X-ray and multinuclear NMR study of the mixed aggregate [(Ph2P(O)N(CH2Ph)CH3) · LiOC6H2-2,6-{C(CH3)3}2-4-CH3) · C7H8]2: a model for the directed metalation of phosphinamides

The addition of LiBun to a toluene solution of Ph2P(O)N(CH2Ph)CH31 and 2,6-di-tert-butyl-4-methylphenol 5 leads to the formation of the mixed dimer [(Ph2P(O)N(CH2Ph)CH3) · LiOC6H2-2,6-{C(CH3)3}2-4-CH3) · C7H8]26. The single crystal X-ray structure shows that two lithium aryloxide moieties dimerize giving rise to a Li2O2 core in which each lithium atom is additionally coordinated to a phosphinamide 1 ligand. The multinuclear magnetic resonance study (1H, 7Li, 13C, 31P) indicates that the solid-state structure is preserved in toluene solution. Complex 6 may be considered as a model for the pre-complexation step preceding the metalation of phosphinamides by an organolithium base.