DOCSLIB.ORG

A Neutral “Aluminocene” Sandwich Complex: Η1‐ Versus Η5

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Neutral “Aluminocene” Sandwich Complex: Η1‐ Versus Η5 Angewandte Communications Chemie International Edition:DOI:10.1002/anie.201907749 Main-GroupComplexes German Edition:DOI:10.1002/ange.201907749 ANeutral“Aluminocene” SandwichComplex: h1-versus h5- CoordinationModes of aPentaarylborole with ECp* (E = Al, Ga; Cp* = C5Me5) Christian P. Sindlinger* and Paul Niklas Ruth F Abstract: The pentaaryl borole (Ph*C)4BXyl [Ph* = 3,5- complexes,inparticular, is that borolediide salts act as F tBu2(C6H3); Xyl = 3,5-(CF3)2(C6H3)] reacts with low-valent reducing agents rather than as aligand source in metathesis Group 13 precursors AlCp* and GaCp* by two divergent reactions with p-block halides. routes.Inthe case of [AlCp*]4,the borole reacts as an oxidising We recently reported the synthesis of aset of novel, highly agent and accepts two electrons.Structural, spectroscopic,and soluble tert-butyl-decorated pentaphenyl boroles (Ph*C)4BR [12] computational analysis of the resulting unprecedented neutral [Ph* = 3,5-tBu2(C6H3)]. We are interested in further 5 5 F III h -Cp*,h -[(Ph*C)4BXyl ]complex of Al revealed astrong, expanding the chemical scope of boroles as ligands to the p- ionic bonding interaction. The formation of the heteroleptic block elements.Tocircumvent salt metathesis reactions,we F borole-cyclopentadienyl “aluminocene” leads to significant treated borole (Ph*C)4BXyl (A)with the established, changes in the 13CNMR chemical shifts within the borole unit. potentially reductive monovalent Group 13 reagents F In the case of the less-reductive GaCp*, borole (Ph*C)4BXyl (AlCp*)4 and GaCp* (Scheme 1). reacts as aLewis acid to form adynamic adduct with adative 2-center-2-electron Ga Bbond. The Lewis adduct was also À studied structurally,spectroscopically,and computationally. Fifty years ago,Eisch reported the first authentic isolation of pentaphenyl borole.[1] Free boroles are weakly anti-aromatic cyclic 4p-electron compounds.[2] Among avariety of intrigu- ing reactivities,including the activation of hydrogen[3] or Si H À bonds,[4] Diels–Alder reactions,and ring expansions,[1b, 5] boroles can be readily reduced by two electrons to form Hückel-aromatic borolediides[6] or they can react as potent Lewis acids.[7] In recent years,variation of the boron-bound substituent allowed for an extension of the library of known Scheme 1. Divergentreaction pathways of free borole A with AlCp* [2b, 6b,8] boroles with substantially altered optical gaps. and GaCp*. Thecoordination chemistry of boroles toward transition metals has been studied since the late 1970s.[6a,9] However, despite the isoelectronic nature of borolediide with the—in When GaCp* was added to borole A an immediate colour organometallic chemistry—ubiquitous and iconic cyclopenta- change from dark green to bright orange was observed. NMR dienyl anion, very few complexes other than with d-block spectroscopic examination of the reaction mixture confirmed metals or very electron-positive s-block metals are known. aclean conversion and the formation of asingle product. The Recently Müller, Albers,and co-workers reported aGeII- 1HNMR spectrum revealed no substantial changes in the borole complex that resulted from arearrangement during shifts compared to the individual starting materials.However, the reaction of agermole dianion with amidoborane diha- the 11BNMR signal drastically shifts from abroad signal in [10] lides. Although only afew comments are found in the the typical range of tricoordinate boron atoms at d11B = [9d, 11] literature, alikely reason for the scarcity of p-block 71 ppm (w1/2 = ca. 3250 Hz) in A to anarrower signal at d11B = 7.6 ppm (w1/2 = ca. 1550 Hz) in 2.The shift to higher [*] Dr.C.P.Sindlinger,M.Sc. P. N. Ruth field is aclear indication of ahigher coordination number at Institut fürAnorganische Chemie the boron atom.[13] Major changes ( 2ppm) in the Æ Georg-August-UniversitätGçttingen 13C{1H} NMR spectrum of the borole framework are observed Tammannstrasse 4, 37077 Gçttingen (Germany) for the a-and b-carbon atoms of the C4Bcycle as well as the E-mail:[email protected] ipso-and para-positions of the boron-bound aryl moiety Supportinginformation (including Experimental Details) and the (Table 1). ORCID identification number for one of the authors of this article can An interaction of the GaCp* fragment with the boron- be found under:https://doi.org/10.1002/anie.201907749. centred LUMO is also in line with the change in colour from 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. an intense green (stemming from p/p*excitation in free KGaA. This is an open access article under the terms of the Creative Commons AttributionLicense, which permits use, distribution and boroles) to abright orange.The colour of 2 is unique among I reproduction in any medium, provided the original work is properly the otherwise colorless (Cp/R)Ga adducts with Lewis-acidic cited. boranes.