Cyclic Carbene Ligand Research Articles

Highly E- and Z-Selective Hydrogenation of Alkynes Using Chromium and Cyclic Carbene Ligands

Highly E- and Z-Selective Hydrogenation of Alkynes Using Chromium and Cyclic Carbene Ligands

Divalent Nitrogen(I) Compounds with a New Cyclic Carbene Ligand

Divalent Nitrogen(I) Compounds with a New Cyclic Carbene Ligand

CARBENE LIGANDS DIVERSIFIED

A NEW FAMILY OF CYCLIC carbene ligands has been synthesized, expanding the arsenal of these popular ligands and opening a door to homogeneous catalysis of a broader range of chemical reactions. cyclic alkyl-amino carbenes (CAACs) were prepared by Vincent Lavallo, Guy Bertrand, and their coworkers at the University of California, Riverside ( Angew. Chem. Int. Ed. , published online Aug. 1, dx.doi.org/10.1002/ anie.200501841). CAACs are five-membered rings with a nitrogen atom adjacent to the carbene carbon on one side and a quaternary carbon atom adjacent to the carbene on the opposite side. The design of this new class of ligand is quite interesting since, for the past 10 years, the field of carbene ligands has been dominated by cyclic diamino ligands, also known as N-heterocyclic carbenes [NHCs], observes Cathleen M. Crudden of Queen's University, Kingston, Ontario. The advantages of the new ligands are their very strong electron-donating power, their facile synthesis, and the fact that ...

A comparison of some complexes of the type eq-[Mn 2(CO) 9L], where L is a cyclic carbene ligand with a five- or six-membered ring and the molecular structures of two complexes containing six-membered carbene rings

Two new five-membered ring cyclic carbene complexes eq-[Mn 2(CO) 9L] (where L= CCH 2CH(CH 3)CH 2O or CC(CH 3) 2CH 2CH 2O ) have been prepared and characterized. Thermal analysis and 1H/ 2D exchange experiments are compared for several five- and six-membered ring cyclic carbene complexes of the type eq-[Mn 2(CO) 9L]. The X-ray crystal structures of the six-membered ring carbene complexes eq-[Mn 2(CO) 9L] (where L= CCH 2CH 2CH 2CH 2O and CCH 2CH 2CH 2CH(CH 3)O ) have been determined and are compared with the known structures of the related five-membered ring complexes.

Synthesis of dimanganese nonacarbonyl cyclic carbene complexes and molecular structures of two of them

The reactions of Br(CH 2 ) 3 Br, BrCH 2 CH 2 CH(C-H 3 )Br, Br(CH 2 ) 4 Br, and BrCH 2 CH 2 CH 2 CH(CH 3 )Br with Na-[Mn(CO) 5 ] yield the dimanganese cyclic carbene complexes [(CO) 5 MnMn(CO) 4 L] (where L=CCH 2 CH 2 CH 2 O, CCH 2 CH 2 CH(CH 3 )O, CCH 2 CH 2 CH 2 CH 2 O, and CCH 2 CH 2 CH 2 CH(CH 3 )O, respectively). The structures of the first two of these complexes have been determined by X-ray crystallography, and this confirms that the cyclic carbene ligand occupies an equatorial position. IR, 1 H and 13 C NMR, and mass spectra are reported and discussed for these carbene complexes

Pseudohalogeno-Metallverbindungen, LXVIII [1]. Reaktionen der Cyanometallsäuren NCAuCNH, (NC)4Pt(CNH)2, (NC)2M(CNH)4(M = Fe, Ru, Os) und Co[bis(dimethyIglyoximato)](CN)CNHmit Epoxiden: 2-Hydroxyalkylisocyanid- und Oxazolidin-2-yIiden-MetalIkomplexe / Pseudohalogeno Metal Compounds, LXVIII [1]. Reaction of Cyano Metal Acids NCAuCNH, (NC)4Pt(CNH)2, (NC)2M(CNH)4 (M = Fe, Ru, Os) and Co[bis(dimethylglyoximato)](CN)CNH with Epoxides: 2-Hydroxyalkylisocyanide and Oxazolidine-2-ylidene Metal Complexes

NCAuCNH reacts with expoxides to give oxazolidine-2-ylidene (2) and 2-hydroxyalkyl complexes (3), respectively. Complexes with cyclic carbene ligands [XXX] (5) and [XXX] (7) are formed from the corresponding isocyanic metal compounds and oxiranes. 5b has been characterized by crystal structure determination. Ring opening of phenyloxirane occurs at the phenyl substituted carbon atom. (NC)2M(CNH)4 (M = Fe, Ru, Os) and oxirane yield mixtures of [XXX] and [XXX].

