Addition of protic nucleophiles to alkynyl methoxy carbene ligands in diiron complexes

Different protic nucleophiles (i.e.Ph2Cdouble bond; length as m-dashNH, PhSH, MeCO2H, PhOH) can be added to the Ctriple bond; length of mdashC bond of [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)Ctriple bond; length of mdashCTol}(Cp)2][SO3CF3] (1), affording new diiron alkenyl methoxy carbene complexes.The additions of Ph2Cdouble bond; length as m-dashNH and MeCO2H are regio and stereoselective, resulting in the formation of the 5-aza-1-metalla-1,3,5-hexatriene [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(OMe)CβHdouble bond; length as m-dashCγ(Tol)(Ndouble bond; length as m-dashCPh2)}(Cp)2][SO3CF3] (2), and the 2-(acyloxy)alkenyl methoxy carbene complex [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(OMe)CβHdouble bond; length as m-dashCγ(Tol)OC(O)Me)}(Cp)2][CF3SO3] (5); the E isomer of the former and the Z of the latter are formed exclusively.Conversely, the addition of PhSH is regio but not stereoselective; thus, both the E and Z isomers of [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(OMe)CβHdouble bond; length as m-dashCγ(Tol)(SPh)}(Cp)2][SO3CF3] (3) are formed in comparable amounts.Compounds 3 and 5 are demethylated upon chromatography through Al2O3, resulting in the formation of the acyl complexes [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(O)CβHdouble bond; length as m-dashCγ(Tol)(SPh)}(Cp)2] (4) and [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(O)CβHdouble bond; length as m-dashCγ(Tol)OC(O)Me}(Cp)2] (6), respectively, both with a Z configured Cβdouble bond; length as m-dashCγ bond.Finally, the reaction of 1 with PhOH proceeds only in the presence of an excess of Et3N affording the 2-(alkoxy)alkenyl acyl complex [Fe2{μ-CN(Me)(Xyl)}(μ- CO)(CO){Cα(O)CβHdouble bond; length as m-dashCγ(Tol)(OPh)}(Cp)2] (7). The crystal structures of 4 · CH2Cl2 and 7 · 0.5CH2Cl2 have been determined by X-ray diffraction experiments.