[13,14] Angew.Chem. Int.Ed. 2019, 58,15051 –15056 2019 The Authors. Published by Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim 15051 Angewandte Communications Chemie Table 1: Diagnostic NMR chemical shifts in C6D6 at 298 KofA, 1,and 2. B1-Ga1 92.60(11)8.The Ga Bbond (2.1382(19) )issimilar Calculated averaged values in brackets. À to those in B(C6F5)3 adducts of GaCp derivatives (2.154(3), [b] [b] [b] [b] 11 [13a, 14b] Compound Cb Ca i-CXylF p-CXylF B 2.155(6), 2.161(2) ). Thebond lengths within the [a] borole ring clearly reveal isolated C=Cand C Cbonds.The A 166.2 140.6 135.9 125.3 71.6 F À 1 128.4 118.0 144.2 119.1 24.6/17.3[c] Xyl residue at the tetracoordinate boron centre noticeably [126.1] [117.9] [144.8] [18.6] bends out of the borole plane away from the GaCp* cone.A 2 151.2 149.6 150.7 119.4 7.6/ 0.4[d] related structural motif and reactivity was also observed for À [151.7] [149.9] [151.6] [ 0.9] AlCp* adducts of 9-borafluorenes.[11] À [a] See Ref. [12].[b] 13CNMR shift in ppm in C D .[c] At 758Cin Over the course of afew weeks,small amounts of afine 6 6 À toluene. [d] At 508Cintoluene. grey solid deposited from solutions of 2 along with the À formation of unassigned decomposition products.[15] Clearly,the monovalent GaICp* was too reluctant to At ambient temperature,nofurther signal for free GaCp* transfer electrons and reduce the borole.Wetherefore turned I was observed after addition of afurther 0.5 equiv of GaCp* to to (AlCp*)4,asAl is astronger reductant. AlCp derivatives solutions of 2,thus indicating adynamic exchange of GaCp*. can also form base adducts with boranes.[16] Suspending the Variable-temperature NMR experiments of solutions of 2 in poorly soluble (AlCp*)4 in green solutions of A leads to avery toluene with aslight excess of GaCp* reveal hindered slow decolourisation over the course of three days to finally rotation of the C -bound Ph* groups starting at 408C. At yield pale yellow solutions.Monitoring the process by NMR b À 308C, the Cp* signal significantly broadens and gradual spectroscopy revealed avery clean conversion into asingle À cooling from 408Cto 758Cleads to two increasingly sharp product 1.Crystals of 1 readily form from concentrated À À separate Cp* signals of GaCp* and 2 being observed. The solutions in various hydrocarbons.Inall cases,and despite 1HNMR chemical shifts all lie in the range of pure GaCp*, numerous attempts,weobtained poorly resolved diffraction which is reported to likely form hexamers at low temper- data.[17] Examination of the data, however, allowed the key ature.[15] However,the intense orange colour does not change structural feature to be clearly identified:the anticipated 5 5 F III upon cooling,thus rendering apotential equilibrium between quasi h -Cp*,h -[(Ph*C)4BXyl ]Al sandwich complex 1. 2 and A + 1/6[GaCp*]6 unlikely.Orange-red crystals suitable This represents the first neutral “aluminocene” and the for X-ray diffraction grew from benzene solutions.The second borole complex of ap-block element.[10,18] Hetero- molecular structure clearly confirms the formation of leptic Cp/borole sandwich complexes are known for various aboron-centred Lewis-base adduct, with donation of the transition metals.[8e, 19] GaI lone pair of electrons into an empty porbital on boron Thequality of the data limits extensive structural dis- (Figure 1). TheGa1–Cp*centroid vector is virtually aligned with cussion;however, some key features can clearly be identified. the Ga1 B1 bond (175.58), and the Ga1–B1 vector is almost Compared to A and 2,which both feature localized cyclic 1,3- À perpendicular to the C4Bplane (C4-B1-Ga1 95.04(11)8,C1- butadiene systems,the atomic distances within the (C4B) ring in 1 are much more uniform. Shortened B C and C C À a bÀ b bonds together with an elongated C C bond are in line with aÀ b substantial p-delocalization, as expected for aHückel-aro- [6b] matic boroldiide. TheAl1-(C4B)centroid distance is approx- imately 1.80 ,which is slightly shorter than the Al1- Cp*centroid distance of approximately 1.86 .This is rational- ized by greater electrostatic attraction between the dianionic borole and AlIII compared to the simple monoanionic Cp*. TheCp* and borole units adopt adistorted staggered conformation. TheCp*-Al contacts range from 2.17(1) to 2.27(1) ,thus indicating aslight deviation of the Al atom from an ideal central localisation. Thedisorder in the X-ray structure prevents discussion of individual Al1 (C B) dis- À 4 tances.The DFT-optimised structure (Figure 2) reveals acen- tered Al atom with comparatively short Al C and Al B À a À contacts.All other experimental structural features are in general good agreement with the gas-phase DFT-optimised [20] Figure 1.
