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)double bond; length as m-dashC(Me)C(O)OMe}(μ-CO)(Cp)2] (2) has been obtained from the diiron bridging vinyliminium [Fe2{μ-η1:η3–C(Me)double bond; length as m-dashC(H)Cdouble bond; length as m-dashN(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (1; Xyl = 2,5-C6H3Me2) upon treatment with NaH in the presence of CH2double bond; length as m-dashCdouble bond; length as m-dashCMe2, 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.