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)]†

Abstract

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.