Carbene Carbon Atom Research Articles

ChemInform Abstract: Bidentate Alkene‐Aminocarbene Complexes of Chromium. Synthesis and Reactivity Toward Alkynes.

AbstractIt is demonstrated that the coupled alkyne insertion double‐bond cyclopropanation reactions are general for complexes bearing the bidentate alkene‐aminocarbene ligands, provided that no phenyl group is present on the carbene carbon atom.

Zur Umpolung der Reaktivität eines Carbenkohlenstoffatoms – Unerwartete elektrophile Addition an einen η2‐Thiocarbenkomplex des Wolframs

On the Umpolung of the Reactivity of a Carben Atom – Unexpected Electrophilic Addition to an η‐Thiocarbene of TungstenTrifluoroacetic acid protonates the electrophilic carbene carbon atom of dicarbonyl(η5‐cyclopentadienyl) [η2‐methyl(methylthio)carbene]tungsten tetrafluoroborate (2) to provide the cationic tungsta‐thia‐cyclopropane complex 3. The 1H‐ and 13CNMR spectra of diastereomers 3a, 3b and the X‐ray structure of 3a are described.

Transformation of aziridinocarbene complexes of chromium and tungsten into nitrile complexes and olefins

Abstract Carbene complexes of chromium and of tungsten bearing the methylaziridine group on the carbene carbon atom undergo a thermal rearrangement with elimination of propene to give nitrile complexes of the metals.

Reactions of the metallacycle [(OC)(cp)FeC(SMe)SC(FeLn)S]+with nucleophiles. X-Ray crystal structures of the complexes [(OC)(cp)FeC(NC5H10)SC(FeLn)S]SO3CF3and [(OC)(cp)FeC{(CN)(SMe)}SC(FeLn)S][FeLn= Fe(cp)(CO)2, cp =η-C5H5

Reactions of the metallacyclic cation [(OC)(cp)[graphic omitted]]+[FeLn= Fe(cp)(CO)2, cp =η-C5H5] with nucleophilic agents have been investigated. The results indicate that the carbene carbon atom bonded to the endocyclic iron is the site of addition of all the nucleophiles examined. Primary amines NH2R (R = Me, C6H11, or Bun) form neutral isocyanide derivatives [(OC)(RNC)(cp)FeSC(S)FeLn] with opening of the FeC2S2 ring, whereas secondary amines such as NHR2(R = Me or Et) or H[graphic omitted]H2(n= 3 or 4) produce stable cationic cyclic aminothiocarbenes. The structure of one of these, [(OC)(cp)[graphic omitted]]SO3CF3, has been determined by X-ray diffraction [triclinic, a= 11.570(2), b= 12.242(2), c= 10.552(2)A, α= 104.60(2), β= 87.51(1), γ= 117.24(2)°, Z= 2, and space group P]. The cation contains the five-membered planar ring [graphic omitted] with the Fe(cp)(CO)2 and NC5H10 groups bonded to the carbon atoms. The C(carbene)–N interaction exhibits strong double-bond character [1.32(1)A], typical for an iminium cation. Methanethiol, Li(BHEt3), and KCN yield neutral [(OC)(cp)[graphic omitted]](X = SMe, H, or CN). In the hydride addition an isomeric mixture has been ascertained by i.r. and n.m.r. spectra, whereas the cyanide ion adds stereoselectively at the prochiral carbene centre to form only one diastereoisomer whose steric nature has been determined by X-ray diffraction [triclinic, a= 6.894(2), b= 10.057(1), c= 14.520(2)A, α= 96.00(2), β= 96.17(1), γ= 106.31(1)°, Z= 2, and space group P]. In this derivative the [graphic omitted] ring undergoes substantial changes because the iron-bonded carbon atom becomes four-co-ordinate with loss of its carbenic character and significant out-of-plane displacement. A comparative analysis of the relevant geometric features of all the members of this family is reported. Propane-1,3-dithiol produces the neutral spirocyclic [(OC)(cp)[graphic omitted]] which shows equivalence of the two diastereotopic SCH2 carbons in the high-temperature 13C n.m.r. spectrum and splitting of v(CO) in the i.r. spectrum. These spectroscopic features are discussed and interpreted.

Carbene-complex-promoted ring expansion of aziridine: formation of the 1-azabicyclo[4.3.0] ring system by a double alkyne and a single carbon monoxide insertion reaction

A chromium carbene complex (2) bearing a 2-methylaziridine ring system on the carbene carbon atom easily undergoes a double diphenylacetylene and a single CO insertion reaction to give a 1-oxotetrahydroindolizine derivative (4), which has been fully characterized by X-ray analysis of its Cr(CO)3 adduct (3).

