Assembly and incorporation of a CO2Me group into a bridging vinyliminium ligand in a diiron complex

The diiron complex Fe₂{μ-к¹(O):η¹(C):η³(C)-C(N(Me)(Xyl))C(H)C(Me)C(O)OMe}(μ-CO)(Cp)₂] (2) has been obtained from the diiron bridging vinyliminium Fe₂{μ-η¹:η³-C(Me)C(H)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂]SO₃CF₃] (1; Xyl = 2,5-C₆H₃Me₂) upon treatment with NaH in the presence of CH₂CCMe₂, followed by chromatography on alumina with MeOH as eluent. The reaction consists in the incorporation of a methylcarboxylate unit, assembled from CO and MeO⁻, into the bridging vinyliminium ligand. The resulting complex 2 exhibits a C₄ fragment bridging the two iron centres through the carbonyl oxygen atom and the allylidene moiety.The X-ray molecular structure of 2 has been determined.