures E1, E3, E4) is that the PPh2(C≡CFc) building block coordinates in a κP fashion to a Fe(CO)4 fragment (4), in a µ-κC: κC′ manner to a Co2(CO)6 unit (7, 8) and additionally for 8 in a κP mode to Co2(CO)7.
In 4, the bond lengths and angles of the PPh2(C≡CFc) ligand show some differences,
[E18] when compared to 1. The P–CPh and the C≡C bonds in 4 are slightly shorter than in 1
[E18] (P–CPh: 1.825(3) – 1.827(3) vs 1.833 – 1.848 Å ; C≡C: 1.194(4) vs 1.210(10) and 1.203(11)[E18] Å). The P1–C17–C18 angle is somewhat larger as compared to 1 (173.2(2)
[E18] [E18] vs 169.2(7) Å ). However, the P–C(sp) bond lengths for 1 and 4 are almost identical.
The Fe1 atom of the κP-coordinated Fe(CO)4 unit forms a FeC4P coordination setup, which exhibits a trigonal-bipyramidal coordination geometry as expressed by its τ parameter of 0.975.[E44] The phosphorus atom occupies one of the axial positions and the P–Fe bond length of 4 (2.2286(7) Å) is slightly shorter in comparison to, for example,
[E45] Fe(CO)4(PPh3) (2.244(1) Å), Fe(CO)4(L-κP) (where L = 1-(diphenylphosphanyl)-1’-
[E46] 2 [E32] vinylferrocene) (2.237(1) Å), or Fe(CO)4(PPh2((η -C≡CPh)Co2(CO)6)) (2.259(1) Å), but comparable to the bond lengths reported for (Fe(CO)4)2(μ-bdpp) (2.215(2), 2.221(1)
[E47] Å) (bdpp = Ph2PC≡CC≡CPPh2). Due to steric reason, the “PC3” unit around the diphenyl(ethynyl)-substituted P1 atom of 4 is observed in a nearly ideal staggered conformation with respect to the Fe(CO)4 fragment as revealed, for example, by the C17– P1–Fe1–C1 torsion angle of 59.1(2) °.
Organometallic compounds 7 and 8 contain a C2Co2 dicobalta-tetrahedrane unit (Figures E3 and E4). The bond lengths and angles of this building block reveal a pseudo- tetrahedral geometry of this fragment, where the respective Co1–C1, Co1–C2, Co2–C1 and Co2–C2 bonds differ somewhat in length and the corresponding angels are dissimilar (Figures E3 and E4). The same structural motif was recently reported in related
2 [E32] 2 5 Fe(CO)4(PPh2((η -C≡CPh)Co2(CO)6)) and (Fp)PPh2((η -C≡CPh)Co2(CO)6) (Fp = Fe(η -
[E35] C5H5)(CO)2). The Co–Co bond lengths of 2.4713(5) and 2.4566(9) (Å) of 7 and 8 are comparable and are in accordance to literature known similar species.[E32,35] Compound 8 holds also a Co2(CO)7 fragment coordinated by the phosphorus atom. In comparison to the two known structures of Co2(CO)8 (an unbridged isomer and one, where the cobalt atoms are bridged by two CO groups[E48,49]), replacement of a CO ligand by a datively-bonded
121 phosphorus atom induces elongation of the Co–Co bond (2.52[E48] vs 2.67 (Å)) with respect
[E49] to the major bridged structure of Co2(CO)8 or shortening (2.70 vs 2.67 (Å)) with respect to the minor unbridged structure, confirming the coordination of the phosphane to the cobalt-carbonyl moiety.
The length of the P–Co bond in 8 is 2.1887(12) (Å) and is slightly shorter as in related
Co2(CO)7(PPh3) (2.1976(10)), similarly the Co–Co bond of the Co2(CO)7 functionality
[E50] (2.6725(9) vs 2.6869(7)). The equatorial CO ligands in the Co2(CO)7 moiety adopt a
[E50] staggered conformation (Figure 4) in the same way as in Co2(CO)7(PPh3). The Co–Co– CO axis deviates slightly from linearity, with the angel at the central Co being 174.74(15) °
[E50] and is even slightly smaller as in Co2(CO)7(PPh3) (178.45).
Compound 6 (Figure E2) differs from the above described organometallic carbonyl compounds in the way that the molecule possesses a diphenylphosphido unit bridging the
Fe2(CO)6 (Fe–Fe) moiety, which confirms a cleavage of the P–C(sp) bond in 1 and 4, respectively, during the course of the reaction (Experimental Part).[E1,10] The Fe1–Fe2 distance is with 2.5772(16) Å comparable to structural analogous compounds, i. e.
2 [E4] 2 Fe2(CO)6(μ,η -C≡CPh)(μ-PPh2) (2.597(2) Å) . The same holds true for the Fe2(CO)6(µ,η -
[E2] C≡CFc) building block. The Fe1–C1 bond (1.893(8) Å) corresponds to a Fe–C(sp) bond , while Fe2–C1 and Fe2–C2 is of π character (2.129(8) and 2.345(8) Å) (Figure E2). These
2 bond lengths agree with those ones found in Fe2(CO)6(μ,η -C≡CPh)(μ-PPh2) (1.891(6), 2.125(8) and 2.304(7) Å).[E4] In the same way, as in the mentioned compound, the dual bonding of the acetylide unit causes deviation of the Fe1–C1–C2 and C1–C2–C3 angles from linearity (161.7(7) and 169.3(9) °).
The redox behavior of 4 – 6 and 9 was investigated by cyclic voltammetry and square-
−1 n wave voltammetry in a 0.1 mol∙L solution of [ Bu4N][B(C6F5)4] in dichloromethane as supporting electrolyte[E51–67] (Experimental Part). The appropriate voltammograms are shown in Figures E5 − E8, while the respective data are summarized in Table E1 and are referenced against the FcH/FcH+ redox couple (E°′ = 0 V) as recommend by IUPAC[E68] (Experimental Part).
The cyclic voltammogram of 4 in the potential range of −1000 to +1500 mV shows an
irreversible oxidation of the iron carbonyl functionality at Epa = 270 mV with the
corresponding reduction of the thus formed species at Epc = −670 mV and one presumably
reversible redox event of the Fc unit at E°′ = 470 mV, however, with a relatively high ΔEp
122 value of 120 mV (Figure E5). Measurements in the potential range between −100 and 1000 mV showed that the occurrence of the oxidation process at 270 mV is directly coupled to the reduction at −670 mV. Without the re-reduction of the Fe(CO)4 unit only the reversible Fc redox process was detected (dashed line, Figure E5). Multicyclic electrochemical experiments demonstrated the stability of the follow-up products of the electrochemically irreversible oxidation at Fe(CO)4 (Electronic Supplementary Material, Figure S32a-d).
-1500 -1000 -500 0 500 1000 1500 Potential [mV] vs FcH/FcH+
Figure E5. Cyclic voltammograms of 4 measured in the potential range from −1000 to 1400 mV (solid line) and −100 to 1000 mV (dashed line) (vs FcH/FcH+, E°′ = 0 mV) in dichloromethane (1.0 mmol∙L−1). −1 n Measurement conditions: 25 °C, scan rate 100 mV/s, supporting electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4], working electrode glassy-carbon.
Coordination of the alkyne unit to a Co2(CO)6 fragment as characteristic in 9 led to a reverse of the order of the electrochemical events and hence the ferrocenyl unit is oxidized at a lower potential than the iron carbonyl moiety. A reversible Fc/Fc+ redox couple is observed at E°′ = 145 mV (ΔEp = 83 mV) followed by an oxidation process at Epa
= 490 mV with a corresponding reduction at Epc = 320 mV (Figure E6). The shape of the 2nd oxidation wave suggests an irreversible 3rd oxidation at approximately 700 mV. However, this 3rd oxidation process disappears, when the measurement is conducted between −500 mV and 1500 mV, therefore it seems plausible that the corresponding reduction is the process found at Epc = −1000 mV (Figure E6).
In contrast to the cyclic voltamogramm of 4, for compound 5 (Figure E7) an electrochemical reversible oxidation of the Fe(CO)3 unit at E°′ = 150 mV was found (Figure E7). In addition, a second oxidation is observed at 280 mV which can be assigned to a simultaneous oxidation of both Fc units and hence shows the double peak current.
Another irreversible oxidation of 5 is observed at Epa = 1220 mV most likely due to a
123 second oxidation at the Fe(CO)3 functionality accompanied with the decomposition of the compound (Figure E7).[E64,69,70] The redox potential related to the Fc/Fc+ couple in 5 is less anodic than in uncoordinated 1.[E19]
-1500 -1000 -500 0 500 1000 1500 Potential [mV] vs FcH/FcH+
Figure E6. Cyclic voltammograms of 9 measured in the potential range from −1250 to 1250 mV, (solid line), from −500 to 1500 mV (dotted line) and from −200 to 400 mV (dashed line) (vs FcH/FcH+, E°′ = 0 mV) in dichloromethane (1.0 mmol∙L−1). Measurement conditions: 25 °C, scan rate 100 mV/s, supporting −1 n electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4], working electrode glassy-carbon.
