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

Zwitterionic vinyliminium complexes [Fe2{u-eta1:eta3-C(R’)=C(E)C=N(Me)(R)}(-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-1(N):1(C):1(C):-C(R’)CEC(CO2Me)=C(R’’)CN(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 replace NMe2 coordination affording [Fe2{μ-C(Me)CSeC(CO2Me)=C(CO2Me)CN(Me)2}(μ-CO)(CO)(CNBut)(Cp)2] (5). Complexes 2a, 2b react with two equivalents of HCCCO2Me, leading to the formation in formation of [Fe2{-1(O):1(C):3(C)-C(CCCO2Me)C(R’)C(SCH=CHCO2Me)CON(Me)(Xyl)}(-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 sufide and vinyl selenide vinyliminium complexes [Fe2{μ-1:3-C(R’)=C(ECR’’=CHCO2Me)C=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.