Reactivity studies of a soluble LiH-complex and non-spectator behaviour of its stabilising phosphinoamide ligand

Abstract

We have investigated and compared the reactivity of the phosphinoamide stabilized hydrocarbon-soluble LiH complex [(LLi)₄(LiH)₄] 1 (L = [Ph₂PNDip], Dip = 2,6-ⁱPr₂C₆H₃) and the lithium phosphinoamide [LLi] 2 towards some unsaturated organic substrates. The complexes [(LSiMe₂OLi)₂(HDCCLi)₂] 3 (DCC = CyNCNCy, Cy = cyclohexyl) and [(HDCC)₆Li₈O] 4 were obtained from reactions of 1 with DCC, and the complexes [{LN(Ph)N(Ph)Li}₂] 5 and [{PhN(Li)–N(Li)Ph}₄] 7 were obtained from reactions of 1 with azobenzene. Complex 5 was furthermore obtained in good yield from 2 and azobenzene, and was converted to the solvate [LN(Ph)N(Ph)Li(THF)] 6. Complex 7 could be independently synthesized from lithium metal and azobenzene. Complex 1 undergoes hydrolithiation reactions with some substrates, as evidenced by the formation of complexes 3, 4, and indirectly by 7, but also takes part in addition reactions of the stabilizing phosphinoamide ligand onto substrates as shown by the isolation of complexes 3 and 5. The crystal structures of complexes 3, 5, 6, 7 and [LLi(THF)₃] are reported.