-800 -400 0 400 800 1200 1600 Potential [mV] vs FcH/FcH+
Figure E7. Top: Cyclic voltammograms of 5 measured in the potential range −100 to 600 mV (dashed line) and −600 to 1600 mV (solid line). Bottom: Square-wave voltammogram (vs FcH/FcH+, E°′ = 0 mV) in dichloromethane (1.0 mmol∙L−1). Measurement conditions: 25 °C, 100 mV/s scan rate, supporting −1 n electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4], glassy-carbon working electrode.
Compound 6 shows one electrochemically reversible redox process at E°′ = 90 mV (∆Ep = 70 mV), which can be attributed to the ferrocenyl/ferrocenium redox couple. In
addition, two irreversible processes related to the iron carbonyl units at Epa = 980 and 1430 mV are observed (Figure E8).[E64,69,70]
124 -200 0 200 400 600 800 1000 1200 1400 1600 Potential [mV] vs FcH/FcH+
Figure E8. Cyclic voltammogram of 6 in the potential range of −200 to 1600 mV (vs FcH/FcH+, E°′ = 0 mV) in dichloromethane (1.0 mmol∙L−1). Measurement conditions: 25 °C, 100 mV/s scan rate, supporting −1 n electrolyte 0.1 mol∙L [ Bu4N][B(C6F5)4], glassy-carbon working electrode.
Phosphanes coordinated to iron-carbonyl moieties of the general form Fe(CO)5-n(PPh3)n (n = 1, 2) were electrochemically investigated and show strong dependence on the material of the working electrode, the solvent used and demonstrate irreversibility and decomposition of the oxidized species.[E71–73] The shape of the cyclic voltammograms changes significantly with the solvent applied in the electrochemical measurements,[E74] which was found to react with the oxidation products during the course of the electrochemical measurements.[E72,73] The ferrocenylated compounds 4 – 6 and 9 show in contrary chemical reversibility. However, only the redox process related to the Fe(CO)3 moiety in complex 5 and to the Fc/Fc+ units are electrochemically reversible.
An anodic shift of the redox potential related to the Fc/Fc+ moiety is observed in 4 (309 mV) and 5 (119 mV) upon coordination of the PPh2(C≡CFc) ligand to the iron-carbonyl unit, indicating decreased electron density at the ferrocenyls iron atoms upon coordination (Table E1).[E19] The observation can be explained by the shift of the electron cloud away from the ferrocenyl moiety via the electron-withdrawing phosphinoacetylide towards the iron-carbonyl. A similar effect of this ligand was also observed in other species featuring platinum,[E16,17] palladium,[E17,19] ruthenium,[E15] or gold[E20] atoms.
In contrary to the effect observed for 4 and 5, a cathodic shift of the Fc/Fc+ redox potential in 6 (71 mV) and 9 (18 mV) was found in relation to uncoordinated 1[E19] (Table E1). This indicates that the introduction of the electron-rich Co2(CO)6 group to the alkynyl unit in 9 and presence of the bridging Fe2(CO)6 moiety in 6 diminishes the withdrawing effect of the phosphinoacetylide on the ferrocenyl group present in the free ligand, and therefore
125 facilitates the Fe2+/Fe3+ oxidation, which in 6 and 9 occurs at lower potential then in the free ligand 1 (Table E1).
Table E1. Cyclic voltammetry data (vs FcH/FcH+, E°’ = 0 V). Measurement conditions: scan rate 100 mV/s, 25 °C, reference decamethylferrocene, concentration of analytes 1.0 mmol∙L−1, electrolyte 0.1 mol·L−1 n solution of [ Bu4N][B(C6F5)4] in dichloromethane.
Epa Epc E°' (ΔEp) Compd. Event in mV in mV in mV
a PPh2(C≡CFc) 161
1 240
4 2 530 410 470 (120)
3 −620
1 150b
5 2 312 248 280 (65)
3 1275
1 128 58 90 (70)
6 2 980
3 1430 1300 1365 (130)
1 185 100 143 (85) 9 2 500 340 420 (160)
a Data taken from reference [E19]; b Data obtained from the square-wave voltammogram.
3 Experimental Section
3.1 Instrumentation
1H (500.3 MHz), 13C{1H} (125.8 MHz) and 31P{1H} NMR (202.5 MHz) spectra were recorded with a Bruker Avance III 500 spectrometer operating at 298 K in the Fourier
transform mode. Chemical shifts are reported in δ units (parts per million) using CDCl3 or
1 13 1 1 CD2Cl2 as solvents (CDCl3: H at 7.26 ppm and C{ H} at 77.16 ppm; CD2Cl2: H at 5.32
13 1 31 1 ppm and C{ H} at 53.8 ppm). P{ H} NMR: external standards 85 % H3PO4, δ = 0.0 ppm;
P(OMe)3, δ = 139.0 ppm. Infrared spectra were recorded with a FT-IR Nicolet 200
126 equipment. The melting points of analytical pure samples (sealed off in nitrogen-purged capillaries) were determined with a Gallenkamp MFB 595 010 M melting point apparatus. Microanalyses were performed using a Thermo FLASHEA 1112 Series instrument. High- resolution mass spectra were performed with a micrOTOF QII Bruker Daltonite workstation.
Suitable crystals of 4 and 6 – 8 were obtained from nhexane solutions containing the respective compounds by cooling them to –30 °C. Crystal data were collected with an Oxford Gemini S diffractometer using graphite-monochromatized Mo Kα radiation (λ = 0.71073 Å, 7) or Cu Kα radiation (λ = 1.54184 Å; 4, 6 and 8). The structures were solved by direct methods and refined by full-matrix least-squares procedures on F2.[E76] All non- hydrogen atoms were refined anisotropically. In case of 6, the rather small and needle-like crystal was twinned. Besides the major domain (ca. 55 % of all reflections), a minor domain (ca. 40 % of all reflections) was observed, with further ca. 5 % of all reflections, which did not form another domain. Data integration was performed with both the major and the minor domain and refined as a 2-component twin. In case of 8, crystals have been made available in form of 8·½ nhexane, whereby nhexane acts as a packing solvent molecule. The asymmetric unit comprises half of the nhexane packing solvent molecule; the other half is generated by crystallographically imposed inversion symmetry. Data of 4 and 6 – 8·½ nhexane have been deposited at the Cambridge Crystallographic Data Centre under CCDC deposition numbers 1475945 – 1475948, respectively.
The electrochemical measurements were performed in anhydrous air free
−1 n dichloromethane solutions containing 0.1 mol L of [ Bu4N][B(C6F5)4] as supporting electrolyte,[E51–67] which were conducted under a blanket of purified argon at 25 °C utilizing a Radiometer Voltalab PGZ 100 electrochemical workstation interfaced with a personal computer. A three electrode cell, featuring a Pt auxiliary electrode, a glassy
2 + −1 carbon working electrode (surface area 0.031 cm ) and an Ag/Ag (0.01 mol L AgNO3) reference electrode mounted on a Luggin capillary was used. The working electrode was pretreated by polishing with a Buehler micro-cloth first with a 1 μm and then with a 1/4 μm diamond paste. The reference electrode was built from a silver wire inserted into a
−1 −1 n solution of 0.01 mol L [AgNO3] and 0.1 mol L of [ Bu4N][B(C6F5)4] in acetonitrile, in a Luggin capillary with a Vycor tip. This Luggin capillary was inserted into a second Luggin capillary with a Vycor tip filled with a 0.1 mol L−1 dichloromethane solution of
n [E77,78] [ Bu4N][B(C6F5)4]. Successive experiments under the same experimental conditions
127 showed that all formal reduction and oxidation potentials were reproducible within ±5 mV. Experimentally potentials were referenced against an Ag/Ag+ reference electrode but results are presented referenced against ferrocene[E79,80] (FcH/FcH+ couple = 220 mV vs
+ [E68] Ag/Ag , ΔEp = 61 mV) as an internal standard as required by IUPAC. Data were then manipulated on a Microsoft Excel worksheet to set the formal redox potentials of the
+ + 2 FcH/FcH couple to E°′ = 0.0 V. Under our conditions the Fc*/Fc* (Fc* = Fe(η -C5Me5)2)
+ [E53] couple was at −614 mV vs FcH/FcH , ΔEp = 60 mV). The cyclic voltammograms were taken after typical two scans and are considered to be steady state cyclic voltammograms in which the potential pattern differs not from the initial sweep.
3.2 General
All reactions were carried out under an atmosphere of argon using standard Schlenk techniques. Tetrahydrofuran was purified by distillation from sodium/benzophenone ketyl. The drying of nhexane, toluene, diethyl ether and dichloromethane was performed with an MBraun MB SPS-800 system (double column solvent filtration, working pressure 0.5 bar).
3.3 Reagents
(Ferrocenylethynyl)diphenylphosphane (1)[E17–19,22] and diironnonacarbonyl (2)[E81] were synthesized according to published procedures. Dicobaltoctacarbonyl (3) was purchased from commercial sources and was used as received.
3.4 Synthesis of 4
Compound 1 (0.887 g, 2.25 mmol) was dissolved in 100 mL of tetrahydrofuran and 0.820 g (2.25 mmol) of 2 were added in a single portion. The reaction mixture was stirred for 4 h at ambient temperature and afterwards all volatiles were removed in vacuum and the crude product was chromatographed (column size: 2.5 x 30 cm, degassed silica, nhexane-diethyl ether mixture of ratio 1:2 (v/v)). The title compound was isolated as an
128 orange fraction. After removal of all volatiles an orange-brown solid was obtained. Yield: 0.922 g (1.64 mmol, 73 % based on 1).