Stereochemistry of chiral ruthenium- and iron-cyclopentadienyl alkylidenecarbene-diphosphine complexes

The non-rigid behaviour of complexes of the type [η-C 5H 5)M(Ph 2PCHRCHR′PPh2)(CCHR″)] PF 6 (M Ru or Fe; R,R′H, CH 3 or (CH 2) 3; R″ CH 3, C 6H 5 or tC 4H 9; not all combinations) has been investigated through 31P NMR spectroscopy at variable temperature. The preferred geometry of the complexes in solution is the one in which the plane of the alkylidenecarbene moiety is perpendicular to the plane containing the carbene carbon atom, the metal atom and the centroid of the cyclopentadienyl ligand, the barrier of rotation being 9–10 kcal/mol. When R ≠ R′, at least in the case of the ruthenium complexes, the stereogenic metal atom is sterically stable. For the complexes containing chiral diphosphine ligands, the two rotamers are in a diastereomeric relationship. The differences in the population of the two diastereomers (asymmetric induction) seem to be mostly determined by steric reasons. They increase on going from ruthenium to iron, by increasing the size of the alkylidene group on the carbene atom and by using diphosphines which cause a larger crowding around the metal. Furthermore for the complexes having a stereogenic metal atom, the asymmetric induction also depends on the absolute configuration at the metal (the chiral ligand being the same).

Tetracarbonyl(carbene-phosphine) and tetracarbonyl(imidate-phospine) complexes of chromium(0)

Treatment of the carbene complexes [(CO) 5Cr{C(OEt)CH 2PPh 2}] (I) with LiBu followed by alkylation with [Et 3O[BF 4] gives the carbene-phosphine chelates [(CO) 4 Cr{C(OEt)C(OEt)(Bu)CH 2P Ph 2}] (IV) and [(CO) 4Cr{C(OEt)C(OEt)=CHPPh 2}] (V). The tungsten analogs cannot be prepared similarly. With the substituted hydrazine, MeNHNH 2 at −80°C, NH addition to the carbene carbon atoms in the precursor complexes and concomitant ligand rearrangement produces the pentacarbonylphosphine compounds [(CO) 5M{PPh 2CH 2C(OEt)=NH}] (VIII, IX; M = Cr, W). The heterometallocyclic carbene-phosphine compounds react by formal NH insertion into the metalcarbene bond to give the six-membered chelates [(CO) 4 Cr{NH=C(OEt)C(OEt)(Bu)CH 2P Ph 2}] (X) and [(CO) 4 Cr{NH=C(OEt)C-(OEt)=CHP Ph 2}] (XI). The complex [(CO) 4 Cr{C(NH 2)C(OEt)=CHP Ph 2}] (VI), obtained by aminolysis of [(CO) 4Cr {C(OEt)C(OEt)=CHP Ph 2}] (V), has been the subject of a single crystal X-ray diffraction study. It crystallizes in the monoclinic space group P2 1 c with a 12.55(1), b 13.50(1), c 12.83(1) Å, β 90.2(1)°, V 2174 Å 3 and D(cald) 1.37 g cm−3 for mol.wt. 447.37 and Z = 4. The structure was refined to R = 0.067 and R w = 0.050. The CrC(carbene) bond length is 2.037(5) Å and the CrP distance 2.352(1) Å.

Anthracene Derivatives as Acceptors of the Reaction Intermediate Generated by the Decomposition of Tropone Tosylhydrazone Sodium Salt. Regioselective Cycloaddition Reactions of Cycloheptatrienylidene or 1,2,4,6-Cycloheptatetraene with 9-Substituted Anthracene Derivatives

Abstract The rearrangement of the carbene, cycloheptatrienylidene, to the allene, 1,2,4,6-cycloheptatetraene, was investigated. Tropone tosylhydrazone sodium salt, the precursor of cycloheptatrienylidene was decomposed in the presence of various kinds of 9-substituted anthracene derivatives to afford cycloaddition products, whose structures show that the carbenic carbon atom or the allenic carbon atom of the carbene or the allene attacks the carbon atoms at the 10-position of the anthracenes. It is obvious that the electronic natures of the substituents on the anthracenes have no effect on the regioselectivity of the addition reaction, suggesting that the reaction proceeds via 1,2,4,6-cycloheptatetraene, which is derived from the cycloheptatrienylidene initially generated from the tosylhydrazone.

