Addition of Alkynes to Zwitterionic μ-Vinyliminium Diiron Complexes: New Selenophene (Thiophene) and Vinyl Chalcogenide Functionalized Bridging Ligands

Zwitterionic vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(E)CαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = R′ = Me, E = Se, 1a; R = Xyl, R′ = Tol, E = Se, 1b; R = Xyl, R′ = Tol, E = S, 2a; R = Xyl, R′ = Tol, E = S, 2b; Tol = 4-MeC6H4, Xyl = 2,6-Me2C6H3) undergo alkyne addition by different reaction modes. Complexes 1a and 2a undergo 1,3 dipolar cycloaddition with alkynes [HCCCO2Me and C2(CO2Me)2], affording new 1-(2-amino)-seleno(thio)phene-alkylidene diiron complexes [Fe2{μ-κ1(N):η1(C):η1(C):-Cγ(R′)CβEC(CO2Me)C(R′′)CαN(Me)(R)}(μ-CO)(CO)(Cp)2] (R = R′ = Me, E = Se, R′′ = CO2Me, 3a; R = R′ = Me, E = Se, R′′ = H, 3b; R = Me, R′ = Tol, E = S, R′′ = CO2Me, 4). The hemilabile character of the bridging ligand in 3a is investigated by reaction with CNBut, which replaces NMe2 coordination, affording [Fe2{μ-Cγ(Me)CβSeC(CO2Me)C(CO2Me)CαN(Me)2}(μ-CO)(CO)(CNBut)(Cp)2] (5). Complexes 2a and 2b react with two equivalents of HCCCO2Me, leading to the formation of [Fe2{μ-κ1(O):η1(C):η3(C)-Cδ(CCCO2Me)Cγ(R′)Cβ(SCHCHCO2Me)Cα(O)N(Me)(Xyl)}(μ-CO)(Cp)2] (R′ = Tol, 6a; R′ = Me, 6b). Finally, complexes 1b, 2a, and 2b react with different alkynes, in the presence of NH4PF6, affording the vinyl sulfide and vinyl selenide vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(ECR′′CHCO2Me)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2][PF6] (R′ = Tol, E = S, R′′ = H, 7a; R′ = Me, E = S, R′′ = H, 7b; R′ = Tol, E = S, R′′= CO2Me, 7c; R′ = Me, E = S, R′′ = CO2Me, 7d; R′ = Tol, E = Se, R′′ = H, 8a; R′ = Tol, E = Se, R′′ = CO2Me, 8b). The molecular structures of 3a, 5, and 6b have been elucidated by X-ray diffraction.