Load more

Recommended publications
  • A Germaaluminocene†
    Chemical Science View Article Online EDGE ARTICLE View Journal | View Issue A germaaluminocene† Cite this: Chem. Sci., 2020, 11, 2982 Lena Albers, * Patrik Tholen, Marc Schmidtmann and Thomas Muller¨ * All publication charges for this article The reactions of dipotassium germacyclopentadienediide with two Group 13 dichlorides, Cp*BCl and have been paid for by the Royal Society 2 * ff of Chemistry Cp AlCl2, yield two structurally di erent products. In the case of boron a borole complex of germanium(II) is obtained. The aluminium halide gives an unprecedented neutral Received 21st January 2020 Accepted 7th February 2020 germaaluminocene. Both compounds were fully characterised by multinuclear NMR spectroscopy supported by DFT computations. The molecular structure of the germaaluminocene was DOI: 10.1039/d0sc00401d determined by XRD. rsc.li/chemical-science Introduction conversion and aer work-up complex 2c was isolated as a brown oil in 35% yield (Scheme 2). NMR spectroscopy evi- The aim of utilizing readily available and environmentally denced the presence of the expected borole ring with a h1- benign main group element compounds for activation of bound cyclopentadienyl substituent. Interestingly, the NMR Creative Commons Attribution-NonCommercial 3.0 Unported Licence. unreactive materials and strong bonds instead of transition data indicated frozen rotation around the B-Ca single bond, metal-based complexes became increasingly popular during the giving rise to ten 13C NMR signals for the cyclopentadienyl last decade.1 We attempted to follow this lead by establishing substituent (Table S3, ESI†). In addition, all four carbon atoms polarised heteroalkenes I as they mimic the electronic situation of the borole ring are magnetically non-equivalent.
    [Show full text]
  • Parallels to Frustrated Lewis/Radical Pair Chemistry
    klh00 | ACSJCA | JCA11.2.5208/W Library-x64 | manuscript.3f (R5.0.i3:5004 | 2.1) 2020/02/05 13:43:00 | PROD-WS-121 | rq_481292 | 7/01/2020 12:12:45 | 10 | JCA-DEFAULT pubs.acs.org/IC Article 1 Redox-Controlled Reactivity at Boron: Parallels to Frustrated Lewis/ 2 Radical Pair Chemistry ⊥ ⊥ 3 Anthony Wong, Jiaxiang Chu, Guang Wu, Joshua Telser, Roman Dobrovetsky, and Gabriel Menard́ * Cite This: https://dx.doi.org/10.1021/acs.inorgchem.0c01464 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information 4 ABSTRACT: We report the synthesis of new Lewis-acidic boranes μ 5 tethered to redox-active vanadium centers, (Ph2N)3V( -N)B(C6F5)2 μ 6 (1a)and(N(CH2CH2N(C6F5))3)V( -N)B(C6F5)2 (1b). Redox IV/V 7 control of the V couple resulted in switchable borane versus 8 “hidden” boron radical reactivity, mimicking frustrated Lewis versus 9 frustrated radical pair (FLP/FRP) chemistry, respectively. Whereas V 10 heterolytic FLP-type addition reactions were observed with the V 11 complex (1b) in the presence of a bulky phosphine, homolytic peroxide, IV 12 or Sn−hydride, bond cleavage reactions were observed with the V * μ 13 complex, [CoCp2 ][(N(CH2CH2N(C6F5))3)V( -N)B(C6F5)2](3b), 14 indicative of boron radical anion character. The extent of radical 15 character was probed by spectroscopic and computational means. IV/V 16 Together, these results demonstrate that control of the V oxidation 17 states allows these compounds to access reactivity observed in both FLP 18 and FRP chemistry.
