METAL-MEDIATED ALLYL TRANSFERS IN (ALKYNYLALLYLSILANE)CO-2(CO)(6) COMPLEXES - A SYNTHETIC AND STRUCTURAL STUDY

The alkyne complex (CH2=CHCH2SiMe2C=CCMe2OH)Co-2( CO)(6), 5, is a pote ntial precursor to either a metal-stabilized silylium or carbenium spe cies. Treatment with HBF4 initially produces the cobalt-stabilized car bocation, which undergoes fluoride-promoted allyl migration to give (F SiMe2C=CCMe2CH2CH=CH2)Co-2(CO)(6), 8. Fe(CO)(5) reacts with 5 to yield the ''dehydroxylated'' iron-cobalt cluster (CH2=CHCH2SiMe2C=C=CMe2)Fe Co(CO)(6), 13, which upon addition of HBF4 loses propene to give the c orresponding fluorosilane cluster (FSiMe2C=C=CMe2)FeCo(CO)(6), 14. Thi s latter molecule has been characterized by X-ray crystallography and may be, regarded as an excellent structural model for the analogous ca tionic dicobalt cluster.