Growing the Molecular Architecture at Alkynyl(amino)carbene Ligands in Diiron μ-Aminocarbyne Complexes

The diiron μ-aminocarbyne imidoyl complexes [Fe2(μ-CN(Me)(R))(μ-CO)(CO)(C(C≡CR')=NXyl)Cp2] [R = Xyl, R' = Ph (1a);[1] R = Xyl, R' = Tol (1b);[1] R = Me, R' = Ph (1c); R = Me, R' = SiMe3 (1d); Xyl = 2,6-C6H3Me2, Tol = 4-C6H4Me] have been prepared by the addition of lithium acetylides to precursors containing a terminal isocyanide ligand. The treatment of 1a-c with CF3SO3CH3 afforded the alkynyl(amino)carbene derivatives [Fe2(μ-CN(Me)(R))(μ-CO)(CO)(C(C≡CR')N(Me)(Xyl))Cp2][SO3CF3] [R = Me, R' = Ph (2a); R = Xyl, R' = Ph (2b); R = Xyl, R' = Tol (2c)] in high yields. The reactions of 2b,c with CH3OH/NaBF4, NH2R and NaBH4 led to [Fe2(μ-CN(Me)(Xyl))(μ-CO)(CO)(C(CH=C(Ph)OMe)N(Me)(Xyl))Cp2][BF4] (3), [Fe2(μ-CN(Me)(Xyl))(μ-CO)(CO)(C(CH=C(Tol)NHR)N(Me)(Xyl))Cp2][SO3CF3] [R = Et (4a); R = Ph (4b)], and [Fe2(μ-CN(Me)(Xyl))(μ-CO)(CO)(C(CH=CHTol)N(Me)(Xyl))Cp2][SO3CF3] (5) in yields of 65-80%. Complexes 3-5 were formed by the selective functionalization of the alkynyl group in 2b,c. Complex 2c reacted with NaCH(CN)2/CH2(CN)2 and NaCH(CO2Me)2 to yield [Fe2(μ-CN(Me)(Xyl))(μ-CO)(CO)(C(N(Me)(Xyl))CH=C(Tol)C(CN)C(NH2)C(CN)2)Cp2] (6) and [Fe2(μ-C(NXyl)C(C(Tol)=C(CO2Me)2)CN(Me)(Xyl))(μ-CO)2Cp2] (7) in yields of 65 and 60%, respectively. All the products were purified by alumina chromatography, alumina being presumably involved in the formation of 3, and characterized by elemental analysis and IR and NMR spectroscopy. The structures of 2b, 3, 5, and 6 were ascertained by single-crystal X-ray diffraction analysis.