Syntheses and reactions of acyclic and cyclic carbene complexes cis-[MI(CMeNHMe)(CO)2(η-C5H5)](M = Mo or W) and cis-[MI{C(CH2)nNMe}(CO)2(η-C5H5)](M = Mo, n= 3 or 4; M = W, n= 3) obtained through alkyl migration to methyl isocyanide co-ordinated to molybdenum or tungsten. X-Ray structure of cis-[MoI{C(CH2)3NMe}(CO)2(η-C5H5)

Reaction of the isonitrile anion [M(CNMe)(CO)2(η-C5H5)]–(M = Mo or W) with I(CH2)3I in tetrahydrofuran solution results in good yields of the carbene complexes cis-[MI{[graphic omitted]Me}(CO)2(η-C5H5)]. The structure of the molybdenum compound was studied by X-ray crystallography. It crystallises as red needles, triclinic, a= 7.824(3), b= 13.363(6), c= 14.559(6)A, α= 78.62(4), β= 77.37(3), and γ= 80.99(4)°; R converged to 0.0385 for 2 378 independent reflections. There are two essentially similar independent molecules within the asymmetric unit. The cyclic carbene ligand and the iodine atom are mutually cis. The carbene ligand adopts a reverse orientation relative to the cyclopentadienyl ring in that the NMe substituent is orientated below the basal plane away from the cyclopentadienyl ring in contrast to the O substituent in related oxacyclopentylidene complexes. The molecule fails to interconvert from the observed cis configuration to the expected trans complex. An important feature of the formation of this molecule is a facile migration reaction of the alkyl chain to an isonitrile ligand. The six-membered carbene ring complex cis-[Mol{[graphic omitted]Me}(CO)2(η-C5H5)] is formed in the analogous reaction of [Mo(CNMe)(CO)2(η-C5H5)]– with I(CH2)4I. Both molybdenum carbene complexes react with Li(BEt3H) by attack at the carbene affording [[graphic omitted]Me}(CO)2(η-C5H5)](n= 3 or 4). Treatment of these complexes with acid results in the evolution of the organic heterocycle N-methylpyrrolidine (n= 3) or N-methylpiperidine (n= 4). The acyclic carbene compounds cis-[MI(CMeNHMe)(CO)2(η-C5H5)](= Mo or W) are formed in high yield in the reaction of the corresponding anion [M(CNMe)(CO)2(η-C5H5)]– with MeI followed by MeCO2H and LiI.

Reactions of metallabromoalkanes [M{(CH2)nBr}(CO)3(η-C5H5)](M = Mo or W, n= 3 or 4) with transition metal anions. Dimetalla-alkane and cyclic carbene complex formation. Crystal and molecular structures of [(η-C5H5)(OC)3Mo{(CH2)4}Mo(CO)3(η-C5H5)] and [(η-C5H5)(OC)3MoW(CO)2{C–O–(CH2)2CH2}(η-C5H5)

