Silacyclopentadiene complexes of molybdenum, chromium, iron, ruthenium, cobalt, and rhodium

Abstract

The synthesis of a series of transition-metal derivatives of various substituted silacyclopentadienes is described. A number of stoicheiometries and modes of bonding of the silacyclopentadiene molecule are reported. Molybdenum hexacarbonyl forms the bis(diene) complex [Mo(C₄Ph₂H₂SiMe₂)₂(CO)₂], but the same ligand forms only an arene complex with chromium hexacarbonyl, [Cr(C₄Ph₂H₂SiMe₂)(CO)₃]. Both [Co₂(C₄Ph₂H₂SiMe₂)(CO)₆] and [Co₂(C₄Ph₂H₂SiMe₂)₂(CO)₄] have been observed but only the latter could be isolated. Rhodium complexes formulated as [{Rh(C₄Ph₂H₂SiMe₂)Cl}₂] and [{Rh(CO)₂Cl}₂(C₄Ph₂H₂SiMe₂)] are reported and the latter is believed to involve a bridging silacyclopentadiene group. 1-Hydrido-1 -methyl-2,3,4,5-tetraphanyl-1-silacyclopentadiene forms exclusively the endo-H form of [Fe(C₄Ph₄SiMeH)(CO)₃] on reaction with [Fe₃(CO)₁₂], but the same silacyclopentadiene and [Ru₃(CO)₁₂] form [{Ru(C₄Ph₄SiMe)(CO)₄}₂] containing a Si–Ru–Ru–Si sequence. η⁴-Diene-bonded silacyclopentadiene complexes of ruthenium, [Ru(C₄Ph₂H₂SiMe₂)(CO₃)] and [Ru(C₄Ph₄SiPhCl)(CO)₃], are also reported. Structural and spectroscopic characteristics of these complexes are reported and compared and contrasted with related species.