Preparation and reactions of tricarbonyl(3-trimethylstannylcycloheptadienyl)iron hexafluorophosphate and tricarbonyl(3-trimethylsilylcycloheptadienyl)iron hexafluorophosphate

Abstract

The preparation of tricarbonyl(2-trimethylstannylcycloheptadiene)iron and tricarbonyl(2-trimethylsilylcycloheptadiene)iron is described. Hydride abstraction from these complexes, using triphenylmethyl hexafluorophosphate, leads to tricarbonyl(3-trimethyl-stannyl- and -silyl-cycloheptadienyl)iron complexes. Reaction of the trimethylstannyl-substituted dienyl complex with enolate nucleophiles gives the expected addition products, together with almost equal amounts of diene-Fe(CO) 3 complexes resulting from a nucleophile addition/protiodestannylation reaction. The trimethylsilylcycloheptadienyl complex is better behaved, giving good yields of nucleophile addition products. Cyanide anion adds to this complex to give exclusively the C(1) addition product, in contrast to tricarbonylcycloheptadienyliron cation, which gives mixtures of C(1) and C(2) addition products. Treatment of tricarbonyl(5-methyl-3-trimethylsilylcyclohepta-1,3-diene)iron with triphenylmethyl hexafluorophosphate resulted in loss of a methyl group to give tricarbonyl(3-trimethylsilylcycloheptadienyl)iron hexafluorophosphate, a highly unusual reaction.