Methylene-linked anilide-bis(aryloxide) ligands: lithium, sodium, potassium, chromium(III), and vanadium(III) ligation.

The anilide-bis(aryloxide) proligands H3[ONO(R)] (where H3[ONO(R)] = 2,6-(3-R(1)-5-R(2)-2-hydroxybenzyl)-4-tert-butyl-N-tolyl-aniline; H3[ONO(tBu)], R(1) = (t)Bu, R(2) = Me; H3[ONO(Me)], R(1) = Me, R(2) = (t)Bu; H3[ONO(Me2)], R(1) = R(2) = Me) were synthesized from 2-bromo-5-tert-butyl-isophthalic acid dimethyl ester in three steps in multigram scale. The ligand precursor H3[ONO(tBu)] was readily doubly and triply deprotonated with alkali metal reagents to generate the related derivatives M2[H(ONO(tBu))] and M3[ONO(tBu)] (M = Li, Na, K). The extent of ligand deprotonation is observed to depend on the choice of deprotonating reagents and solvents. Transmetalation reaction of the trilithium derivative Li3[ONO(tBu)] with MCl3(THF)3 (M = Cr, V; THF = tetrahydrofuran) afforded [(ONO(tBu))CrCl(THF){Li(THF)}] (5) and [(ONO(tBu))V(THF)] (6). The vanadium complex 6 reacted readily with 2-butyne, styrene oxide, and mesityl azide, yielding [(ONO(tBu))V(η(2)-MeCCMe)] (7), [(ONO(tBu))V(O)] (8), and [(ONO(tBu))V(NMes)] (9), respectively. The solid-state structures of H3[ONO(tBu)] and metal complexes were determined by X-ray crystallography. The [ONO(tBu)] ligand adopts a u-shaped structure in solution and solid state.