Addition of isocyanides at diiron μ-vinyliminium complexes:: Synthesis of novel ketenimine-bis(alkylidene) complexes

Reactions of the vinyliminium complexes [Fe-2{mu-eta(1):eta(3)-C-gamma(R')C-beta(H)C alpha N(Me)(R)}(mu-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 C-beta-H proton and to isocyanide addition with formation of a carbon-carbon double bond. The observed products are the ketenimine-bis(alkylideiie) complexes [Fe-2{mu-eta(1):eta(2)-C-gamma(R')C-beta(CNR)C alpha N(Me)(R)}(mu-CO)-(CO)(CP)(Cp)(2)] (R = Xyl, R' = Me, R = Xyl, 2a; R = Xyl, R' = CO2Me, R = Xyl, 2b; R = Xyl, R' = CO2Me, R = Bu-t, 2c; R = Xyl, R' = CO2Me, R = 4-C6H4CN, 2d; R = 4-C6H4OMe, R' = CO2Me, R = Bu-t, 2e), obtained in 60-70% yields. Conversely, the vinyliminium complex [Fe-2{mu-eta(1):eta(3)- C-gamma(CO2Me)C-beta(H)C alpha N(Me)(2)}(mu-CO)(CO)(Cp)(2)][SO3CF3] (1d) undergoes double isocyanide addition. Reactions of Id with a 2-fold excess of CNXyl or CNBut, in the presence of NaH, afford [Fe(CO)(Cp)C-alpha(NMe2)C-beta(CNXyl)C-gamma(CO2Me)C(NXy)Fe(CO)(Cp)] (3) and [Fe(CO)(Cp)C(NBut)C-alpha(NMe2)-C beta C gamma(CO2Me)Fe(Cp)(CO)CNBut] (4), respectively. Finally, the vinyliminium complex [Fe-2{mu-eta(1):eta(3)-C-gamma(H)C-beta(H)C alpha N(Me)(2)}(mu-CO)(CO)(CP)(2)][SO3CF3] (1e), treated with with CNBut and NaH, yields a mixture of the diiron aminocarbyne complexes [Fe-2{mu-CN(Me)(2)}(mu-CO)(CO)(CP)(C5H5CH2CN)(CNBut)], (6) and [Fe-2{mu-CN(Me)(2)}(mu-CO)(CO)(Cp)(2)(CNBut)] (5). The molecular structures of 2a,b, 3.1.5CH(2)Cl(2), 4, and 6.0.5Et(2)O have been ascertained by X-ray diffraction studies.