° 1 Mp.: 131 C. H NMR [CDCl3]: 4.24 (s, 5 H, C5H5), 4.32 (pt, JHH = 1.9 Hz, 2 H, Hβ/C5H4), 4.59
(pt, JHH = 1.9 Hz, 2 H, Hα/C5H4), 7.4 - 7.5 (m, 6 H, m,p-C6H5), 7.7 - 7.8 (m, 4 H, o-C6H5) ppm.
13 1 C{ H} NMR [CDCl3]: 61.9 (1 C, Ci/C5H4), 70.2 (2 C, Cβ/C5H4), 70.4 (5 C, C5H5), 72.4 (d, JPC =
0.8 Hz, 2 C, Cα/C5H4), 81.5 (1 C, C≡CFe), 113.2 (1 C, C≡CFe), 128.8 (d, JPC = 11.6 Hz, 4 C, m-
C6H5), 131.1 (d, JPC = 2.6 Hz, 2 C, p-C6H5), 131.9 (d, JPC = 12.2 Hz, 4 C, o-C6H5), 134.5 (d, JPC =
31 1 57.6 Hz, 2 C, Ci/C6H5), 213.1 (d, JPC = 19.4 Hz, 4 C, CO). P{ H} NMR [CDCl3]: 48.8. IR [KBr]: 1918 (s), 1924 (s), 1945 (s), 1972 (s), 2045 (s) (CO), 2159 (s) (C≡C). Elemental Analysis
[%]: calcd. for C28H19Fe2O4P; C, 59.83, H, 3.41; found: C, 59.57, H, 3.58; HR-ESI MS [m/z]: calcd. for M-H+ 562.9793, found 562.9818.
–1 Crystal data of 4. C28H19Fe2O4P, M = 562.10 g·mol , crystal colour/shape/dimension:
3 orange/block/0.38 × 0.3 × 0.3 mm , monoclinic, P21/n, a = 12.2376(3) Å, b = 14.0281(3)
3 -3 Å, c = 14.7589(3) Å, β = 106.311(2) °, V = 2431.69(10) Å , Z = 4, ρcalcd = 1.535 g∙cm , T = 100 K, Cu Kα radiation (wavelength 1.54184 Å), θ range 4.161 – 64.996 °, reflections collected/independent: 10023/4129, data/restraints/parameters: 4129/0/316, Rint =
0.0318, R1 = 0.0369, wR2 = 0.0883 (I > 2σ(I)).
3.5 Synthesis of 4, 5 and 6
In contrast to the synthesis of 4 (see above), the reaction of 1 (1.68 g, 4.26 mmol) with 2 (1.55 g, 4.26 mmol) was performed in 100 mL of tetrahydrofuran at 50 °C for 14 h. Afterwards, all volatiles were removed in vacuum and the crude material obtained was chromatographed (column size: 3 x 25 cm, degassed alumina, mixture of nhexane-diethyl ether of ratio 3:1 (v/v)). Three fractions were obtained.
1st Fraction: After removal of all volatiles and recrystallization from nhexane, dark red crystals of 6 could be isolated. Yield: 0.120 g (0.18 mmol, 4 % based on 1). Mp.: 180 °C
1 (decomp.). H NMR [CDCl3]: 3.73 (pt, JHH = 1.9 Hz, 2 H, Hβ/C5H4), 4.04 (s, 5 H, C5H5), 4.06
(pt, JHH = 1.9 Hz, 2 H, Hα/C5H4), 7.2 - 7.3 (m, 2 H, p-C6H5), 7.3 - 7.4 (m, 4 H, m-C6H5), 7.5 - 7.6
13 1 (m, 4 H, o-C6H5). C{ H} NMR [CDCl3]: 67.9 (d, JPC = 3.0 Hz, 1 C, Ci/C5H4), 69.1 (2 C,
Cβ/C5H4), 70.3 (5 C, C5H5), 71.4 (d, JPC = 1.9 Hz, 2 C, Cα/C5H4), 93.2 (d, JPC = 7.3 Hz, 1 C,
C≡CFe), 103.0 (d, JPC = 54.2 Hz, 1 C, C≡CFe), 127.9 (d, JPC = 10.4 Hz, 2 C, o-C6H5), 128.7 (d,
129 JPC = 9.4 Hz, 2 C, o-C6H5), 129.6 (d, JPC = 3.1 Hz, 1 C, p-C6H5), 130.3 (d, JPC = 2.4 Hz, 1 C, p-
C6H5), 133.3 (d, JPC = 8.2 Hz, 2 C, m-C6H5), 134.5 (d, JPC = 7.7 Hz, 2 C, m-C6H5), 135.0 (d, JPC =
31 1 33.6 Hz, 1 C, Ci/C6H5), 138.8 (d, JPC = 24.9 Hz, 1C, Ci/C6H5), 210.4 (s, 6 C, CO). P{ H} NMR
[CDCl3]: 147.7. IR [KBr]: 1961 (s), 1994 (s, broad), 2029 (s), 2067 (s) (CO). Elemental
analysis [%]: calcd. for C30H19Fe3O6P; C, 53.46, H, 2.84; found: C, 53.86, H, 2.60. HR-ESI MS [m/z]: calcd. for M+- 2CO 617.9065, found 617.9067, calcd. for M+- 3CO 589.9116, found 589.9123, calcd. for M+- 5CO 533.9217, found 533.9219.
–1 Crystal data of 6. C30H19Fe3O6P, M = 673.97 g·mol , crystal colour/shape/dimension: orange/needle/0.2 × 0.06 × 0.04 mm3, triclinic, P-1, a = 10.2592(13) Å, b = 10.9473(11) Å, c = 14.6831(13) Å, α = 70.533(9) °, β = 75.882(9) °, γ = 64.470(12) °, V = 1393.2(3) Å3, Z =
-3 2, ρcalcd = 1.607 g∙cm , T = 110 K, Cu Kα radiation (wavelength 1.54184 Å), θ range 4.637 – 61.868 °, reflections collected/independent: 11230/7683, data/restraints/parameters:
7683/453/362, Rint = 0.1073, R1 = 0.0814, wR2 = 0.2094 (I > 2σ(I)).
2nd Fraction: Eluent, mixture of nhexane-diethyl ether of ratio 3:1 (v/v). After evaporation of all volatiles in vacuum, 4 could be isolated as an orange-brown solid. Yield: 2.03 g (3.61 mmol, 84 % based on 1). For spectroscopic data see earlier.
3rd Fraction: Eluent, mixture of nhexane-diethyl ether of ratio 1:1 (v/v). After removal of all volatiles in vacuum, 5 could be isolated as a bright yellow solid. Yield: 0.186 g (0.200
° 1 mmol, 5 % based on 2). Mp.: 105 C; H NMR [CD2Cl2]: 4.26 (s, 10 H, C5H5), 4.30 (pt, JHH =
1.9 Hz, 4 H, Hβ/C5H4), 4.59 (pt, JHH = 1.9 Hz, 4 H, Hα/C5H4), 7.4 – 7.5 (m, 12 H, m,p-C6H5), 7.9
13 1 – 8.0 (m, 4H, o-C6H5). C{ H} NMR [CD2Cl2]: 63.2 (2 C, Ci/C5H4), 70.4 (4 C, Cβ/C5H4), 70.8
(10 C, C5H5), 70.9 (2 C, C≡CFe), 72.7 (4 C, Cα/C5H4), 111.6 (2 C, C≡CFe), 129.0 (t, JPC = 5.4
Hz, 8 C, m-C6H5), 130.8 (s, 4 C, p-C6H5), 132.4 (t, JPC = 6.3 Hz, 8 C, o-C6H5), 137.6 (t, JPC =
31 1 27.3 Hz, 4 C, Ci/C6H5), 214.0 (t, JPC = 29.8 Hz, 3 C, CO). P{ H} NMR [CD2Cl2]: δ = 58.2;
-1 [CDCl3]: 58.8. IR [KBr]: 1881 (s, broad), 1973 (vw) (CO), 2156 (m) (C≡C) cm . Elemental
-1 analysis [%]: calcd. for C51H38Fe3O3P2 (928.328 g mol ); C, 65.95, H, 4.13, found C, 65.83,
+ H, 4.50. HR-ESI MS [m/z]: calcd. for (FcC2PPh2)2FeOH 861.0522, found: 861.0480; calcd.
+ for FcC2PPh2FeH 411.0596, found: 411.0573; calcd. for FcC2PPh2 394.0569, found: 394.0559.
130 3.6 Synthesis of 6 by reacting 4 with 2
Compound 4 (0.461 g, 0.82 mmol) was dissolved in 120 mL of toluene and 0.286 g (0.79 mmol) of 2 were added in a single portion. After stirring this mixture for 3 h under reflux it was cooled to ambient temperature and all volatiles were removed in vacuum. The obtained crude product was purified by column chromatography (alumina, column size: 2 x 30 cm) using a mixture of nhexane-diethyl ether of ratio 2:1 (v/v). After evaporation of all volatile materials, compound 6 was obtained as a red crystalline solid in a yield of 0.335 g (0.497 mmol, 63 % based on 2). With the same eluent a 2nd fraction could be obtained, from which unreacted 4 could be isolated (yield: 0.16 g, 0.28 mmol, 35 % based on 4). For spectroscopic and analytic date of 4 and 6 see above.
