The preparation and characterisation of monomeric and linked metal carbonyl clusters containing the closo-Si2Co4 pseudo-octahedral core

Abstract

PhSiH3 reacts with [Co4(CO)12] at 50 °C in hydrocarbon solvents to give [(μ4-SiPh)2Co4(CO)11], 2c, shown by an X-ray crystal structure determination to have a pseudo-octahedral Si2Co4 core. Substituted aryl-silanes behaved similarly. Mixtures of PhSiH3, H3SiC6H4SiH3 and [Co4(CO)12] in a ca. 2 ∶ 1 ∶ 2 ratio gave the dimeric cluster [{Co4(μ4-SiPh)(CO)11Si}2C6H4], 3a, which has the two Si2Co4 cores linked by a C6H4 group to give a rigid molecule which an X-ray structure analysis shows to be over 23 A long. Related dimers linked by –(CH2)8– groups were isolated from mixtures of PhSiH3, α,ω-(H3Si)2(CH2)8 and [Co4(CO)12]. Electrochemical studies show the two cluster units in 3a do not interact electronically.