    [Show full text]
  • Pentamethylcyclopentadienyl Aminoborole Complexes of Hafnium
    Pentamethylcyclopentadienyl Aminoborole Complexes of Hafnium Thesis by Andrew F. Kiely In Partial Fufillment of the Requirements for the Degree of Doctor of Philosophy Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, California 1997 (Submitted August 20,1996) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. For M y Parents Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. iii Acknowledgments First and most importantly, I would like to thank John Bercaw for the support, encouragement, and opportunities that he has given me over the course of my studies at Caltech. I have been very fortunate to have been able to learn chemistry from someone who is a fine and generous person as well as a great scientist, and I am very grateful to him. I am also grateful to Bill Schaefer, Larry Henling, and Mike Day for performing all the crystallographic work that is reported in this thesis. I appreciate all their good humor and patience despite my (occasional) impatience and (more occasional) ignorance. I've really enjoyed hiking with Bill and playing outfield with Larry as well. The students and post-docs in the Bercaw group have been friends as well as coworkers. Over the years, people in the Bercaw group have been generous with their time, advice and friendship. When I was getting started in the group, Donny Cotter, Bryan Coughlin, and Roger Quan were never too busy to answer my questions or to set me straight. I'm especially grateful to Roger, who helped me to learn vacuum line techniques when I was starting on the aminoborole project.
    [Show full text]
  • The Water-Energy Nexus: Challenges and Opportunities Overview
    U.S. Department of Energy The Water-Energy Nexus: Challenges and Opportunities JUNE 2014 THIS PAGE INTENTIONALLY BLANK Table of Contents Foreword ................................................................................................................................................................... i Acknowledgements ............................................................................................................................................. iii Executive Summary.............................................................................................................................................. v Chapter 1. Introduction ...................................................................................................................................... 1 1.1 Background ................................................................................................................................................. 1 1.2 DOE’s Motivation and Role .................................................................................................................... 3 1.3 The DOE Approach ................................................................................................................................... 4 1.4 Opportunities ............................................................................................................................................. 4 References ..........................................................................................................................................................
    [Show full text]
  • Sulfur Bonded Unsymmetrical Borole Complexes: Synthetic, Spectroscopic and Biocidal Aspects
    SULFUR BONDED UNSYMMETRICAL BOROLE COMPLEXES: SYNTHETIC, SPECTROSCOPIC AND BIOCIDAL ASPECTS Taruna Pandey1, V. P. Singh2 and R. V. Singh1* 1 Department of Chemistry, University of Rajasthan, Jaipur-302004, India 2 DSME, S.C.E.R.T., Varun Marg, Defence Colony, New Delhi-110024, India ABSTRACT Synthesis, characterization and biological activities of some of the unsymmetrical borole complexes containing B-S and B<-N bonds are described. The sulfur containing conjugated bases were prepared by the condensation of caibonyl compounds with thiosemicarbazide. The resulting complexes have been characterized by elemental analysis, molecular weight determinations and spectral studies including IR, Ή NMR, "Β NMR and ,3C NMR. The spectroscopic results showed that the conjugated bases behave in a bidentate fashion, whereas, the complexes display a tetracoordinated environment around the boron atom as steriochemically active lone pair is also included in the coordinated sphere. The conjugated bases and their respective boron complexes have been screened for their antifungal and antibacterial properties. INTRODUCTION Recently, few references on bidentate ligands coordinated to boron through the azomethine nitrogen and the thiolo sulfur have been published in the literature1·2. These compounds are interesting in many respects. Some have got a number of applications in industry, biology and agriculture. Industrial applications of coordination compounds of boron have remained fairly limited. Boron analogues of carboxylic acids and peptides have been shown to possess interesting biological activities in particular as serine protease inhibitors3. Use of boron-nitrogen compound in neutron capture therapy of brain tumors have also been investigated4. Several organoboranes find promising applications in the synthesis of insect pheromones5.
