Addition of isocyanides at diiron m-vinyliminium complexes: synthesis of novel ketenimine-bis(alkylidene) complexes

Reactions of the vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(H)CαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Xyl, R′ = Me, 1a; R = Xyl, R′ = CO2Me, 1b; R = 4-C6H4OMe, R′ = CO2Me, 1c; Xyl = 2,6-Me2C6H3) with isocyanides (CNR′′), in the presence of NaH, lead to abstraction of the Cβ−H proton and to isocyanide addition with formation of a carbon−carbon double bond. The observed products are the ketenimine−bis(alkylidene) complexes [Fe2{μ-η1:η2-Cγ(R′)Cβ(CNR′′)CαN(Me)(R)}(μ-CO)(CO)(Cp)2] (R = Xyl, R′ = Me, R′′ = Xyl, 2a; R = Xyl, R′ = CO2Me, R′′ = Xyl, 2b; R = Xyl, R′ = CO2Me, R′′ = But, 2c; R = Xyl, R′ = CO2Me, R′′ = 4-C6H4CN, 2d; R = 4-C6H4OMe, R′ = CO2Me, R′′ = But, 2e), obtained in 60−70% yields. Conversely, the vinyliminium complex [Fe2{μ-η1:η3-Cγ(CO2Me)Cβ(H)CαN(Me)2}(μ-CO)(CO)(Cp)2][SO3CF3] (1d) undergoes double isocyanide addition. Reactions of 1d with a 2-fold excess of CNXyl or CNBut, in the presence of NaH, afford [Fe(CO)(Cp)Cα(NMe2)Cβ(CNXyl)Cγ(CO2Me)C(NXy)Fe(CO)(Cp)] (3) and [Fe(CO)(Cp)C(NBut)Cα(NMe2)CβCγ(CO2Me)Fe(Cp)(CO)CNBut] (4), respectively. Finally, the vinyliminium complex [Fe2{μ-η1:η3-Cγ(H)Cβ(H)CαN(Me)2}(μ-CO)(CO)(Cp)2][SO3CF3] (1e), treated with with CNBut and NaH, yields a mixture of the diiron aminocarbyne complexes [Fe2{μ-CN(Me)2}(μ-CO)(CO)(Cp)(C5H5CH2CN)(CNBut)], (6) and [Fe2{μ-CN(Me)2}(μ-CO)(CO)(Cp)2(CNBut)] (5). The molecular structures of 2a,b, 3·1.5CH2Cl2, 4, and 6·0.5Et2O have been ascertained by X-ray diffraction studies.