CN coupling between μ-aminocarbyne and nitrile ligands promoted by tolylacetylide addition to [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO)(NCCMe3)(Cp)2][SO3CF3]: Formation of a novel bridging η1:η2 allene-diaminocarbene ligand

The reaction of the μ-aminocarbyne complex [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO)(NCCMe3)(Cp)2][SO3CF3] (2) (Xyl=2,6-Me2C6H3) with tolylacetylide, followed by treatment with HSO3CF3 affords the complex [Fe2{μ-η1:η3C(Tol)CC(CMe3)N(H)CN(Me)(Xyl)}(μ-CO)(CO)(Cp2)][SO3CF3] (3) (Tol=4-MeC6H4). The X-ray molecular structure of 3 reveals the peculiar character of the bridging ligand, which exhibits both η1:η2 allene and aminocarbene nature. The formation of 3 proceeds through several intermediate species, which have been detected by IR spectroscopy. Addition of HSO3CF3 at an early stage of the reaction between 2 and LiCCTol leads to the formation of the imine complex [Fe2{μ-CN(Me)Xyl}(μ-CO)(CO){NHC(CCTol)CMe3}(Cp)2][SO3CF3] (6) indicating that the first step of the reaction consists in the acetylide addition at the coordinated NCCMe3. The molecular structure of 6 has been elucidated by an X-ray diffraction study.