    [Show full text]
  • SYNTHESIS, CHARACTERIZATION, in VITRO and in VIVO SCREENING of UNSYMMETRICAL BOROLE COMPLEXES of 2-HYDROXY-N-PHENYLBENZAMIDE and ITS DERIVATIVES Taruna Pandey and R
    SYNTHESIS, CHARACTERIZATION, IN VITRO AND IN VIVO SCREENING OF UNSYMMETRICAL BOROLE COMPLEXES OF 2-HYDROXY-N-PHENYLBENZAMIDE AND ITS DERIVATIVES Taruna Pandey and R. V. Singh* Department of Chemistry, University of Rajasthan, Jaipur 302004, India. ABSTRACT Biochemical aspects, synthesis and characterization of some boron complexes of 2-hydroxy-N- phenylbenzamide (HOPhBenz) and its semicarbazone (HOPhBenz.SCZH) and thiosemicarbazone (HOPhBenz.TSCZH) are described. These derivatives were prepared by the reactions of 2-isopropoxy-4- methyl- 1,3,2-dioxaborolane, and 2-isopropoxy-4-methyl- 1,3,2-dioxaborinane with 2-hydroxy-N-phenyl- benzamide, 1-[(2-hydroxyphenyl)-l-N-phenylamino]hydrazinecarboxamide (HOPhBenz.SCZH), and 1-[(2- hydroxyphenyl)-l-N-phenylamino]hydrazinecarbothioamide(HOPhBenz.YSCZH) in a 1:1 molar ratio. In order to assess the increase of the inhibitor potency, (HOPhBenz), (HOPhBenz.SCZH), (HOPhBenz. TSCZH) and their boron complexes have been tested in vitro against a number of pathogenic fungi and bacteria at different concentrations and were found to possess remarkable fungicidal and bactericidal properties. The testicular sperm density, testicular sperm morphology, sperm motility, density of cauda epididymal spermatozoa and fertility in mating trials and biochemical parameters of reproductive organs are discussed. INTRODUCTION Boron chemistry has continued to provide the most novel developments in the field of coordination chemistry. Inorganic chemistry of boron is much more diverse and complex than that of any other element in the Periodic Table and this is due to the elucidation of tremendous range of bondin intractions. Several organoboranes find promising applications in the synthesis of insect pheromones'. Boron azomethine complexes of various ligands have been found to possess conspicuous biocidal activity2.
    [Show full text]
  • Planar Chiral Lewis Acids and Lewis Pairs Based On
    PLANAR CHIRAL LEWIS ACIDS AND LEWIS PAIRS BASED ON FERROCENE by JIAWEI CHEN A Dissertation submitted to the Graduate School-Newark Rutgers, The State University of New Jersey in partial fulfillment of requirements for the degree of Doctor of Philosophy Graduate Program in Chemistry written under the guidance of Professor Frieder Jäkle and approved by Newark, New Jersey May, 2014 © 2014 Jiawei Chen ALL RIGHTS RESERVED ABSTRACT OF THE DISSERTATION PLANAR CHIRAL LEWIS ACIDS AND LEWIS PAIRS BASED ON FERROCENE by Jiawei Chen Dissertation Advisor: Professor Frieder Jäkle Organoboranes have been widely used for catalytic transformations, polymerizations, small molecule activation, anion and glycol sensing and construction of electronic materials. These remarkable applications commonly benefit from the electron-deficient nature of tricoordinate boron, i.e., its empty p- orbital can accommodate a lone pair of electrons or participate in conjugation of extended π-systems. Therefore, approaches to enhance the Lewis acidity of the boron center are desirable, and different strategies have been introduced with this aim, including (1) installation of electron withdrawing pendant groups such as pentafluorophenyl groups; (2) generation of cationic borenium species and (3) incorporation of tricoordinate boron into anti-aromatic systems such as borole derivatives. Recently, much effort has been directed to the preparation of the so- called “Frustrated Lewis Pair” (FLP) and the application of their unquenched relativity for catalytic transformations. However, chiral versions of highly Lewis acidic organoboranes remain scarce. On the other hand, planar chiral ferrocenes have proven to provide rigid frameworks for transition metal ligands such as ii phosphines and amines, which have been successfully applied to the asymmetric hydrogenation of alkenes, ketones and other processes.
