C-N coupling between µ-aminocarbyne and nitrile ligands promoted by tolylacetylide addition to [Fe2CN(Me)(Xyl)}(CO)(CO)(NCCMe3)(Cp)2][SO3CF3]: formation of a novel bridging allene-diaminocarbene ligand

The reaction of the mu-aminocarbyne complex [Fe-2{mu-CN(Me)(Xyl)}(mu-CO)(CO)(NCCMe3)(CP)(2)][SO3CF3] (2) (Xyl = 2,6-Me2C6H3) with tolylacetylide, followed by treatment with HSO3CF3 affords the complex [Fe-2{mu-eta(1):eta(3)C(Tol)double bondCdouble bondC(CMe3)N(H)CN(Me)(Xyl)}(mu-CO)(CO)(Cp-2)][SO3CF3] (3) (Tol = 4-MeC6H4). The X-ray molecular structure of 3 reveals the peculiar character of the bridging ligand, which exhibits both eta(1):eta(2) 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 LiCdropCTol leads to the formation of the imine complex [Fe-2{mu-CN(Me)Xyl}(mu-CO)(CO){NHC(CdropCTol)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.