Diiron Aminocarbyne Complexes with NCE^- Ligands (E = O, S, Se)

Diiron μ-aminocarbyne complexes [Fe₂Cp₂(NCMe)(CO)(μ-CO){μ-CN(Me)(R)}]CF₃SO₃ (R = Xyl, [1a; R = Me, [1b; R = Cy, [1c; R = CH₂Ph, [1d), freshly prepared from tricarbonyl precursors [1a-d]CF, reacted with NaOCN (in acetone) and NBu₄SCN (in dichloromethane) to give [Fe₂Cp₂(kN-NCO)(CO)(μ-CO){μ-CN(Me)(R)}] (R = Xyl, 2a; Me, 2b; Cy, 2c) and [Fe₂Cp₂(kN-NCS)(CO)(μ-CO){μ-CN(Me)(CH₂Ph)}], 3 in 67-81% yields via substitution of the acetonitrile ligand. The reaction of [1a with KSeCN in THF at reflux temperature led to the cyanide complexes [Fe₂Cp₂(CN)(CO)(μ-CO){μ-CNMe(R)}], 6a-c (45-67%). When the reaction of [1a with KSeCN was performed in acetone at room temperature, subsequent careful chromatography allowed the separation of moderate amounts of [Fe₂Cp₂(kSe-SeCN)(CO)(μ-CO){μ-CN(Me)(Xyl)}], 4a, and [Fe₂Cp₂(kN-NCSe)(CO)(μ-CO){μ-CN(Me)(Xyl)}], 5a. All products were fully characterized by elemental analysis, IR, and multinuclear NMR spectroscopy; moreover, the molecular structure of was ascertained by single crystal X-ray diffraction. DFT calculations were carried out to shed light on the coordination mode and stability of the {NCSe-} fragment.