Metal Carbon Double Bond Research Articles

Heisenberg model for radical reactions. Part 3. Direct exchange coupling between transition metal ions and triplet methylene

Ab initio UHF calculations have been carried out for naked transition metal-methylene ions. The low-spin open-shell states are found to be the ground states of these ions, in accord with the GVB-CI results. The low-spin transition metal-methylene ions are regarded as direct exchange-coupled systems formed from high-spin transition metal ions and the triplet monocentric diradical. The direct exchange couplings between these species can be described on the basis of the Heisenberg model. The CASSCF calculations using UHF natural orbitals (UNOs) have been carried out for low-spin states, showing that UNOs and their occupation numbers are good trials. However, they provide poor binding energies for the transition metal-carbon double bonds and indicate the necessity for dynamical correlation corrections. The approximate spin-projected UHF Møller-Plesset and UHF coupled-cluster methods provide reasonable binding energies for the transition metal-methylene ions, which are close to those of modified coupled-pair functional (CPF) and average CPF methods.

Investigation of the dithiocarbamate-induced coupling of allylidene and carbonyl ligands on a tungsten center

Reaction of the allylidene tungsten complex [W(CPhCHCHMe)Br 2(CO) 2(4-picoline)] ( 1) with the dithiocarbamates MS 2CNR 2 ( a: M=Na, R=Et; b: M=Na, R=Me; c: M=Li, R=Ph) in THF at 50 °C affords the vinylketene tungsten complexes [W(S 2CNR 2) 2(OCCPhCHCHMe)(CO)] ( 2a–c). At lower temperatures, four reaction intermediates ( 3–6) may be discerned. Spectroscopic studies indicate that these compounds contain η 4-allyldithiocarbamate ligands which are generated by addition of dithiocarbamate across the metal-carbon double bond of the allylidene-tungsten unit in 1. The structures of [W(S 2CNEt 2) 2(OCCPhCHCHMe)(CO)] ( 2a) and of one intermediate, [W(η 4-Et 2NCS 2CPhCHCHMe)(S 2CNEt 2)(CO) 2] ( 5a) were elucidated by X-ray crystallography.

Zur Cycloaddition von Azidoameisensäuremethylester an die Metall-Carben-Doppelbindung in η2-Thiocarbenkomplexen des Molybdäns und Wolframs / Cycloaddition of Azidoformic Acid Methylester to the Metal Carbon Double Bond of η2-Thiocarbene Complexes of Molybdenum and Tungsten

Cationic η2-thiocarbene complexes of molybdenum and tungsten [Cp(CO)PMe3 [BF4] (R = Me, Ph, Tol) add N3COOMe to the electron rich metal carbon double bond to yield the corresponding bicyclic system. The products have been characterized by 1H, 13C, 31P NMR, IR and mass spectra. The crystal structure of 4b has been determined: space group P21/n with a = 1749.9(7), b = 827.9(1), c = 1846.8(7) pm and Z = 4.

Synthesis and structure of the unligated carbene of chromium

Complexes with metal-carbon double bonds have found applications as intermediates in many important catalytic reactions including cyclopropanation of alkenes by diazoalkanes, Fischer-Tropsch synthesis, olefin metathesis, Ziegler-Natta polymerization, alkane activation, and in the decomposition of transition metal alkyl complexes. However, complexes with the simplest carbene, CH[sub 2], coordinated to the metal center are relatively rare. In this paper the authors report the synthesis and characterization of the simple unligated carbene of chromium by FTIR matrix isolation spectroscopy. 7 refs., 3 figs., 4 tabs.

2-Methyl-4-alkenyl-2,3-dihydrofurans by cleavage of the metal–carbon double bond in α,β-unsaturated 2-oxacyclopentylidene pentacarbonyl chromium complexes

The reaction between the complex (CO)5CrC[graphic omitted] 1 and aliphatic aldehydes bearing α-H atoms, in the presence of dimethylamine hydrochloride and potassium carbonate, leads directly to 1,3-dienes 3a-f; in one case the formation of the intermediate 5 can be demonstrated.

