Übergangsmetall‐Carben‐Komplexe, CVII. Synthese von Pentacarbonylalkylchromaten(—I) und ‐wolframaten(—I)

Abstract

Pentacarbonyl(methoxyphenylcarben)chrom(O) und -wolfram(O) reagieren mit Methyl-bnv.Phenyllithium bei tiefen Temperaturen zu Lithium-pentacarbonylalkylmetallaten( -I) 1-4. Die Umsetzung dieser Komplexe mit Bis(tripheny1phosphin)iminium-chlorid ergibt Bis(tripheny1phosphin)iminium-pentacarbonylchlorochromat(0) (5) bzw. Bis(tripheny1phosphi)iminium-akylpentacarbonylwolframatd -I) 6, 7. Die Konstitutionen der neuen Verbindungen werden durch spektroskopische Untersuchungen gesichert. Transition Metal Carbene Complexes, CVII') Synthesis of PentacnrbonyIalky1c~omat~-I) and -tungstates(--I) Pentacarbonyl(methoxyphenylcarbene)chromium(O)and -tungsten(O) react with methyl-as well as phenyllithium at low temperatures to give lithium pentacarbonylalkylmetalates(-I) 1-4. Treatment of these complexes with bis(tripheny1phosphie)iminium chloride yields bis(tripheny1phosphine)iminium pentacarbonylchlorochromate(0) (5) as well as bis(tripheny1phosphie)iminium alkylpentacarbonyltungstates( -I) 6,7. The structures of the new compounds are established by spectroscopic investigations.Aufgrund ihres ausgcpragten elektrophilen Charakters am Carbenkohlenstoffatom reagieren (Alkoxyary1carben)peptacarbonyLKomplexe von Chrom(0) und Wolfram(0)2) rasch mit Aminen, Thiolen, Selenolen und Phosphinen '). Nicht grundgtzlich anders envartet man das Reaktionsverhalten bei Umsetzungen mit Lithiumorganylen 4).So gelang bei der Reaktion von (CO)&rC(OCH3)C6H5 mit Phenyllithium 6ei Raumtemperatur die Isolierung von l,2-Dimethoxy-l,l,2,2-tetraphenylethan 5), was nit einer Addition des Nucleophils an das &arbso, Spaltung der Metall-Methylenkohlenstoff-Bindung und Dimerisierung des organischen Liganden zu erklaren ist. Folgerichtig konnte in einer ') CVI. ubergangsmetall-Carben-Komplexe, CVII 3843 ahnlichen Reaktion rnit anschlieDender Methanolat-Abspaltung mittels HCl Pentacarbonyl(diphenylcarben)wolfram(O) dargestellt werden 6). Durch schonende Behandlung der postulierten Additionsverbindungen Li[(CO),-MC(OCHJ(R)R] rnit SiOJPentan gelang die Synthese neuer, teilweise sehr empfindlicher Pentacarbonyl(diary1carben)-und Pentacarbonyl(n-olefin)-Komplexe von Chrom(0) und Wolfram(O)'_). Von diesen Ergebnissen ausgehend stellte sich nunmehr die Frage, ob eventuell diese intermediaren Metallate isolierbar sind. In diesem Fall lieDe sich dann der Reaktionsablauf unschwer beweisen. b, C. P . Casey und T J . Burkhardt. J. Am. Chem. SOC. 95,5833 (1973).

Chemistry of transition metal carbene complexes: nucleophilic substitution reactions of cyanamide anion to Fischer carbene complexes

“…Most synthetic applications of Fischer carbene complexes have involved common nucleophiles such as amines, 1,[3][4][5][6][7] hydrazine, 1,8 oximes, 1,9 alkoxide ions, 1,3,10 thiolate ions, 1,3,[11][12][13] carbanions, [13][14][15][16][17][18] or aryl and alkyl lithiums as well as others. 1,[19][20][21] In the early literature there have been only a few kinetic studies, focusing mainly on reactions with amines 3,[22][23][24] and phosphines 3,25,26 in weakly polar organic solvents.…”

Catalytic chemical transformations with conformationally dynamic catalytic systems

“…The catalytic function of chiral [CrCl] 2+ -salen in this allosteric system was evaluated in the catalytic ring-opening reaction of cyclohexene oxide (12) reported by Jacobsen et al (Scheme 2). 18 Upon addition of bis(triphenylphosphine)iminium chloride (PPNCl) followed by CO purge, 19 the closed catalyst 10 was transformed quantitatively into opened catalyst 11 and the reaction rate of 12 with TMSN 3 was doubled. 20 This closed/opened system, in which the opened state exhibits enhanced catalytic activity for a specific reaction, has a wide range of applications.…”

Transition metal carbene chemistry 5: Kinetic studies on the nucleophilic substitution reactions of (CO)5MC(SCH3)CH3 (M=Cr and W) with primary amines in aqueous acetonitrile

“…(1) involves the reactions of Fischer carbene complexes with amines, it includes a proton transfer as additional step compared to their reactions with anionic species like MeO À , RS À , carbanions, etc. Though in most synthetic applications common nucleophiles such as amines [1,[3][4][5][6][7], hydrazine [1,8] oximes [1,9], alkoxide ions [1,3,10] thiolate ions [1,3,[11][12][13], carbanions [13][14][15][16][17][18], (mainly aryl and alkyl lithium) as well as others [1,[19][20][21] were involved, there have been relatively few kinetic studies in the early literature. These investigations focused mainly on reactions with amines [3,[22][23][24] and phosphines [3,25,26] in non-polar organic solvents.…”