Addition of Isocyanides at Diiron m-Vinyliminium Complexes: Synthesis of Novel Ketenimine-Bis(alkylidene) Complexes

Reactions of the vinyliminium complexes [Fe2{m-h1:h3-Cg(R')Cb(H)CaN(Me)(R)}(m-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 Cb-H proton and to isocyanide addn. with formation of a carbon-carbon double bond. The obsd. products are the ketenimine-bis(alkylidene) complexes [Fe2{m-h1:h2-Cg(R')Cb(CNR'')CaN(Me)(R)}(m-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{m-h1:h3-Cg(CO2Me)Cb(H)CaN(Me)2}(m-CO)(CO)(Cp)2][SO3CF3] (1d) undergoes double isocyanide addn. Reactions of 1d with a 2-fold excess of CNXyl or CNBut, in the presence of NaH, afford [Fe(CO)(Cp)Ca(NMe2)Cb(CNXyl)Cg(CO2Me)C(NXy)Fe(CO)(Cp)] (3) and [Fe(CO)(Cp)C(NBut)Ca(NMe2)CbCg(CO2Me)Fe(Cp)(CO)CNBut] (4), resp. Finally, the vinyliminium complex [Fe2{m-h1:h3-Cg(H)Cb(H)CaN(Me)2}(m-CO)(CO)(Cp)2][SO3CF3] (1e), treated with CNBut and NaH, yields a mixt. of the diiron aminocarbyne complexes [Fe2{m-CN(Me)2}(m-CO)(CO)(Cp)(C5H5CH2CN)(CNBut)], (6) and [Fe2{m-CN(Me)2}(m-CO)(CO)(Cp)2(CNBut)] (5). The mol. structures of 2a,b, 3×1.5CH2Cl2, 4, and 6×0.5Et2O have been ascertained by x-ray diffraction studies.