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, [1aNCMe]CF3SO3; R = Me, [1bNCMe]CF3SO3; R = Cy, [1cNCMe]CF3SO3; R = CH2Ph, [1dNCMe]CF3SO3), freshly prepared from tricarbonyl precursors [1a–d]CF3SO3, 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 [1aNCMe–1cNCMe]CF3SO3 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 [1aNCMe]CF3SO3 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 trans-6b 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.