Syntheses of di-hydrocarbyl derivatives of carbonyl phosphine complexes of iron

Complexes cis,trans-Fe(CO)2(PMe3)2RR′ (R = CH3, R′ = Ph (2); R = CH3, R′ = CHdouble bond; length as m-dashCH2 (3); R = CHdouble bond; length as m-dashCH2, R′ = Ph (4); R = R′ = CHdouble bond; length as m-dashCH2 (5); R = R′ = CH3 (6)) were prepared by reaction of cis,trans-Fe(CO)2(PMe3)2RCl (1) with organolithium reagents LiR′. All complexes were characterized in solution by IR and 1H, 31P and, in a few cases, 13C NMR mono- and bi-dimensional spectroscopies. Complexes 5 and 6 were structurally characterized by X-ray diffractometric methods. In solution complexes 2, 3 and 4 undergo slowly coupling of the σ-hydrocarbyl substituents leading to Fe(CO)3(PMe3)2 and other decomposition products. Complex 6 was very stable in solution in the absence of nucleophiles and in the solid state. Complex 5 transformed through intramolecular coupling of the vinyl groups into Fe(CO)(PMe3)2(η4-butadiene) (7), which was characterized in solution by IR and NMR spectroscopies.