A fluorochlorocarbene complex of osmium, OsCl 2(CFCI)(CO)(PPh 3) 2 and the structure of a fluoroalkoxycarbene complex of ruthenium, RuCl 2(CFOCH 2CMe 3)(CO)(PPh 3) 2

OsCl 2(CFCl)(CO)(PPh 3) 2 results from reaction between OsCl 2(CCl 2)(CO)(PPh 3) 2 and Cd(CF 3) 2(DME). The CFCl ligand is converted into CFNMe 2 and CFSEt ligands through reaction with Me 2NH and NaSEt, respectively. The crystal structure of RuCl 2(CFOCH 2CMe 3)(CO)(PPh 3) 2 reveals the following dimensions about the carbene-carbon atom: Ru C, 1.914(5)Å; C O, 1.303(7)Å; C F, 1.307(6)Å; Ru C F, 127.1(4)°; Ru C O, 125.5(4)°; F C O, 107.4(5)°.

Cleavage of the carbon-silicon bonds in trimethylsilylacetylenes by trans[(PR 3) 2PtX(R′OH)]PF 6 cations and formation of cationic alkoxycarbene complexes of platinum(II)

Cationic alkoxycarbene complexes of platinum(II) have been isolated in the reactions of trans-[(PR 3) 2PtX(R′OH)]PF 6 (X  H or Me; R′  Me or Et) with Me 3SiCCR′′ (R′′  H, Me or SiMe 3). In these reactions cleavage of the carbon-silicon bond by the nucleophilic attack of alcohol has been observed. These carbene complexes have been characterized by elemental analyses and by IR, 1H and 13C NMR spectral data. 13C NMR chemical shift data for carbene carbon atoms suggest that the carbene carbon may be very positively charged.

Untersuchungen zur struktur und stereochemie der additionsprodukte von nukleophilen an von N-methylbenzimidchlorid abgeleitete carbenchelatkomplexe

In the reaction of [C 5H 5(CO) 2 MoC(C 6H 5)N(CH) 3C(C 6H 5)N (CH 3)]PF 6 (I) with C 6H 5MgBr the phenyl group adds to the carbene carbon atom giving the neutral complex C 5H 5(CO) 2 MoC(C 6H 5) 2 N(CH 3)C(CH 6H 5)N (CH 3) (V). V crystallizes in the space group P2 1/ c with the cell constants a 11.803(5), b 12.114(6), c 17.198(6) Å, β 96.61(3) 0, V 2431.2 Å 3, Z = 4, π ca;c 1.45 g cm −3. For 2979 reflections the R value is 5.1, R w = 4.8. The stereoisomers IIIA and IIIB, formed in the H − addition to I, are 1H NMR spectroscopically investigated by means of Nuclear-Overhauser-Effect Difference Spectroscopy in order to elucidate the orientation of the incoming H substituent with respect to the C 5H 5 group.

Strukturuntersuchungen an mono- und bis-alkoxy(triphenylsilyl)-carben-komplexen des rheniums

Steric and electronic influences on bond lengths and angles at the carbene carbon atoms of cis-Re 2(CO) 9C(OR)SiPh 3 (I: R = CH 3, II, R = C 2H 5) and cis, trans-Re 2(CO) 8[C(OEt)SiPh 3] 2 (III) are discussed based on their structural analyses. I (ReRe 305.2(1) pm; ReC(carbene) 209(2) pm) and II (two independent molecules; ReRe 305.0(3) and 305.2(4) pm; ReC (carbene) 208(5) and 210(5) pm) differ by the cis and trans positions of the alkyl groups at the partial C(carbene)O double bonds. The change in configuration affects the bond angles at the carbene carbon. In III the carbene ligands are bonded to different rhenium atoms; cis to one Re atom and trans to the other Re atom (ReRe bond 309.1(2) pm). The ReC(carbene length of the trans- carbene ligand is significantly shorter (185(3) pm) than that of the cis-carbene ligand (208(3) pm).

Neue aspekte der metallkohlenstoff-bindung in übergangsmetallcarben-komplexen: die kristall- und molekülstruktor von (π-benzol)-dicarbonyl-methoxyphenylcarben-chrom

π-Benzenedicarbonylmethoxyphenylcarbenechromium crystallizes in the monoclinic space group P2 1/ c ( a 1125.6(6), b 1491.7(9), c 1931(2) pm and β 119.94(5)°) with two independent molecules in the asymmetric unit ( Z  8). The distance between the chromium and the carbene carbon atoms are the shortest found so far (193 und 194 pm). The bonding concept of transition metal carbene complexes can be extended if one considers the three groups bound to the carbene carbon competing for its positive charge. Thus all bond lengths and all bond angles around the carbene carbond depend on the π-donor ability of all three substituents.

