An investigation of the reaction between [{Fe(η5–C5H5)(CO)2}2] and aryl isonitriles

Abstract

The direct reaction between [{Fe(η⁵-C₅H₄X)(CO)₂}₂](X = H, Me, or COOMe) and aryl isonitriles RNC (R = 2,6-Me₂C₆H₃ or C₆H₅) in refluxing toluene readily yields the tetrasubstituted derivatives [{Fe(η⁵-C₅H₄X)(RNC)₂}₂]. The intermediate derivatives [Fe₂(η⁵-C₅H₅)₂(CO)_4–n(RNC)_n](n= 1 or 2) can be prepared by the exchange reaction between [{Fe(η⁵-C₅H₅)(RNC)₂}₂] and [{Fe(η⁵-C₅H₅)(CO)₂}₂]. Reaction rates for the substitution of [{Fe(η⁵= C₅H₅X)(CO)₂}₂] by RNC are dependent on both the nature of R and X, and increase with both the nucleophilicity of R and the electron-withdrawing power of X. An alternative route to [Fe₂(η⁵-C₅H₅)₂(CO)_4–n(RNC)_n](n= 1 or 2) is via the reaction between Na[Fe(η⁵-C₅H₅)(CO)₂] and 2,6-Me₂C₆H₃NC in the presence of C₇H₇⁺BF₄^–. The isonitrile complexes have been characterized by i.r. and n.m.r. spectroscopy.