3.7 Synthesis of 7 and 8
Dicobaltoctacarbonyl (3) (0.490 g, 1.44 mmol) was dissolved in 50 mL of a nhexane- toluene mixture of ratio 1:1 (v/v). This solution was slowly added over 1 h to 1 (0.516 g, 1.31 mmol) dissolved in 100 mL of the same solvent mixture at ambient temperature. Stirring was continued for 3 h. Afterwards, all volatiles were removed in vacuum and the crude product was chromatographed on degassed silica (column size: 4 x 23 cm).
Compound 7. With a mixture of nhexane-diethyl ether of ratio 4:1 (v/v) a green fraction could be eluted from which after removal of all volatiles compound 7 could be isolated in form of a green crystalline solid. Yield: 0.214 g (0.314 mmol, 24 % based on 1).
o 1 Mp.: 150 C (decomp.). H NMR [CDCl3]: 4.26 (s, 5 H, C5H5), 4.36 (pt, JHH = 1.8 Hz, 2 H,
Hβ/C5H4), 4.39 (pt, JHH = 1.8 Hz, 2 H, Hα/C5H4), 7.4 - 7.5 (m, 6 H, m,p-C6H5), 7.7 - 7.8 (m, 4 H,
31 1 o-C6H5). P{ H} NMR [CDCl3]: 0.28. IR [KBr]: 1957 (s), 2005 (s, broad), 2030 (s), 2056 (s), 2086 (m) (CO). HR-ESI MS [m/z]: calcd. for MH+-CO 652.9057, found 652.9061; calcd. for MH+-3CO 596.9158, found 596.9154.
–1 Crystal data of 7. C30H19Co2FeO6P, M = 680.13 g·mol , crystal colour/shape/
3 dimension: block/green/0.34 × 0.34 × 0.30 mm , monoclinic, P21/n, a = 13.5322(3) Å, b =
3 14.7581(3) Å, c = 13.7939(3) Å, β = 91.779(2) °, V = 2753.45(10) Å , Z = 4, ρcalcd = 1.641 g∙cm–3, T = 100 K, Mo Kα radiation (wavelength 0.71073 Å), θ range 3.131 – 25.00 °,
131 reflections collected/independent: 11713/4804, data/restraints/parameters: 4804/0/
361, Rint = 0.0395, R1 = 0.0332, wR2 = 0.0694 (I > 2σ(I)).
Compound 8. With a nhexane-diethyl ether mixture of ratio 1:1 (v/v) a 2nd dark olive- green fraction could be eluted from which, after removal of all volatiles, 8 was isolated. Yield: 91.2 mg (0.0917 mmol, 7 % based on 1).
o 1 Mp.: 100 C (decomp.). H NMR [CDCl3]: 4.14 (s, 5 H, C5H5), 4.35 (m, 4 H, C5H4), 7.5 - 7.6
13 1 (m, 6 H, m,p-C6H5), 8.1 (m, 4 H, o-C6H5). C{ H} NMR [CDCl3]: 69.7 (2 C, Cβ/C5H4), 70.1 (5
C, C5H5), 70.5 (C, Ci/C5H4), 70.7 (2 C, Cα/C5H4), 128.6 (d, JPC = 12.1 Hz, 4 C, o-C6H5), 131.5
(d, JPC = 9.2 Hz, 4 C, m-C6H5), 132.2 (d, JPC = 6.4 Hz, 2 C, p-C6H5), 133.7 (d, JPC = 107.0 Hz, 2 C,
31 1 Ci/C6H5), 198.3 (d, JPC = 9.8, CO). P{ H} NMR [CDCl3]: 21.9. IR [KBr]: 1540 (m), 1850 (m), 1969 (s), 1980 (s), 1990 (s), 1998 (s), 2009 (s), 2018 (s), 2028 (s, broad) and 2065 (s)
(CO). Elemental analysis [%] calcd. for C37H19Co4FeO13P; C, 44.68, H, 1.93, found C, 44.34, H, 2.24.
–1 Crystal data of 8. C77H45Co8Fe2O26P4, M = 2031.21 g·mol , crystal colour/shape/ dimension: block/black/0.3 × 0.2 × 0.2 mm3, triclinic, P-1, a = 10.2849(6) Å, b = 11.2011(6) Å, c = 19.2964(10) Å, α = 76.289(4) °, β = 78.424(5) °, γ = 74.071(5) °, V =
3 –3 2054.7(2) Å , Z = 1, ρcalcd = 1.642 g∙cm , T = 117 K, Cu Kα radiation (wavelength 1.54184 Å), θ range 4.183 – 62.935 °, reflections collected/independent: 11519/6487,
data/restraints/parameters: 6487/591/502, Rint = 0.0346, R1 = 0.0440, wR2 = 0.1063 (I > 2σ(I)).
3.8 Synthesis of 8 from 1 with 3
Under similar reaction conditions described above, 1 (0.258 g, 0.655 mmol) was reacted with 3 (0.447 g, 1.31 mmol). The thus obtained crude product was chromatographed on silica (column size: 4 x 20 cm). The title compound was eluted with a nhexane-diethyl ether mixture of 4:1 to 1:1 (v/v). After evaporation of all volatiles, 8 was obtained as a dark crystalline solid in a yield of 0.300 g (0.301 mmol, 46 % based on 1). For spectroscopic and analytic data of 8 see above.
132 3.9 Synthesis of 9 in the reaction of 7 with 2
Compound 7 (0.150 g, 0.220 mmol) was dissolved in 50 mL of anhydrous tetrahydrofuran and 87.3 mg (0.240 mmol) of 2 were added in a single portion. The mixture was stirred for 3 h at 50 oC, cooled to ambient temperature, followed by evaporation of all volatiles in vacuum. The obtained crude product was purified by column chromatography (silica, column size: 2 x 30 cm) using a mixture of nhexane- dichlorometane of ratio 2:1 (v/v). After evaporation of all volatiles and recrystallization from diethyl ether at ambient temperature, compound 9 was obtained as a dark crystalline solid. Yield: 0.166 g (0.196 mmol, 89 % based on 7).
° 1 Mp.: 130 C (decomp.). H NMR [CDCl3]: 4.30 (s, 5 H, C5H5), 4.43 (pt, JHH = 1.8 Hz, 2 H,
Hβ/C5H4), 4.52 (pt, JHH = 1.8 Hz, 2 H, Hα/C5H4), 7.4 (m, 4 H, m-C6H5), 7.5 (m, 2 H, p-C6H5),
13 1 7.6 (m, 4 H, o-C6H5). C{ H} NMR [CDCl3]: 69.1 (2 C, Cβ/C5H4), 69.9 (5 C, C5H5), 72.5 (2 C,
Cα/C5H4), 87.7 (C, Ci/C5H4), 128.3 (d, JPC = 10.5 Hz, 4 C, m-C6H5), 131.1 (d, JPC = 2.4 Hz, 2 C, p-C6H5), 133.2 (d, JPC = 10.7 Hz, 4 C, o-C6H5), 135.9 (d, JPC = 51.2 Hz, 2 C, Ci/C6H5), 198.8 (6
31 1 C, CO(Co)), 213.7 (d, JPC = 17.3 Hz, 4 C, CO(Fe)). P{ H} NMR [CDCl3]: 76.1. IR [KBr]: 1872 (m, broad), 1925 (s), 1946 (s), 1962 (m), 2030 (s, broad), 2060 (s, broad), 2090 (s) (CO).
Elemental analysis [%]: calcd. for C54H39Co4Fe2O16P2; C, 48.15, H, 2.26, found C, 48.42, H, 2.76. HR-ESI MS [m/z]: calcd. for M+-2CO 791.8159, found 791.8176; calcd. for M+-3CO 763.8116, found 763.8227; calcd. for M+-4CO 735.8231, found 735.8277.
3.10 Synthesis of 9 in the reaction of 4 with 3
Compound 4 (1.17g, 2.09 mmol) was dissolved in 150 mL of a toluene-nhexane mixture of ratio 1:1 (v/v) and 0.787 g (2.30 mmol) of 3 dissolved in 50 mL of the same solvent mixture were added dropwise over 1 h. After 2 h of stirring at ambient temperature the initially orange solution became dark green. After evaporation of all volatiles in vacuum, the crude product was dissolved in 15 mL of a nhexane-dichloromethane mixture of ratio 9:1 (v/v) and was purified by column chromatography (column size: 3 x 25 cm, silica). With a mixture of nhexane-dichloromethane of ratio 2:1 (v/v) a olive-green fraction could be collected from which after evaporation of all volatiles and recrystallization of the obtained solid from diethyl ether at ambient temperature dark crystals of 9 could be
133 isolated. Yield: 1.34 g (1.58 mmol, 76 % based on 4). For spectroscopic and analytic data see earlier.
4 Electronic Supplementary Material (Supporting information)
Supporting information (Infra-Red Spectra, NMR Spectra, cyclic voltammograms, crystal and intensity collection data) for this article is available on the WWW under http://dx.doi.org/10.1016/j.jorganchem.2016.11.034. Crystallographic data of 4, 6, 7 and 8 are also available from the Cambridge Crystallographic Data Centre under CCDC deposition numbers 1475945 – 1475948, respectively
5 References
[E1] W. F. Smith, J. Yule, N. J. Taylor, H. N. Paik, A. J. Carty, Inorg. Chem. 1977, 16, 1593– 1600.