Reaction of Br[CH2]3Br with excess [Mo(CO)3(η-C5H5)]– leads to the spectroscopically characterised [(η-C5H5)(OC)3MoMo(CO)2{[graphic omitted]H2}(η-C5H5)] containing a cyclic carbene ligand. This species is formed via the intermediate [Mo{(CH2)3Br}(CO)3(η-C5H5)]. The related complex [(η-C5H5)(OC)3MoW(CO)2{[graphic omitted]H2}(η-C5H5)] is formed during reaction of [Mo{(CH2)3Br}(CO)3(η-C5H5)] with [W(CO)3(η-C5H5)]– and has been characterised by X-ray crystallography. This molecule crystallises as maroon needles, monoclinic, a= 8.017(6), b= 15.026(16), c= 7.981 (3)A, β= 92.88(5)°; R converged to 0.0645 for 1 256 independent reflections for which I/σ(I) > 3.0. The molecule contains a Mo–W single bond of 3.239(4)A, the cyclic carbene ligand is bonded to tungsten rather than molybdenum and is situated trans to the Mo–W bond regarding the co-ordination polyhedra of both metals as square-based pyramidal. Reaction of [M(CO)3(η-C5H5)]– with I[CH2]nI leads to [(η-C5H5)(OC)3M{(CH2)n}M(CO)3(η-C5H5)](M = Mo, n= 4; M = W, n= 3 or 4). The structure of one member of this class [(η-C5H5)(OC)3Mo{(CH2)4}Mo(CO)3(η-C5H5)] has been determined by X-ray crystallography. The molecule crystallises as yellow elongated plates, triclinic, a= 6.978 2(16), b= 7.005 1(10), c= 11.315 0(25)A, α= 102.378(15), β= 95.806(18), γ= 105.909(15)°; R converged to 0.0263 for 1 646 independent reflections. The molecule contains a crystallographically imposed centre of symmetry at the centre of the tetramethylene chain and the molecular structure may be compared to that of the known [(η-C5H5)(OC)2Fe{(CH2)4}Fe(CO)2-(ηC5H5)].

Synthese, Molekül-und Elektronenstruktur eines Radikal-Kationkomplexes [Cr(CO)4(Carben)2]+ / Synthesis, Molecular and Electronic Structure of a Radical Cationic Complex [Cr(CO)4(Carbene)2]+

Abstract A new one-step synthesis for bis-carbene complexes cis-M(CO)4L2 (M = Cr, Mo, W) containing cyclic carbene ligands L has been developed. These compounds can be oxidized by ferrocenium salts to paramagnetic cation complexes [M(CO)4L2]+ which, for M = Cr, are isolable in the form of their PF6 salts. The chromium compounds with L= 1,3-dimethyl-4-imidazolin-2-ylidene permit for the first time a structural and spectroscopic comparison of a diamagnetic carbene complex with the corresponding paramagnetic cation; the experimental facts are interpreted by molecular orbital calculations.

Cyclic carbene complexes of molybdenum and tungsten. Crystal and molecular structure of [Mol(CO)2{CO(CH2)2CH2}(η-C5H5)

The cyclic carbene complex [Mol(CO)2{[graphic omitted]H2}(η-C5H5)] is formed during reaction of [Mo(CO)3(η-C5H5)]– with I[CH2]3l or of [Mo{(CH2)3Br}(CO)3(η-C5H5)] with Lil. Crystals of this complex are Monoclinic, space group P21/c, with a= 6.372(2), b= 14.168(5), c= 14.390(3)A, β= 98.12(2)°, and Z= 4. The molecule contains mutually trans carbonyl ligands and a cyclic carbene ligand in which all but one of the ring carbon atoms are coplanar with the metal. Similarly, reactions of [Mo{(CH2)3Br}(CO)3(η-C5H5)] with SPh– or CN– provide [MoX(CO)2{[graphic omitted]H2}(η-C5H5)](X = SPh or CN). The cyclisation is tolerant to functionality on the cyclopentadienyl ring, thus reaction of [Mo(CO)3(η-C5H4R)]– with I[CH2]3l produces [Mol(CO)2{[graphic omitted]H2}(η-C5H4R)][R = Me, C(O)Me, or SiMe3]. The tungsten analogue [W{(CH2)3Br}(CO)3(η-C5H5)] undergoes carbene formations with l– and CN– to form [WX(CO)2{[graphic omitted]H2}(η-C5H5)](X = l or CN). Formation of the carbene complexes is likely to proceed by migration of the (CH2)3Br alkyl group to an adjacent CO group together with co-ordination of the incoming anion. This is followed by a ring closure reaction eliminating Br– and isomerisation so that in all cases the two CO groups are mutually trans in the isolated products. While [Mol(CO)2{[graphic omitted]H2}(η-C5H5)] does not react with transition-metal anions to form dinuclear carbene complexes by elimination of l–, the salt [Mo(CO)2(PPh3){[graphic omitted]H2}(η-C5H5)]Br reacts with [W(CO)3(η-C5H5)]– to give the unusual acyl complex [(η-C5H5)(Ph3P)(OC)2MoC(O)(CH2)3W(CO)3(η-C5H5)].