    [Show full text]
  • A Computational Study on a Strategy for Isolating a Stable Cyclopentadienyl Cation
    DOI: 10.1002/chem.201xxxxxx █ Stabilized cyclopentadienyl cation A computational study on a strategy for isolating a stable cyclopentadienyl cation Kalon J. Iversen, David J. D. Wilson*[a] and Jason L. Dutton*[a] Abstract: A computational study has been carried out to derivative that may approach the stability of isolobal (and examine the feasibility of generating a simple monocyclic isolatable) borole rings, as evaluated by HOMO-LUMO and cyclopentadienyl cation that may be sufficiently stable to singlet-triplet gaps. These Cp+ derivatives may therefore be an isolate and handle at ambient temperatures. Using judicious attractive target for synthetic isolation. placement of electron withdrawing groups (CF3) about the ring we have identified a Introduction The isolobal neutral boron centred analogues (boroles) have recently experienced a resurgence of interest.[12] The + + [13] The antiaromatic cyclopentadienyl cation ([C5H5] ; [Cp] ; 1) has pentaphenyl borole ring (4) was reported some time ago, but long fascinated synthetic and theoretical chemists alike. The the determination of the solid state structure by Braunschweig in parent cation 1, has a triplet ground state and has been observed 2008 led to a substantial increase in activity.[14] Piers reported the at low temperatures via EPR studies, as have several substituted perfluorinated analogue (5) shortly thereafter.[15] These [1-3] analogues. However, as yet no isolatable monocyclic species compounds are indefinitely stable when stored under N2 or Ar and has been reported. The instability of the cation can be both species have demonstrated unusual and interesting [16-17] [18-22] rationalized from simple Hückel theory, where a 4- electron reactivity, such as H2 activation, reduction chemistry, triplet diradical is predicted (Figure 1).
    [Show full text]
  • 1 Full List of Publications – Prof. Holger Braunschweig 29.11.2019
    Full List of Publications – Prof. Holger Braunschweig 29.11.2019 2019 [560] Z.-F. Jiao, Y.-M. Tian, B. Zhang, C.-H. Hao, Y. Qiao, Y.-X. Wang, Y. Qin, U. Radius, H. Braunschweig, T. B. Marder, X.-N. Guo, X.-Y. Guo High Photocatalytic Activity of a NiO Nanodot-decorated Pd/SiC Catalyst for the Suzuki- Miyaura Cross-coupling of Aryl Bromides and Chlorides in Air submitted. [559] I. Krummenacher, J. K. Schuster, H. Braunschweig Synthesis and Reactivity of Bora- and Boratabenzenes in Patai’s Chemistry of Functional Groups (Eds. Ilan Marek and Mark Gandelman) 2019, DOI:10.1002/9780470682531.PAT0969 in press. [558] W. C. Ewing, T. Dellermann, Y. T. A. Wong, J. D. Mattock, A. Vargas, D. L. Bryce, H. Braunschweig Metal-free π-Complexes Between Diborynes and Main Group Atoms submitted. [557] F. Rauch, S. Fuchs, A. Friedrich, D. Sieh, I. Krummenacher, H. Braunschweig, M. Finze, T. B. Marder Having your cake and eating it too: highly stable, readily reducible, fluorescent, trifluoromethylated 9-borafluorenes submitted. [556] T. Thiess, M. Ernst, T. Kupfer,H. Braunschweig 1,4-Diaza-2,3-diborinines – Synthesis and Functionalization submitted. [555] D. Prieschl, G. Bélanger-Chabot, X. Guo, M. Dietz, M. Müller, I. Krummenacher, Z. Lin, H. Braunschweig Synthesis of Complex Boron-Nitrogen Heterocycles Comprising Borylated Triazenes and Tetrazenes Under Mild Conditions submitted. [554] G. Horrer, M. J. Krahfuß, K. Lubitz, I. Krummenacher, H. Braunschweig, U. Radius, N-Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbine Complexes of Titanium(IV) and Titanium(III) submited. [553] J. H. Muessig, P. Lisinetskaya, R. D. Dewhurst, R.