[E2] A. A. Cherkas, L. H. Randall, S. A. Maclaughlin, G. N. Mott, N. J. Taylor, A. J. Carty, Organometallics 1988, 7, 969–977.
[E3] H. Lang, L. Zsolnai, J. Organomet. Chem. 1989, 369, 131–135.
[E4] H. A. Patel, R. G. Fischer, A. J. Carty, D. V Naik, G. J. Palenik, J. Organomet. Chem. 1973, 60, 49–52.
[E5] H. A. Patel, A. J. Carty, N. K. Hota, J. Organomet. Chem. 1973, 50, 247–263.
[E6] H. N. Paik, A. J. Carty, K. Dymock, G. J. Palenik, J. Organomet. Chem. 1974, 70, 17–20.
[E7] E. C. Constable, C. E. Housecroft, M. Neuburger, M. Zehnder, Organometallics 1999, 18, 2565–2567.
[E8] N. Kuhn, M. Göhner, M. Steinmann, Z. Naturforsch. 2001, 56 b, 95–99.
[E9] A. Hengefeld, J. Kopf, D. Rehder, Organometallics 1983, 2, 114–121.
[E10] A. J. Carty, Pure Appl. Chem. 1982, 54, 113–130.
[E11] E. Sappa, A. Tiripicchio, P. Braunstein, Coord. Chem. Rev. 1985, 65, 219–284.
[E12] R. B. King, A. Efraty, Inorg. Chim. Acta 1970, 4, 319–323.
[E13] K. Heinze, H. Lang, Organometallics 2013, 32, 5623–5625.
134 [E14] B. Milde, T. Rüffer, H. Lang, Inorganica Chim. Acta 2012, 387, 338–345.
[E15] J. Berenguer, M. Bernechea, J. Fernández, B. Gil, E. Lalinde, M. T. Moreno, S. Ruiz, S. Sánchez, Organometallics 2011, 30, 4665–4677.
[E16] Á. Díez, E. Lalinde, M. T. Moreno, S. Sánchez, Dalt. Trans. 2009, 3434–3446.
[E17] T. Baumgartner, M. Fiege, F. Pontzen, R. Arteaga-Müller, Organometallics 2006, 25, 5657–5664.
[E18] A. Jakob, B. Milde, P. Ecorchard, C. Schreiner, H. Lang, J. Organomet. Chem. 2008, 693, 3821–3830.
[E19] B. Milde, D. Schaarschmidt, P. Ecorchard, H. Lang, J. Organomet. Chem. 2012, 706- 707, 52–65.
[E20] A. Jakob, P. Ecorchard, M. Linseis, R. F. Winter, H. Lang, J. Organomet. Chem. 2009, 694, 655–666.
[E21] E. Fourie, E. Erasmus, J. C. Swarts, A. Jakob, H. Lang, G. K. Joone, C. E. J. Van Rensburg, Anticancer Res. 2011, 31, 825–830.
[E22] A. J. Carty, N. K. Hota, T. W. Ng, H. A. Patel, T. J. O’Connor, Can. J. Chem. 1971, 49, 2706–2711.
[E23] H. Lang, U. Lay, J. Organomet. Chem. 1990, 388, C1–C4.
[E24] U. Lay, H. Lang, J. Organomet. Chem. 1991, 418, 79–89.
[E25] H. Lang, U. Lay, J. Organomet. Chem. 1992, 441, 389–396.
[E26] H. Lang, M. Leise, L. Zsolnai, J. Organomet. Chem. 1990, 386, 349–363.
[E27] H. Lang, M. Leise, L. Zsolnai, J. Organomet. Chem. 1991, 410, 379–388.
[E28] C. Georgi, A. Hildebrandt, A. Tuchscherer, S. Oswald, H. Lang, Z. Anorg. Allg. Chem. 2013, 639, 2532–2535.
[E29] C. Georgi, A. Hildebrandt, T. Waechtler, S. E. Schulz, T. Gessner, H. Lang, J. Mater. Chem. C 2014, 2, 4676–4682.
[E30] C. Georgi, M. Hapke, I. Thiel, A. Hildebrandt, T. Waechtler, S. E. Schulz, H. Lang, Thin Solid Films 2015, 578, 180–184.
[E31] P. Szabó, L. Fekete, G. Bor, Z. Nagy-Magos, L. Markó, J. Organomet. Chem. 1968, 12, 245–248.
[E32] M. J. Mays, K. Sarveswaran, G. A. Solan, Inorg. Chim. Acta 2003, 354, 21–28.
[E33] T. S. Barnard, M. R. Mason, Inorg. Chem. 2001, 40, 5001–5009.
[E34] J. E. Huheey, E. A. Keiter, R. L. Keiter, Inorganic Chemistry: Principles of Structure and Reactivity, HarpesCollins College Publishers, New York, 1993.
[E35] E. Louattani, J. Suades, A. Alvarez-larena, J. F. Piniella, G. Germain, J. Organomet. Chem. 1996, 506, 121–127.
135 [E36] D. Nucciarone, S. A. MacLaughlin, N. J. Taylor, A. J. Carty, Organometallics 1988, 7, 106–117.
[E37] P. T. Snee, C. K. Payne, S. D. Mebane, K. T. Kotz, C. B. Harris, J. Am. Chem. Soc. 2001, 123, 6909–6915.
[E38] L. R. Martin, F. W. B. Einstein, R. K. Pomeroy, Inorg. Chem. 1985, 24, 2777–2785.
[E39] C. Elschenbreuch, Organometalchemie, Taubner Verlag, Wiesbaden, 2008.
[E40] H. Lang, Reactionen von Komplexgebundenen Phosphanen, Konstanzer Dissertationen, Hartung-Gorre Verlag, Konstanz, 1985.
[E41] A. J. Carty, H. N. Paik, G. J. Palenik, Inorg. Chem. 1977, 16, 300–305.
[E42] M. van Rentergem, G. P. van der Kelen, E. C. Claeys, J. Mol. Struct. 1982, 80, 317– 324.
[E43] C. D. Pribula, T. L. Brown, E. Münck, J. Am. Chem. Soc. 1974, 96, 4149–4154.
[E44] R. Costa, A. Garcia, J. Ribas, T. Mallah, Y. Journaux, J. Sletten, X. Solans, V. Rodríguez, Inorg. Chem. 1993, 32, 3733–3742.
[E45] P. E. Riley, R. E. Davis, Inorg. Chem. 1980, 19, 159–165.
[E46] P. Štepnička, J. Organomet. Chem. 2008, 693, 297–306.
[E47] C. J. Adams, M. I. Bruce, E. Horn, E. R. T. Tiekink, J. Chem. Soc. Dalt. Trans. 1992, 1157–1164.
[E48] G. G. Sumner, H. P. Klug, L. E. Alexander, Acta Cryst. 1964, 17, 732–742.
[E49] T. Y. Garcia, J. C. Fettinger, M. M. Olmstead, A. L. Balch, Chem. Commun. 2009, 7143– 7145.
[E50] N. Ungvári, E. Fördos, J. Balogh, T. Kégl, L. Párkányi, F. Ungváry, Organometallics 2010, 29, 3837–3851.
[E51] R. J. LeSuer, C. Buttolph, W. E. Geiger, Anal. Chem. 2004, 76, 6395–6401.
[E52] F. Barrière, W. E. Geiger, J. Am. Chem. Soc. 2006, 128, 3980–3989.
[53] A. Nafady, W. E. Geiger, Organometallics 2008, 27, 5624–5631.
[E54] J. M. Speck, M. Korb, A. Schade, S. Spange, H. Lang, Organometallics 2015, 34, 3788– 3798.
[E55] U. Pfaff, G. Filipczyk, A. Hildebrandt, M. Korb, H. Lang, Dalton Trans. 2014, 43, 16310–16321.
[E56] S. W. Lehrich, A. Hildebrandt, M. Korb, H. Lang, J. Organomet. Chem. 2015, 1–9.
[E57] S. W. Lehrich, A. Hildebrandt, T. Rüffer, M. Korb, P. J. Low, H. Lang, Organometallics 2014, 33, 4836–4845.
[E58] J. M. Speck, M. Korb, T. Rüffer, A. Hildebrandt, H. Lang, Organometallics 2014, 33, 4813–4823.
136 [E59] A. Hildebrandt, D. Schaarschmidt, R. Claus, H. Lang, Inorg. Chem. 2011, 50, 10623– 10632.
[E60] U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Rüffer, P. J. Low, H. Lang, T. Rüffer, P. J. Low, H. Lang, Organometallics 2013, 32, 6106–6117.
[E61] D. Miesel, A. Hildebrandt, M. Korb, P. J. Low, H. Lang, Organometallics 2013, 32, 2993–3002.
[E62] U. Pfaff, A. Hildebrandt, D. Schaarschmidt, T. Hahn, S. Liebing, J. Kortus, H. Lang, Organometallics 2012, 31, 6761–6771.
[E63] J. M. Speck, R. Claus, A. Hildebrandt, T. Rüffer, E. Erasmus, L. van As, J. C. Swarts, H. Lang, Organometallics 2012, 31, 6373–6380.
[E64] D. Miesel, A. Hildebrandt, M. Korb, D. Schaarschmidt, H. Lang, Organometallics 2015, 34, 4293–4304.
[E65] D. Miesel, A. Hildebrandt, M. Korb, H. Lang, J. Organomet. Chem. 2016, 803, 104– 110.
