Acetonitrile activation in di-iron μ-carbyne complexes: synthesis and structure of the cyanomethyl complex [Fe2(μ-CNMe2)(μ-CO)(CO)(CH2CN)(Cp)2]

Reactions of [Fe2{μ-CN(Me)R}(μ-CO)(CO)(NCMe)(Cp)2]SO3CF3 (R=Me, 2a; CH2Ph, 2b; 2,6-Me2C6H32c) with LiBun afford the corresponding cyanomethyl complexes [Fe2{μ-CN(Me)R}(μ-CO)(CO)(CH2CN)(Cp)2] (3a–c), presumably via deprotonation and rearrangement of the coordinated acetonitrile. Likewise, the benzylnitrile complex [Fe2{μ-CN(Me)(2,6-Me2C6H3)}(μ-CO)(CO)(NCCH2Ph)(Cp)2]SO3CF3 yields [Fe2{μ-CN(Me)(2,6-Me2C6H3)}(μ-CO)(CO)(CH(CN)Ph)(Cp)2] (3d). The X-ray molecular structure of 3a has shown the expected stereogeometry and significant asymmetry of the bridging ligands. Deprotonation and rearrangement of the coordinated MeCN are not observed in the thiocarbyne complex [Fe2(μ-CSMe)(μ-CO)(CO)(NCMe)(Cp)2]SO3CF3 (5) in spite of the similarities with 2a–c. However, compound 5 readily reacts with Li2Cu(CN)R2 (R=Me, Ph) to form the thiocarbene complexes [FeSme}(μ-CO)(CO)(Cp)2] (6a–b), with displacement of the acetonitrile ligand.