Synthesis and reactivity with amines of new diiron alkynyl methoxy carbene complexes

The newdiironalkynylmethoxycarbenecomplexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO){C(OMe)CCR′}(Cp)2]+ (R = 2,6-Me2C6H3 (Xyl), R′ = Tol, 3a; R = Xyl, R′ = Ph, 3b; R = Xyl, R′=Bun, 3c; R = Xyl, R′=SiMe3, 3d; R = Me, R′ = Tol, 3e; R = Me, R′ = Ph, 3f) are obtained in two steps by addition of R′CCLi (R′ = Tol, Ph, Bun, SiMe3) to the carbonyl aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)2(Cp)2]+ (R = Xyl, 1a; Me, 1b), followed by methylation of the resulting alkynyl acyl compounds [Fe2{μ-CN(Me)(R)}(μ-CO)(CO){C(O)CCR′}(Cp)2] (R = Xyl, R′ = Tol, 2a; R = Xyl, R′ = Ph, 2b; R = Xyl, R′ = Bun, 2c; R = Xyl, R′ = SiMe3, 2d; R = Me, R′ = Tol, 2e; R = Me, R′ = Ph, 2f). Complexes3 react with secondary amines (i.e., Me2NH, C5H10NH) to give the 4-amino-1-metalla-1,3-dienes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO){C(OMe)CHC(R′)(NMe2)}(Cp)2]+ (R = Xyl, R′ = Tol, 4a; R = Xyl, R′ = Ph, 4b; R = Me, R′ = Ph, 4c) and [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(Tol)(NC5H10)}(Cp)2]+, 5. The addition occurs stereo-selectively affording only the E-configured products. Analogously, addition of primary amines R′NH2 (R′ = Ph, Et, Pri) affords the 4-(NH-amino)-1-metalla-1,3-diene complexes [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(R)(NHR′)}(Cp)2]+ (R = Ph, 6a; Et, 6b; Pri, 6c). In the case of6a, only the E isomer is formed, whereas a mixture of the EandZ isomers is present in the case of6b,c, with prevalence of the latter. Moreover, the two isomeric forms exist under dynamic equilibrium conditions, as shown by VT NMR studies. Complexes6 are deprotonated by strong bases (e.g., NaH) resulting in the formation of the neutral vinyl imine complexes [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(NR)(Tol)}(Cp)2] (R = Ph, 7a; Et, 7b; Pri, 7c); the reaction can be reverted by addition of strong acids. X-ray crystal structures have been determined for 3a[CF3SO3] · Et2O, 4c[CF3SO3], 6a[BF4] · CH2Cl2, 6c[CF3SO3] · 0.5Et2Oand7a · CH2Cl2.