Ethynylferrocene insertion into Fe–C bond in bridging aminocarbyne diiron complexes: New triiron vinyliminium complexes

The μ-aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (R = Me, 1a; Xyl, 1b; Xyl = 2,6-Me2C6H3) react with ethynylferrocene to give the corresponding bridging vinyliminium complexes [Fe2{μ-η1:η3-Cdouble bond; length as m-dashN(Me)(R)CHC(Fc)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Me, 2a; R = Xyl, 2b). Insertion of the ethynylferrocene in the metal–carbyne bond is regiospecific, and leads to the formation of only one isomer. Complexes 2a and 2b undergo hydride addition (by NaBH4) affording the enaminoalkylidene complex [Fe2{μ-η1:η3-C(H)(N(Me)2)CHC(Fc)}(μ-CO)(CO)(Cp)2] (3a) and the bis-alkylidene [Fe2{μ-η1:η2-C(N(Me)(Xyl))CH2C(Fc)}(μ-CO)(CO)(Cp)2] (3b), respectively. Upon treatment with NaH, compounds 2a and 2b undergo fragmentation, affording the 1-metalla-2-aminocyclopenta-1,3-dien-5-one complexes [Fe(CO)(Cp){C(N(Me)(R))}CHC(Fc)C(O)}] (R = Me, 4a; R = Xyl, 4b). The molecular structures of 2b, 3b and 4b have been determined by X-ray diffraction studies.