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 PhP(O)N(CH2Ph)CH3 1 and 2,6-di-tert-butyl-4-methylphenol 5 leads to the formation of the mixed dimer [(Ph2P(O)N(CH2Ph)CH3)(LiOC6H2)-Li-.-2.6-{C(CH3)(3)}(2)-4-(CH3C7H8)-C-.]( 2) 6. 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 (H-1, Li-7, C-13, P-31) 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.