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

摘要

We have investigated and compared the reactivity of the phosphinoamide stabilized hydrocarbon-soluble LiH complex (LLi)_4(LiH)_4 1 (L = Ph_2PNDip, Dip = 2,6-~iPr_2C_6H_3) and the lithium phosphinoamide LLi 2 towards some unsaturated organic substrates. The complexes (LSiMe_2OLi)_2(HDCCLi)_2 3 (DCC = CyNCNCy, Cy = cyclohexyl) and (HDCC)_6Li_8O 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.