[E66] D. Schaarschmidt, A. Hildebrandt, S. Bock, H. Lang, J. Organomet. Chem. 2014, 751, 742–753.
[E67] W. E. Geiger, F. Barrière, Acc. Chem. Res. 2010, 43, 1030–1039.
[E68] G. Gritzner, J. Kuta, Pure Appl. Chem. 1984, 56, 461–466.
[E69] N. Avarvari, D. Martin, M. Fourmigué, J. Organomet. Chem. 2002, 643-644, 292–300.
[E70] C. Gouverd, F. Biaso, L. Cataldo, T. Berclaz, M. Geoffroy, E. Levillain, N. Avarvari, M. Fourmigué, F. X. Sauvage, C. Wartelle, Phys. Chem. Chem. Phys. 2005, 7, 85–93.
[E71] A. M. Bond, P. A. Dawson, B. M. Peake, B. H. Robinson, J. Simpson, Inorg. Chem. 1977, 16, 2199–2206.
[E72] S. W. Blanch, A. M. Bond, R. Colton, Inorg. Chem. 1981, 20, 755–761.
[E73] R. N. Bagchi, A. M. Bond, C. L. Heggie, T. L. Henderson, E. Mocellin, R. A. Seikel, Inorg. Chem. 1983, 22, 3007–3012.
[E74] J. J. Adams, O. J. Curnow, G. Huttner, S. J. Smail, M. M. Turnbull, J. Organomet. Chem. 1999, 577, 44–57.
[E75] P. Mathur, D. K. Rai, R. S. Ji, B. Pathak, S. Boodida, S. M. Mobin, RSC Adv. 2013, 3, 26025.
[E76] G. M. Sheldrick, Acta Crystallogr. Sect. A Found. Crystallogr. 2007, 64, 112–122.
[E77] M. D. Rausch, I. Bernal, B. R. Davies, A. Siegel, F. A. Higbie, G. F. Westover, J. Coord. Chem. 1973, 3, 149–159.
[E78] A. Clearfield, R. Gopal, M. D. Rausch, E. F. Tokas, F. A. Higbie, I. Bernal, J. Organomet. Chem. 1977, 135, 229–248.
[E79] I. Noviandri, K. N. Brown, D. S. Fleming, P. T. Gulyas, P. A. Lay, A. F. Masters, L. Phillips, J. Phys. Chem. B 1999, 103, 6713–6722.
137 [E80] J. R. Aranzaes, M.-C. Daniel, D. Astruc, Can. J. Chem. 2006, 84, 288–299.
[E81] D. F. Keeley, R. E. Johnson, J. Inorg. Nucl. Chem. 1959, 11, 33–41.
138 CHAPTER F Summary
The submitted PhD thesis describes the synthesis, characterization and structural elucidation of novel perferrocenylated cyclic complexes, which were obtained via [2+2]
5 5 5 and [2+2+2] cyclomerization of FcC≡C–C≡CFc (Fc = Fe(η -C5H4)(η -C5H5)) utilizing Co(η -
C5H5)(CO)2. The optimization of the reaction conditions was undertaken in order to maximize the yield of three specific families of compounds by (I) cyclodimerization, (II) cyclodimerization with CO insertion and (III) cyclotrimerization including C–H bond activation.
Furthermore, diverse reaction patterns of the (ferrocenylethynyl)diphenylphosphane ligand were applied to form ferrocenylated phosphino-alkynide complexes with diironnonacarbonyl and dicobaltoctacarbonyl as reagents. Structural, chemical, and physical properties of these compounds were investigated.
The research results obtained are presented in chapters C – E.
Chapter C: Multiferrocenyl Cobalt-based Sandwich Compounds
Chapter D: Combining Cobalt-Assisted Alkyne Cyclotrimerization and Ring Formation through C–H Bond Activation: A “One-Pot” Approach to Complex Multimetallic Structures
Chapter E: Coordination Behavior of (Ferrocenylethynyl)diphenylphosphane Towards Binuclear Iron and Cobalt Carbonyls
1 Conclusions of Chapter C (Appendix A)
G. Filipczyk, S. W. Lehrich, A. Hildebrandt, T. Rüffer, D. Schaarschmidt, M. Korb, H. Lang, Eur. J. Inorg. Chem., 2017, 263–275.
A “one-pot” synthetic methodology for the preparation of cobalt-coordinated cyclobutadienes (3a,b, 4a,b), cyclopentadienones (6a–c), and multiferrocenyl benzenes (5a–c) (Figure C1) as a result of cyclodi- and cyclotrimerization including C–H activation (5) of 1,4-diferrocenylbutadiyne (1) with dicarbonyl(η5-cyclopentadienyl)cobalt (2) and CO insertion into Co–C bonds (6, 7) is discussed. Adjustment of the reaction conditions
139 and the use of different ratios of the respective reagents allowed the formation of the different compound families. In this respect, eleven ferrocenyl-functionalized compounds could be separated by column chromatography and have been characterized by NMR, UV/Vis, and IR spectroscopy, high-resolution ESI-TOF mass spectrometry, and elemental analysis. The molecular structures of 3a,b, 4a, 6a, and 7 in the solid state were determined by single-crystal X-ray diffraction studies, whereby the ferrocenyl groups display an eclipsed conformation, with exception of 4a in which two ferrocenyl units adopt a staggered conformation. Due to steric hindrance, the two η4-coordinated moieties in 4a and 7 are rotated by 56.4(2) (4a) and 65.9(2)° (7) away from each other.
FcC C C CFc + Co 3 - 7 OC CO 1 2
5 5 5 Figure C1. Reaction of FcC≡C–C≡CFc (Fc = Fe(η -C5H4)(η -C5H5)) (1) with Co(η -C5H5)(CO)2 (2) affording 3 – 7. For 5a,b see Chapter D (compounds 3a,b) and reference [C34].
The electronic properties of 3a, 5c, 6a–c, and 7 were determined by using cyclic and square-wave voltammetry. The cyclic voltammogram of 3a and 6a–c show four individual redox events, whereas for 5c and 7 six partially overlapping, reversible one-electron redox processes are characteristic. Oxidation of 5c to 5c2+ and the oxidation of 73+ to 75+ occur in a very close potential range. Other oxidation events are well separated. Further investigations of the thus formed mixed-valent species featuring FeII/FeIII centers were achieved by in situ UV/Vis/NIR spectroelectrochemistry (3a and 6a–c). Mixed-valent
140 species were formed for 3a, from which 3a+ showed two IVCT absorptions at 7400 cm–1 (ε
–1 –1 –1 –1 –1 –1 = 930 L mol cm , Δṽ1/2 = 5350 cm ) and at 4800 cm (ε = 230 L mol cm , Δṽ1/2 = 2000 cm–1), due to a charge transfer between ferrocenium–ferrocene and ferrocenium– ethynylferrocene units, respectively, and one LMCT band at 3900 cm–1 (ε = 580 L mol–1
–1 –1 2+ –1 cm , Δṽ1/2 = 1200 cm ), whereas for 3a only one IVCT absorption at 6100 cm (ε = 300
–1 –1 –1 2+ L mol cm , Δṽ1/2 = 3150 cm ) is characteristic. In the 3a species, both ferrocenyl units are oxidized; therefore, only a charge transfer between ferrocenium–ethynylferrocene moieties occurs. Mixed-valent species 3a+ and 3a2+ have been classified as weakly coupled class II systems according to the classification of Robin and Day.[C82] The sandwich
4 5 compound Co(η -C4Fc4)(η -C5H5), with its four ferrocenyl units, shows a similar behavior
[C64,65] and could be classified as class II system. In contrast, in 1,3,5-Fc3-2,4,6-(FcC≡C)3-
[C49] + C6, no electronic interaction between the neighboring Fc /FcC≡C redox centers was
+ found, but only between the Fc /Fc termini across the C6-ring, which was confirmed by the appearance of only a single IVCT band.
It was observed that cyclopentadienones 6a–c decompose during stepwise oxidation. When the potential was increased from 400 to 600 mV an abrupt change in the UV/Vis spectra was observed, with no absorption in the NIR region. In contrast to the cyclobutadiene core in 3a, despite a good separation between the individual redox events, an increase of the potential did not succeed in a charge-transfer between the FeII/FeIII centers across the cyclopentadienone core, caused by the presence of the electron- withdrawing carbonyl functionality in this linkage unit, which makes it more electron- pure and unable to facilitate the charge-transfer process. Cyclopentadienones 6a–c are examples of the so called “pretenders”,[C67] for which the half-wave potential splitting value is not a good measure of the electronic coupling in the mixed-valent systems.
2 Conclusions of Chapter D (Appendix B)
G. Filipczyk, A. Hildebrandt, U. Pfaff, M. Korb, T. Rüffer, H. Lang, Eur. J. Inorg. Chem. 2014, 4258–4262.
Novel multiferrocenyl-substituted benzenes have been synthesized starting from 1,4- diferrocenylbutadiyne as the only substrate in the presence of substoichiometric amounts
141 of [CpCo(CO)2]. The reaction combines a cobalt-assisted [2+2+2] cycloaddition and C–H bond activation using the same catalyst as demonstrated by model reactions. Hexa- ferrocenyl 3 belongs to the family of multiferrocenyl aromatic compounds which are rather scarcely developed. Within this family, it is the first example in which the ferrocenyl units are either 1,2 substituted to form a five-membered cycle attached to the
benzene core or σ-bonded through a C5H4 cyclopentadienyl unit. Electrochemical studies showed that for 3a all six ferrocenyl moieties could be oxidized consecutively, whereas only four individual redox events could be observed for symmetric 3b owing to poor solubility. In-situ spectro-electrochemical measurements of mixed-valent 3a3+ and 3b3+ indicate that two possible intervalence charge-transfer pathways contribute to the excitation within the NIR region. One IVCT absorption resembles those found for 1,2- diferrocenylethylenes, whereas the second IVCT band is similar to those found in 1,3,5- triferrocenylbenzene.