    [Show full text]
  • Unsymmetrical Borole Complexes of Monobasic Bidentate Benzothiazolines
    UNSYMMETRICAL BOROLE COMPLEXES OF MONOBASIC BIDENTATE BENZOTHIAZOLINES Taruna Pandey and R. V. Singh* Department of Chemistry, University of Rajasthan, Jaipur - 302004, India ABSTRACT The synthetic spectroscopic and biological studies of some unsymmetrical borole complexes derived from heterocyclic ketones and 2-mercaptoaniline have been characterized on the basis of elemental analysis molecular weight determinations and spectral studies including IR, !H NMR, 13C NMR and nB NMR. The equimolar reaction between unsymmetrical borole and these benzothiazolines have produced [B(C3H<;02) (N^S)] and [B^HgO^ (N°S)] type of boron complexes. The spectroscopic results show that the benzothiazolines behave in a monobasic bidentate fashion rendering the non-metal tetracoordinated. The benzothiazolines and their respective non-metal complexes have been screened for their antifungal and antibacterial properties. INTRODUCTION Boron and its compounds have attracted the attention of a large number of chemists mainly because of the tremendous range of structural peculiarities and subtle types of bonding. Boron shows an astonishing number of structural polymorphs. Further, the synthetic flexibility of boron, which has a wide range of 'applications in various disciplines, has attracted a number of investigators in the field. Arene boronic acids show antiserotonin activity1. The toxicity to mice of a number of triarylboranes and their amine complexes has been investigated2. Recently, interest has also been sustained in the structural aspects of compounds containing boron - nitrogen bonds3"7. Benzothiazolines, which are biologically very active, constitute an important class of nitrogen and sulphur donor ligands8"9. The inherent biological potential of sulphur donor ligands prompted us to prepare unsymmetrical borole complexes of benzothiazolines.
    [Show full text]
  • Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)
    NOMENCLATURE OF INORGANIC CHEMISTRY IUPAC Recommendations 2005 IUPAC Periodic Table of the Elements 118 1 2 21314151617 H He 3 4 5 6 7 8 9 10 Li Be B C N O F Ne 11 12 13 14 15 16 17 18 3456 78910 11 12 Na Mg Al Si P S Cl Ar 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 55 56 * 57− 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba lanthanoids Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 87 88 ‡ 89− 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 Fr Ra actinoids Rf Db Sg Bh Hs Mt Ds Rg Uub Uut Uuq Uup Uuh Uus Uuo * 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu ‡ 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr International Union of Pure and Applied Chemistry Nomenclature of Inorganic Chemistry IUPAC RECOMMENDATIONS 2005 Issued by the Division of Chemical Nomenclature and Structure Representation in collaboration with the Division of Inorganic Chemistry Prepared for publication by Neil G.
    [Show full text]
  • Advanced 1,1-Carboboration Reactions with Pentafluorophenylboranes
    Chemical Science PERSPECTIVE View Article Online View Journal | View Issue Advanced 1,1-carboboration reactions with pentafluorophenylboranes Cite this: Chem. Sci.,2016,7,56 Gerald Kehr and Gerhard Erker The 1,1 carboboration reaction of a variety of metal-substituted alkynes with simple trialkylboranes R3Byields the respective alkenylboranes (Wrackmeyer reaction). The use of the strongly electrophilic R-B(C6F5)2 reagents allows for much milder reaction conditions and gives good yields of the respective bulky alkenylboranes from conventional terminal alkynes by means of 1,2-hydride migration. Even internal alkynes undergo 1,1-carboboration with the R-B(C6F5)2 reagents, in this case yielding alkenylboranes by means of C–C bond cleavage. Phosphorus, sulfur or even boron containing substituents can serve as the migrating alkynyl substituents in the advanced 1,1-carboboration reactions using the R-B(C6F5)2 reagents. Sequential 1,1-carboboration of geminal bis(alkynyl) derivatives of these elements with the R-B(C6F5)2 Received 1st September 2015 boranes yields boryl substituted phospholes, thiophenes or even boroles in quite a variety. Vicinal Accepted 7th October 2015 bis(alkynyl)arenes or heteroarene substrates undergo benzannulation reactions in this way. Many of the Creative Commons Attribution 3.0 Unported Licence. DOI: 10.1039/c5sc03282b -B(C6F5)2 substituted 1,1-carboboration products can be used as reagents in cross coupling reactions. A www.rsc.org/chemicalscience recently disclosed organometallic analogue, namely a 1,1-carbozirconation reaction is described. Introduction: the Wrackmeyer reaction unusual alkenylboranes 2, that were formed by a reaction pathway involving 1,2-alkyl migration from the borate boron 1 In the mid-1960s Binger and Koster¨ described the reaction of atom to the acetylenic a-carbon atom (see Scheme 1).
    [Show full text]