摘要:
Rhenium hydrido carbyne complexes Re(equivalent to CCH=CCMe3)C equivalent to CR)HCl(PMe2Ph)(3) (R = H, n-pentyl) PR 1 undergo 1,2-hydrogen shift reactions from the metal to the carbyne carbon atom to give complexes Re(HCCHC(CMe3)CCR)HCl(PMe2Ph)(3), which have two isomeric forms, namely, a metallabicyclo[3.1.0]hexatriene complex, in which the chloride is cis to the metal-bonded CH, and an alkyne-carbene complex, in which the chloride is trans to the metalbonded CH. In contrast, a similar transformation does not occur for the analogous complex Re(equivalent to CCH=C(CMe3)C equivalent to CSiMe3)HCl(PMe2Ph)(3), which has a SiMe, group on the C equivalent to C moiety. A computational study suggests that the difference in the reactivity of the hydrido carbyne complexes is related to steric effects in the corresponding hydride-shift products. Formation of Re(HCCHC(CMe3)CCSiMe3)HCl(PMe2Ph)(3) is not favored, mainly due to the steric interactions of the SiMe3 group with CMe3 and one of the phosphine ligands in the resulting metallabicyclo[3.1.0]hexatriene complex, and of the Siivle, group with the chloride ligand in the resulting allcyne-carbene complex.