Ethenyl and ethynyl derivatives of Tricarbonyl(η-cyclobutadiene)iron

Abstract

Tricarbonyl(1-4-η-ethenylcyclobutadiene)iron and a number of its derivatives (3a-d) have been prepared in good yield from tricarbonyl(η- cyclobutadienecarbaldehyde)iron (2) by reaction with methylenetriphenylphosphoranes. Reaction of (E)- and (Z)- tricarbonyl[methyl 2-bromo-3-(η-cyclobutadienyl)propenoate]iron, (3b) and (3c), with potassium t-butoxide gave tricarbonyl[methyl 3- (η- cyclobutadienyl)propynoate]iron (4a) in low yield. Attempts to prepare tricarbonyl(1-4-η-ethynyl-cyclobutadiene)iron (4b) by debromination of tricarbonyl[1-4-η-(2?,2?-dibromoethenyl)cyclobuta-diene]iron(3d) were unsuccessful.