A convenient method for selective substitutions at the backbone of a co-ordinated imidazolylphosphine P–N ligand. Single crystal X-ray analyses of [Mo(CO)4(MeImCH2PPh2)] and its ethyl substituted derivative [Mo(CO)4(MeImCHEtPPh2)]†

The complex [Mo(CO)4(PN)] 1 was synthesized by refluxing [Mo(CO)6], with 2-(diphenylphosphinomethyl)-1-methylimidazole (PN) in ethanol in the presence of NaBH4. The co-ordinated PN is selectively deprotonated to afford a carbanion [Mo(CO)4(MeImCHPPh2)]– 1a when 1 is treated with strong bases such as methyllithium or n-butyllithium at room temperature. The carbanion 1a readily reacted with deuterium oxide, methyl iodide, ethyl iodide, allyl bromide, and trimethylsilyl chloride to give [Mo(CO)4(MeImCHRPPh2)] (R = D 2, Me 3, Et 4, CH2CHCH2 5 or SiMe3 6). Treatment of 1a with chlorodiphenylphosphine and benzoyl chloride gave the corresponding derivatives [Mo(CO)4{MeImCH(PPh2)2}]·0.5H2O 7 and [Mo(CO)4{MeImCH(COPh)PPh2}]·H2O 8 respectively, both containing an additional free donor site. However, slow addition of acetyl chloride to a tetrahydrofuran solution of 1a gave the O-acetyl enolate derivative [Mo(CO)4{MeImCCMe(OCOMe)PPh2}]·0.5H2O 9 instead of an acetyl derivative. The 1H and 31P NMR spectra indicated the presence of two geometric isomers (Z and E) for complex 9. All of these complexes were fully characterized by IR, 1H and 31P NMR. The molecular structures of complex 1 and its ethyl substituted derivative 4 have also been studied by single crystal X-ray analyses.