Trimethylphosphine as a reactive solvent: synthesis, crystal structures, and reactions of [Ta(PMe3)3(η2-CH2PMe2)(η2-CHPMe2)] and [W(PMe3)4(η2-CH2PMe2)H] and related studies

Abstract

Reduction of WCl₆, MoCl₅, TaCl₅, ReCl₅, and RuCl₃ using sodium sand in pure trimethylphosphine as a reactive solvent gives the compounds [W(PMe₃)₄(η²-CH₂PMe₂)H], [Mo(PMe₃)₅H₂], [Ta(PMe₃)₃(η²-CH₂PMe₂)(η²-CHPMe₂)], [Re(PMe₃)₅H], [Ru(PMe₃)₃(η²-CH₂PMe₂)H], and [(PMe₃)₃ HRu(µ-CH₂PMe₂)₂RuH(PMe₃)₃], respectively. The crystal structures of the tungsten and tantalum compounds have been determined. The previously unknown ligand η²-CHPMe₂ is shown to be present in the tantalum compound. The reduction of WCl₆ in PMe₃ by magnesium is shown to proceed in the sequence [W(PMe₃)₃Cl₄], [{W(PMe₃)₃Cl₂}₂], [W(PMe₃)₄Cl₂]. Reduction of [W(PMe₃)₃Cl₄] with sodium sand under hydrogen gives [W(PMe₃)₄Cl₂H₂]. The compound [W(PMe₃)₄(η²-CH₂PMe₂)H] reacts with butadiene giving cis-[W(PMe₃)₂(η-C₄H₆)₂] and with cyclopentadiene forming [W(η-C₅H₅)(PMe₃)₃H] and [W(η-C₅H₅)₂H₂]. Variable-temperature n.m.r. studies on [W(PMe₃)₄(η²-CH₂PMe₂)H] show it to be fluxional. Reduction of RUCl₃ in trimethylphosphine–cyclopentene gives [Ru(PMe₃)₄(σ-[graphic omitted]H₂)H]. The compound [W(PMe₃)₃H₆] with spiro[2.4]hepta-4,6-diene gives [W(η-C₅H₄Et)(PMe₃)₃H].