Fc Fe Fe HC
H C Fc CH Fe Fc 3a 3b
3 Conclusions of Chapter E (Appendix C)
G. Filipczyk, A. Hildebrandt, T. Rüffer, M. Korb, H. Lang, J. Organomet. Chem., 2017, 142– 151.
5 5 The reaction chemistry of PPh2(C≡CFc) (Fc = Fe(η -C5H4)(η -C5H5)) (1) with the
binary metal carbonyls Fe2(CO)9 (2) and Co2(CO)8 (3) is described. Within these reactions
organometallic compounds Fe(CO)4(PPh2(C≡CFc)) (4), Fe(CO)3(PPh2(C≡CFc))2 (5),
2 2 Fe2(CO)6(µ,η -C≡CFc)(µ-PPh2) (6) (reaction of 1 with 2), PPh2((η -C≡CFc)Co2(CO)6) (7)
2 and Co2(CO)7(PPh2((η -C≡CFc)Co2(CO)6)) (8) (reaction of 1 with 3) could be obtained.
2 When 4 was reacted with 1 equivalent of 3 then Fe(CO)4(PPh2((η -C≡CFc)Co2(CO)6)) (9) was formed. The latter compound is also accessible when 7 is treated with 2.
142
Scheme E1. Synthesis of 4 – 6 from 1 and 2.
Scheme E2. Synthesis of 7 – 9.
The structures of 4 and 6–8 in the solid state were determined by single X-ray structure analysis. These studies verified that in dependency of the reaction conditions, the course of the reaction and the nature of reactant 1 acts very flexible as a ligand in a κP fashion in 4, in a µ-κC:κC’ coordination in 7 and 8 and additionally for 8 in a κP mode. At elaborated temperatures a P–C bond cleavage in 1 occurred by forming organometallic 6. The mechanism for this reaction is published elsewhere.[E1,10]
The electrochemical behavior of 4–6 and 9 was determined by cyclic and square-wave voltammetry. Reversible redox events were observed for the Fc units. Also the Fe(CO)3 moiety supported by two coordinated PPh2(C≡CFc) ligands in 5 shows electrochemical reversibility. The E°′ values related to the Fc/Fc+ redox couple for 4 and 5 are anodically
143 shifted by 309 and 119 mV, respectively, as compared to the value for the appropriate redox-couple in 1. In contrary, a cathodically shifted redox potential was observed for 6
and 9 (71, 18 mV) of which the electron-rich Fe2(CO)6 or Co2(CO)6 bridging functionalities serve as electron donors and facilitate the oxidation of the ferrocenyl group.[E75]
144 Appendix
1 Appendix D (Chapter C)
G. Filipczyk, S. W. Lehrich, A. Hildebrandt, T. Rüffer, D. Schaarschmidt, M. Korb, H. Lang, Eur. J. Inorg. Chem., 2017, 263–275.
Multiferrocenyl Cobalt-Based Sandwich Compounds
Grzegorz Filipczyk,[a] Steve W. Lehrich,[a] Alexander Hildebrandt,[a] Tobias Ruffer,[a] Dieter Schaarschmidt,[a] Marcus Korb,[a] and Heinrich Lang*[a]
Dedicated to Professor Dr. Max Herberhold on the occasion of his 80th birthday
[a] Technische Universität Chemnitz, Fakultät für Naturwissenschaften, Institut für Chemie, Anorganische Chemie, 09107 Chemnitz, Germany, E-mail: [email protected] chemnitz.de, https://www.tu-chemnitz.de/chemie/anorg/
Abstract
5 5 5 The reaction of FcC≡C–C≡CFc (Fc = Fe(η -C5H4)(η -C5H5)) (1) with Co(η -C5H5)(CO)2 (2) afforded ferrocenyl-functionalized cyclobutadiene and cyclopentadienone cobalt(I) compounds as well as multiferrocenyl benzene derivatives. The synthesis procedures are described. Eleven products could be separated by column chromatography and were characterized by NMR, UV/Vis and IR spectroscopy, high resolution ESI-TOF mass spectrometry and elemental analysis. For five representatives the structure in the solid state was determined by single X-ray structure analysis. The electronic properties of the
145 appropriate compounds were studied using cyclic and square-wave voltammetry. Further investigation of the interaction between FeII/FeIII centres in the mixed-valent species was achieved by in situ UV/Vis/NIR spectroelectrochemistry. These measurements demonstrated that weak electronic metal-metal interactions through the cobalt- coordinated cyclobutadiene building block occur (weakly coupled class II systems according to the classification of Robin and Day), while the cyclopentadienone core acts as insulator (class I) and hence only electrostatic interactions are characteristic.
Acknowledgements
The authors are grateful to the Fonds der Chemischen Industrie (FCI) for financial support. D. S. and M. K. thank the FCI for PhD fellowships.
2 Appendix E (Chapter D)
G. Filipczyk, A. Hildebrandt, U. Pfaff, M. Korb, T. Rüffer, H. Lang, Eur. J. Inorg. Chem. 2014, 4258–4262.
Combining Cobalt-assisted Alkyne Cyclotrimerization and Ring Formation via C–H Bond Activation – An “One-Pot” Approach to Complex Multimetallic Structures
Grzegorz Filipczyk,[a] Alexander Hildebrandt,[a] Ulrike Pfaff,[a] Marcus Korb,[a] Tobias Rüffer,[a] and Heinrich Lang*[a]
[a] Technische Universität Chemnitz, Fakultät für Naturwissenschaften, Institut für Chemie, Anorganische Chemie, 09107 Chemnitz, Germany, E-mail: [email protected] chemnitz.de, https://www.tu-chemnitz.de/chemie/anorg/
146 Abstract
Multiferrocenyl-substituted benzenes could be obtained in a “one-pot” reaction of 1,4- diferrocenyl butadiyne with substoichiometric amounts of [CpCo(CO)2] combining cobalt- assisted formal [2+2+2] cycloaddition with C–H bond activation at a single catalyst. A mechanism for the reaction is discussed. The newly synthesized hexaferrocenyl species belongs to the rather scarcely examined family of multimetallic aromatic compounds. It is one of the few examples in which the ferrocenyl units are either single bonded or 1,2- substituted to give rise to planar chirality at three of the ferrocenyl units. Electrochemical studies showed that up to six consecutive ferrocenyl-based redox events are observed. Within in situ spectro-electrochemical measurements of both compounds it is shown that two intervalence charge-transfer pathways are possible. At different excitation energies either a charge transfer through the peripheric ethylene bridging unit or through the central benzene unit occurs.
Acknowledgements
We are grateful to the Fonds der Chemischen Industrie (FCI) for financial support. M.K. thanks the FCI for a fellowship.
3 Appendix F (Chapter E)
G. Filipczyk, A. Hildebrandt, T. Rüffer, M. Korb, H. Lang, J. Organomet. Chem., 2017, 142– 151.
147 C C PPh2 Fe
C ) 9 o 2 O (C (C O e 2 ) F 8 (CO)3 Co C C PPh 2 C C PPh2 Fe Fe(CO)4 Fe Co (CO)3
C o ) 9 2 (C O O (C ) e 2 8 F (CO)3 Co
C C PPh2 Fe Co Fe(CO)4 (CO)3
Coordination Behavior of (Ferrocenylethynyl)diphenylphosphane Towards Binuclear Iron and Cobalt Carbonyls
Grzegorz Filipczyk, Alexander Hildebrandt, Tobias Rüffer, Marcus Korb and Heinrich Lang*
Technische Universität Chemnitz, Faculty of Natural Sciences, Department of Chemistry, Inorganic Chemistry, D-09107 Chemnitz (Germany) *) Corresponding author. Email: [email protected]; Phone: +49 (0)371- 531-21210; Fax.: +49 (0)371-531-21219.