Studies on transition metal complexes with cyclic carbene ligands. 4. Electrochemical oxidation of dicarbene metal carbonyl complexes. Isomerization via an electrochemical reaction with no net current flow

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudies on transition metal complexes with cyclic carbene ligands. 4. Electrochemical oxidation of dicarbene metal carbonyl complexes. Isomerization via an electrochemical reaction with no net current flowReuben D. Rieke, Hiroyuki Kojima, and Karl OefeleCite this: J. Am. Chem. Soc. 1976, 98, 21, 6735–6737Publication Date (Print):October 1, 1976Publication History Published online1 May 2002Published inissue 1 October 1976https://doi.org/10.1021/ja00437a070RIGHTS & PERMISSIONSArticle Views179Altmetric-Citations61LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (355 KB) Get e-Alerts Get e-Alerts

Isomerisierungsreaktionen von cis- und trans-Dicarben-Komplexen des Typs M(CO)4L2 (M = Cr, Mo, W).

A series of bis-carbene complexes cis-M(CO)4L2 (M = Cr, Mo, W) containing cyclic carbene ligands (L= 1,2-dimethyl-4-pyrazoline-3-ylidene, 1,3-dimethyl-4-imidazoline-2-ylidene, 2,4-dimethyl-1,2,4-triazoline-3-ylidene and 1,3-dimethyl-benzimidazoline-2-ylidene) was prepared, and the photo-induced conversion to the corresponding trans-isomers was investigated. The trane-M(CO)4L2 complexes were characterized by their IR and 1H NMR spectra, and their irreversible thermal isomerisation to the thermodynamically more stable cis-isomers was studied both in solution and in the solid state.

The crystal and molecular structure of trans-[methyl- (2-oxacyclopentylidene)bis(dimethylphenylphosphine)- platinum(II)] hexafluorophosphate

The carbene complex trans-[CH 3( CH 2 COCH 2 CH 2 )Pt{P(CH 3) 2 C 6 H 5} 2]PF 6 crystallizes in the centrosymetric orthorhombic space group Pcca ( D 8 2h) with a = 15.503(7), b = 18.81(1), c = 17.66(1) Å. The measured density of 1.81(1) g cm −3 agrees with d(calc) = 1.81 g cm −3 for M = 703.41 and Z = 8. Three dimensional X-ray diffraction data were collected on an automatic four circle diffractometer using Mo radiation. The structure was solved by a combination of Patterson, Fourier and least-squares refinement techniques. The final conventional agreement factor for the converged model is R 1 = 0.044, calculated on 1763 observations for which I > 3σ( I), with 160 variables. The anion lies on a crystallographic two-fold axis of symmetry, and is disordered. The coordination geometry is essentially square planar about the platinum atom. The cyclic carbene ligand is almost planar and is coordinated approximately perpendicular to the Pt square plane. The mean PtP distance is 2.305(5), the PtC( sp 3) bond length is 2.080(18) and the C( sp 2) atom lies 2.00(2) Å away from the platinum atom. The structure is discussed in terms of the trans-influences of the ligands, and the character of the PtC( sp 2) bond.

The chemistry and structure of Chugaev's salt and related compounds containing a cyclic carbene ligand

Download options Please wait... Article information DOI https://doi.org/10.1039/J19710002097 Article type Paper Download Citation J. Chem. Soc. A, 1971, 2097-2104 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions The chemistry and structure of Chugaev's salt and related compounds containing a cyclic carbene ligand G. Rouschias and B. L. Shaw, J. Chem. Soc. A, 1971, 2097 DOI: 10.1039/J19710002097 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author G. Rouschias B. L. Shaw