ChemInform Abstract: TRANSITION METAL‐CARBENE COMPLEXES. IL. NUCLEOPHILIC ADDITION OF TERT‐BUTYLISOCYANIDE TO THE CARBENE CARBON ATOM OF DICARBONYLCYCLOPENTADIENYLPHENYLCARBENEMANGANESE TETRACHLOROBORATE

Chemischer InformationsdienstVolume 10, Issue 28 Organoelement Compounds ChemInform Abstract: TRANSITION METAL-CARBENE COMPLEXES. IL. NUCLEOPHILIC ADDITION OF TERT-BUTYLISOCYANIDE TO THE CARBENE CARBON ATOM OF DICARBONYLCYCLOPENTADIENYLPHENYLCARBENEMANGANESE TETRACHLOROBORATE E. O. FISCHER, E. O. FISCHERSearch for more papers by this authorW. SCHAMBECK, W. SCHAMBECKSearch for more papers by this authorF. R. KREISSL, F. R. KREISSLSearch for more papers by this author E. O. FISCHER, E. O. FISCHERSearch for more papers by this authorW. SCHAMBECK, W. SCHAMBECKSearch for more papers by this authorF. R. KREISSL, F. R. KREISSLSearch for more papers by this author First published: July 10, 1979 https://doi.org/10.1002/chin.197928292Read 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume10, Issue28July 10, 1979 RelatedInformation

Kinetische und mechanistische untersuchungen von Übergangsmetall-komplex-reaktionen : III. Abhängigkeit des gleichgewichts der addition von tributylphosphan an pentacarbonyl(arylmethoxycarben)wolfram vom substituenten am ring

The reaction of pentacarbonyl(arylmethoxycarbene)tungsten, (CO) 5W[C(OCH 3( p-C 6H 4R)] [R = OCH 3 (a), CH 3 (b), H (c), Br (d), CF 3 (e)], with tributylphosphane at low temperatures results in a reversible addition of the phosphane to the carbene carbon atom. The addition—dissoziation equilibrium is not only dependent on the temperature but also to a strong degree on the nature of the substituent R. Δ G, Δ H and the equilibrium constant K increase in the series from R = OCH 3 to R = CF 3. With the exception of R = OCH 3 the substituents b to e form an isentropic class. For all substituents (a to e) a linear dependency from Jaffés σ-constants was observed for Δ H. Good linear correlation for the substituents b to e was also found for log K and σ as well as for log K and the CO-force constants k cis and k trans .

ChemInform Abstract: SELECTIVITY AND SPECIFICITY IN CHEMICAL REACTIONS OF CARBENE AND CARBYNE METAL COMPLEXES

AbstractReview: Bericht über einen Vortrag, der auf dem "26th International Congress of Pure and Applied Chemistry" in Tokyo v. 4.9.

Sulphur-containing metal complexes. Part 4. Preparation of fac-tri-substituted carbonyl complexes of chromium(0) and tungsten(0) containing a phosphine, phosphite, or isocyanide ligand in addition to a chelate ring with carbene carbon and sulphur donor atoms

The reaction of LiBu with pentacarbonyl(thioether) complexes of chromium and tungsten [M(CO)5S(CH2R2)R1], in the presence of or prior to the addition of a π-acid ligand L, followed by alkylation, produces a series of tri-substituted carbonyl complexes of the type fac-[[graphic omitted]R1)R2}]. A proposed mechanism involving a double consecutive carbonylation is substantiated by the formation of a cis-tetracarbonyl(amino-carbenethio)-chelate as a by-product during one of the reactions in which L = CNBut.

Selectivity and specificity in chemical reactions of carbene and carbyne metal complexes

Abstract

The effect of alkyl substitution on the thermodynamic stability and kinetic reactivity of α-anions of metal—carbene complexes

Alkyl substitution was found to have only small effects on the thermodynamic and kinetic acidity and on the reactivity of anions generated α to the carbene carbon atom in metal—carbene complexes. The thermodynamic acidities of (2-oxacyclopentylidene)pentacarbonylchromium(0), I, and of (5-methyl-2-oxacyclopentylidene)pentacarbonylchromium(0), II, were found to be nearly equal. The rate of the base catalyzed deuterium exchange of the less substituted complex I, is 1.57 times faster than that of II. The reactivity of the anions generated from the less substituted complex I is 2.6–5.2 times less than that of anions generated from II.

Structure and basicity of anions generated .alpha. to the carbene carbon atom of transition metal-carbene complexes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure and basicity of anions generated .alpha. to the carbene carbon atom of transition metal-carbene complexesCharles P. Casey and Ronald L. AndersonCite this: J. Am. Chem. Soc. 1974, 96, 4, 1230–1231Publication Date (Print):February 1, 1974Publication History Published online1 May 2002Published inissue 1 February 1974https://doi.org/10.1021/ja00811a050RIGHTS & PERMISSIONSArticle Views149Altmetric-Citations92LEARN 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 (255 KB) Get e-Alerts Get e-Alerts