ChemInform Abstract: Formation of Carbon‐Carbon Double Bonds by Novel Insertion Reactions of Allenes, Heterocumulenes and Acid Amides into Metal‐Carbon Double Bond of Fischer Carbene Complexes

ChemInformVolume 21, Issue 11 Reviews ChemInform Abstract: Formation of Carbon-Carbon Double Bonds by Novel Insertion Reactions of Allenes, Heterocumulenes and Acid Amides into Metal-Carbon Double Bond of Fischer Carbene Complexes R. AUMANN, R. AUMANN Org. Chem. Inst., Univ. Muenster, D-4400 MuensterSearch for more papers by this author R. AUMANN, R. AUMANN Org. Chem. Inst., Univ. Muenster, D-4400 MuensterSearch for more papers by this author First published: March 13, 1990 https://doi.org/10.1002/chin.199011368Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue11March 13, 1990 RelatedInformation

Intrinsic transition metal-carbon double bond dissociation energies: periodic trends in M+-CH2 bond strengths

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntrinsic transition metal-carbon double bond dissociation energies: periodic trends in M+-CH2 bond strengthsP. B. Armentrout, L. S. Sunderlin, and Ellen R. FisherCite this: Inorg. Chem. 1989, 28, 25, 4436–4437Publication Date (Print):December 1, 1989Publication History Published online1 May 2002Published inissue 1 December 1989https://doi.org/10.1021/ic00324a004RIGHTS & PERMISSIONSArticle Views155Altmetric-Citations48LEARN 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 (273 KB) Get e-Alerts Get e-Alerts

The influence of silyl groups on the reactivity and formation of metal-carbon double bonds

In the first part of the article the chemistry of silyl-substituted Fischer-type carbene complexes is reviewed. The presence of a silyl substituent at the carbene carbon considerably changes the properties of complexes of the type (CO) 5MC(XR)SiR′ 3 (M  Cr, Mo, W). Depending on the group XR, fragmentation of the carbene ligand (XR  OR or NHR), formation of stable 16-electron carbene complexes (CO) 4MC(NR 2)SiR 3, or formation of ketenes Ph 3Si(RX)CCO (X  O, S) is observed. In the second part two novel methods for the formation of metal-carbon double bonds are discussed, both involving elimination of R 3SiCl: in the first method anionic silyl complexes are used as equivalents of dianionic complexes in the reaction with geminal dihalides, in the second 1-chloro-1-trimethylsilylalkenes are brought into reaction with unsaturated metal fragments.

ChemInform Abstract: CATALYSIS BY TRANSITION METALS: METAL‐CARBON DOUBLE AND TRIPLE BONDS

Several well-characterized transition metal catalysts contain a metal-carbon double bond or a metal-carbon triple bond. In other homogeneous (or heterogeneous) catalyst systems in which the metal is likely to be in a relatively high oxidation state, such as molybdenum(VI) or tungsten(VI), metal-carbon multiple bonds may play an important role. Some recent results suggest that even supposedly well understood reactions such as ethylene polymerization may actually involve catalysts that behave as if they contained a metal-carbon double bond instead of a metal-carbon single bond. The chemistry of metal-carbon double and triple bonds should eventually complement and perhaps. overlap the known chemistry of complexes containing metal-oxygen double bonds or metal-nitrogen triple bonds, respectively; unique catalytic reactions involving carbon, nitrogen, and oxygen ligands multiply bonded to transition metals are therefore possible.

Catalysis by Transition Metals: Metal-Carbon Double and Triple Bonds

Several well-characterized transition metal catalysts contain a metal-carbon double bond or a metal-carbon triple bond. In other homogeneous (or heterogeneous) catalyst systems in which the metal is likely to be in a relatively high oxidation state, such as molybdenum(VI) or tungsten(VI), metal-carbon multiple bonds may play an important role. Some recent results suggest that even supposedly well understood reactions such as ethylene polymerization may actually involve catalysts that behave as if they contained a metal-carbon double bond instead of a metal-carbon single bond. The chemistry of metal-carbon double and triple bonds should eventually complement and perhaps. overlap the known chemistry of complexes containing metal-oxygen double bonds or metal-nitrogen triple bonds, respectively; unique catalytic reactions involving carbon, nitrogen, and oxygen ligands multiply bonded to transition metals are therefore possible.

Oxidation state control of the reactivity of a transition metal–carbon double bond. Synthesis, X-ray crystal structure, and reactions of the zerovalent difluorocarbene complex [Ru(CF2)(CO)2(PPh3)2

Reaction of [Ru(CO)2(PPh3)3] with [Cd(CF3)2(MeOCH2CH2OMe)] produces the zerovalent CF2-complex, [Ru(CF2)(CO)2(PPh3)2]; X-ray crystal structure determination reveals very distorted trigonal bipyramidal geometry and an RuC distance of 1.83(1)A, and reaction indicate that when compared with an RuII CF2-complex, the CF2-ligand in the zerovalent compound has greatly reduced reactivity towards nucleophiles and in fact reacts with the electrophiles HCL and Ag+ giving [Ru(CF2H)Cl(CO)2(PPh3)2] and [[graphic omitted]{H2O})(CO)2(PPh3)2]+, respectively.