Metal carbonyl chemistry. Part XXVI. Preparation, spectroscopic properties, and mode of decomposition of some halogenoethylene complexes of tetracarbonyliron, and the reaction of nonacarbonyldi-iron with lodotrifluoroethylene

Abstract

Nonacarbonyldi-iron reacts under very mild conditions with a range of halogenoethylenes to give complexes of the form [(olefin)Fe(CO)₄][olefin = CH₂:CHF, CH₂:CF₂, CHF:CF₂, CHBr:CF₂, CHCl:CF₂, CF₃·CF:CF·CF₃, CF₃·CH:CH·CF₃(CF₃)₂C:C(CF₃)₂, CCl₂:CCl₂, etc.]. Thermal decomposition gives the original olefin and pentacarbonyliron; traces of the geometric isomer of the olefin {e.g. cis-CF₃·CH:CH·CF₃ from the complex [(trans-CF₃·CH:CH·CF₃)Fe(CO)₄]} may arise via an intermediate zwitterion in which rotation about the original double-bond is possible. The spectroscopic properties of the complexes are more in accord with the ‘ferracyclopropane’ model structure than the ‘complexed olefin’ structure.

Trifluoroiodoethylene reacts anomalously with nonacarbonyldi-iron to give a dimer [{(C₂F₃I)Fe(CO)₄}₂], of unknown structure, and a low yield of tetracarbonyliodo(trifluorovinyl)iron.