Zur reaktion von metall-koordiniertem kohlenmonoxid mit yliden : VII. Trimethylphosphoranylidenmethyl(trimethylsiloxy)carben-komplexe von chrom,molybdän und wolfram: aufbau einer metallvinyl-einheit durch c(carbanion)c(carben)-π-wechselwirkung und photochemische e/z-isomerisierung

The treatment of the hexacarbonylmetal compounds M(CO)₆ (M = Cr. Mo, W) with two equivalents Me₃PCH₂ yields the phosphonium acylmetalphosphorus ylides Me₄P(CO)₅MC(O)CHPMe₃] 1a–1c. Their reaction with Me₃SiOSO₂CF₃ leads via O-silylation to formation of the neutral “siloxy(ylidecarbene) complexes” (CO)₅MC(OSiMe₃)CHPMe₃2a–2c, which are protonated by HX (X = Cl, CF₃SO₃) to give the thermolabile carbene complexes (CO)₅MC(OSiMe₃)H₂CPMe₃]X, 3a, 3b. ¹H, ¹³C NMR and IR data suggest, that delocalization of the ylidic charge to the carbene carbon generates a metal-coordinated vinyl group in the case of 2a–2c. In addition this fact is proved by the X-ray analysis of 2c, for which a C(ylide)C(carbene) bond distance of 133 pm is found. 2a–2c are obtained as pure E-isomers but can be converted to the Z-isomers 2a′–2c′ upon photolysis.