Abstract
5 5 The reaction of PPh2(C≡CFc) (Fc = Fe(η -C5H4)(η -C5H5)) (1) with Fe2(CO)9 (2) and
Co2(CO)8 (3) afforded Fe(CO)4(PPh2(C≡CFc)) (4), Fe(CO)3(PPh2(C≡CFc))2 (5),
2 2 Fe2(CO)6(µ,η -C≡CFc)(µ-PPh2) (6) (reaction of 1 with 2), PPh2((η -C≡CFc)Co2(CO)6) (7)
2 and Co2(CO)7(PPh2((η -C≡CFc)Co2(CO)6)) (8) (reaction of 1 with 3). Treatment of 4 with
2 one equiv of 3 produced Fe(CO)4(PPh2((η -C≡CFc)Co2(CO)6)) (9). This compound was also obtained when 7 was reacted with 2. All compounds were characterized by NMR, UV/Vis and IR spectroscopy, high resolution ESI-TOF mass-spectrometry and elemental analysis. The structures of 4 and 6–8 in the solid state were determined by single crystal
X-ray structure analysis. These studies verified that 1 acts as a κP-ligand to a Fe(CO)4
fragment in 4. In 7 and 8 the C≡C unit is µ-κC:κC’ coordinated to a Co2(CO)6 fragment, and
additionally for 8 the PPh2 unit is datively-bonded to a Co2(CO)7 moiety. By the reaction of 1 with 2 at elevated temperature, the P–C bond in 1 is cleaved and hence 6 is formed in
2 which the Ph2P unit is µ-1:2κ P coordinated and the FcC≡C moiety is bonded in a µ-
148 2 1 2 1:2κ C ,κC fashion to a Fe2(CO)6 (Fe–Fe) entity. The electronic properties of 4–6 and 9 were studied by cyclic and square-wave voltammetry. The replacement of a CO ligand in 4
nd with a 2 PPh2(C≡CFc) ligand induces electrochemical reversibility of the Fe(CO)3 moiety in 5. As compared to non-coordinated 1, a cathodic shift of the Fc redox potentials is characteristic for 6 and 9, respectively, whereas an anodic shift is observed for 4 and 5.
Acknowledgements
We are grateful to the Fonds der Chemischen Industrie for financial support. M. K. thanks the Fonds der Chemischen Industrie for a PhD fellowship.
149 Curriculum Vitae
Personal data Date of birth: 07.01.1966 Place: Chorzow (Poland) Marital situation: Single
Academic Training in Chemistry: Diploma Chemical Technical High School, Chorzow, Poland 1981-1986 Major: Technology of Chemical Processes Master of Science University of Silesia, Katowice, Poland 1987-1992 (Chemistry) Major: Chemistry Dissertation: Polarograpic method of analysis of sulfur- containing pesticides Certificate Certified teachers license University of Silesia, Katowice, Poland 1992 PhD Candidate University of Pittsburgh, Pittsburgh, USA 2003-2007 Major: Inorganic, Bioinorganic and Bioanalytical Chemistry Project: Development of polymetallic luminescent lanthanide reporters. Comprehensive examination passed in December 2005 Master of Science degree in Chemistry received from the University of Pittsburgh, USA in August 2006 Left the University of Pittsburgh in August 2007. PhD Technische Universität Chemnitz, Deutschland 2010-2017
Combined Studies of Philosophy and Theology: Certificate Faculty of Philosophy and Theology (Society of the 1992-1994 Divine Word), Nysa, Poland Major: Philosophy and Theology (continued in Sankt Augustin, Germany) Diploma of Faculty of Philosophy and Theology (Society of the 1995-1998 Theology Divine Word), Sankt Augustin, Germany
Teaching experience as a Teaching Assistant (University of Pittsburgh, USA) from 2003 to 2007: General Chemistry Laboratory, three semesters, General Chemistry Recitation, three semesters, Inorganic Laboratory preparation, one semester, Organic Chemistry Recitation and Laboratory, one semester (May-July 2007), Accomplishment of the workshop: Computational Chemistry for Chemistry Educators, Completed Computational Chemistry Project for Teaching Organic Chemistry: http://chemed.chem.pitt.edu/cacc/minicourse/index.htm
150 Work on Computational Chemistry Project for Teaching General Chemistry (May-June 2007), Tutoring undergraduate students in using computer programs for learning chemistry and solving chemical problems, Organizing and Proctoring of the Pittsburgh Chemistry Olympics, Mentoring, training and supervision of undergraduate research.
Teaching experience as a Lecturer (San Carlos University, Cebu, Philippines) from 2007 to 2010: Employed as a Lecturer with a rank of an Assistant Instructor at the Department of Chemistry, University of San Carlos from November 1, 2007. Promoted to the rank of Full Instructor on October 1, 2009. I have been teaching the following courses:
General and Inorganic Chemistry Lectures, Chem 4 General and Inorganic Chemistry Lectures, Chem 14 General and Inorganic Chemistry Laboratory, Chem 4L Organic Chemistry Lecture for Chemical Engineering, Chem 30 Organic Chemistry Lecture for Chemical Engineering, Chem 31 Inorganic Chemistry Lecture for BS Chem, Chem 101 Advanced Inorganic Chemistry Laboratory for BS Chem, Chem 105L Advanced Inorganic Chemistry Lecture for Graduate School, Chem 201 Quantum Chemistry Lecture for BS Chem, Chem 153 Advanced Instrumental Analysis Lecture for Graduate School, Chem Development of new teaching subject (completed) - Computational Chemistry: Molecular Modeling - Syllabus, Computer Lab Manual, Instructors Manual, Report Sheets, April 2009
151 Publications
1. Lanthanide Complexes with More Intense Luminescence: A Strategy for the Formation of Polymetallic Lanthanide Dendrimer Complexes and Semiconductor Nanocrystal Compounds, D. A. Chengelis, A. M. Yingling, G. P. Filipczyk and S. Petoud, Proc.SPIE. 2006, 6370, 6300Y-01-6300Y-11.
2. Combining Cobalt-Assisted Alkyne Cyclotrimerization and Ring Formation through C–H Bond Activation: A “One-Pot” Approach to Complex Multimetallic Structures, G. Filipczyk, A. Hildebrandt, U. Pfaff, M. Korb, T. Rüffer, H. Lang, Eur. J. Inorg. Chem. 2014, 4258–4262
3. 1,3,5-Triferrocenyl-2,4,6-tris(ethynylferrocenyl)-benzene – a new member of the family of multiferrocenyl-functionalized cyclic systems, U. Pfaff, G. Filipczyk, A. Hildebrandt, M. Korb, H. Lang, Dalton Trans. 2014, 43, 16310–16321
4. Coordination behavior of(ferrocenylethynyl)diphenylphosphane towards binuclear iron and cobalt carbonyls, G. Filipczyk, A. Hildebrandt, T. Rüffer, M. Korb, H. Lang, J. Organomet. Chem., 2017, 142–151.
5. Multiferrocenyl Cobalt-Based Sandwich Compounds, G. Filipczyk, S. W. Lehrich, A. Hildebrandt, T. Rüffer, D. Schaarschmidt, M. Korb, H. Lang, Eur. J. Inorg. Chem., 2017, 263–275.
Oral Presentations:
1. Polymetallic Dendrimer-naphthalimide Lanthanide Complexes as Luminescent Oxygen Sensors in Living Cell.
Graduate/Post-Doc Research Seminar on Bioanalytical sensors preceding the Gordon Research Conference, Ventura, CA, USA, February 2006. (http://www.grc.org/programs.aspx?year=2006&program=gradsens)
2. Polymetallic Luminescent Dendrimer-Lanthanide Complexes and their application in bioimaging.
Seminar for Science Department, University of San Carlos, Talamban, Cebu, Philippines, February 2008.
Poster Presentations:
1. Polymetallic Dendrimer-naphthalimide Lanthanide Complexes as Luminescent Oxygen Sensors in Living Cell.
Gordon Research Conference on Bioanalytical Sensors, Ventura, CA, USA, February 2006.
152 2. Lanthanide complexes with more intense luminescence: A strategy for the formation of polymetallic lanthanide dendrimer complexes.
Asia-Pacific Conference on Chemical Education and 24th Philippine Chemistry Congress, Tagbilaran City, Bohol, Philippines, April 2009.
153 Acknowledgements
I offer my deepest gratitude to my supervisor Prof. Dr. Heinrich Lang for giving me the opportunity to join his research group as well as for his constant guidance, encouragement, his patience, enthusiasm, and immense knowledge. For the past several years he has helped me to develop my background in chemistry in a good environment and a good ambiance. Without him I would not have been able to finish my dissertation. I thank Dr. T. Rüffer, Dr. D. Schaarschmidt and Dr. Marcus Korb for the X-ray structure analysis and the helpful discussions. I am grateful to Dr. R. Buschbeck for the ESI-Mass analysis and to Ms. Ute Stöß and Ms. Janine Fritzsch for carrying out elemental analysis. I would like to thank Dr. Holm Petzold for discussion of NMR results. I would like to thank my colleagues for the many prove readings and helpful discussions. In this regards I would like to say thank you particularly to Dr. A Hildebrandt, Steve Lehrich, Dr. Dominique Miesel, Dr. D. Schaarschmidt, Dr. A Jakob, Dr. D. Adner, Dr. Bianka Milde, Dr. M. Abdulmalic, Dr. P. Djomgoue, A. Khalladi, Dr. Marcus Korb and Dr. U. Pfaff Many thanks also to Dr. R. Buschbeck and Br. Martin Azzopardi M. Sc. for English checking. I shall not forget to thank my family, dear friends and confreres for all your supports during this difficult period of my life.
154 Selbstständigkeitserklärung
Hiermit erkläre ich an Eides statt, dass ich die vorliegende Promotionsarbeit mit dem Titel „Ferrocenyl-Alkynides: Reaction Behavior towards Cobalt and Iron Carbonyl Compounds“ selbstständig und ohne unzulässige Hilfsmittel angefertigt habe. Alle wissentlich verwendeten Textausschnitte, Zitate oder Inhalte anderer Verfasser wurden ausdrücklich als solche gekennzeichnet. Die Arbeit hat in dieser oder ähnlicher Form noch keiner anderen Prüfungsbehörde vorgelegen.
Chemnitz, den 31.05.2017
______
Grzegorz P. Filipczyk
155