Construction of Two-Faced (Hetero)hydrocarbyl Diiron Complexes Mediated by the Interplay of Ligands

Abstract

The functionalized allylidene complex [Fe 2 Cp 2 (CO)(μ-CO){μ-η 1 :η 3 -C γ (Fc)-C β HC α (CN)NMe 2 }], 1 [Cp = η 5 -C 5 H 5 ; Fc = CpFe(η 5 -C 5 H 4 )], reacted with isocyanides (CNR), in isopropanol solution at ca. 100 °C, to give the CO-substitution products [Fe 2 Cp 2 (CO)(μ-CNR){μ-η 1 :η], which were isolated in 61−84% yields. The bridging coordination of CNR in 2a−c is forced by a stabilizing electrostatic interaction between the nitrogen lone pair belonging to the {NMe 2 } group and the terminal CO ligand. Isocyanide methylation with methyl triflate proceeded with the inversion of stereochemistry at the C α carbon and led to [Fe 2 Cp 2 (CO){μ-CN(Me)R}{μ-η 1 :η), containing bridging allylidene and aminocarbyne ligands (68−74% yields). All products were fully characterized by IR and multinuclear NMR spectroscopy, and the structures of 2a and [3a]CF 3 SO 3 were elucidated by X-ray diffraction studies. Density functional theory (DFT) calculations were extensively carried out to shed light on structural, mechanistic, and thermodynamic features.