Metal-Mediated Allyl Transfers in (Alkynylallylsilane)Co2(CO)6 Complexes: A Synthetic and Structural Study

The alkyne complex (CH2CHCH2SiMe2C⋮CCMe2OH)Co2(CO)6, 5, is a potential precursor to either a metal-stabilized silylium or carbenium species. Treatment with HBF4 initially produces the cobalt-stabilized carbocation, which undergoes fluoride-promoted allyl migration to give (FSiMe2C⋮CCMe2CH2CHCH2)Co2(CO)6, 8. Fe(CO)5 reacts with 5 to yield the “dehydroxylated” iron−cobalt cluster (CH2CHCH2SiMe2CCCMe2)FeCo(CO)6, 13, which upon addition of HBF4 loses propene to give the corresponding fluorosilane cluster (FSiMe2CCCMe2)FeCo(CO)6, 14. This latter molecule has been characterized by X-ray crystallography and may be regarded as an excellent structural model for the analogous cationic dicobalt cluster.