Methylene-Linked AnilideBis(aryloxide) Ligands: Lithium, Sodium, Potassium, Chromium(III), and Vanadium(III) Ligation

The anilide–bis­(aryloxide)
proligands H3[ONOR] (where H3[ONOR]
= 2,6-(3-R1-5-R2-2-hydroxybenzyl)-4-tert-butyl-N-tolyl-aniline; H3[ONOtBu], R1 = tBu, R2 = Me; H3[ONOMe], R1 = Me, R2 = tBu; H3[ONOMe2], R1 = R2 = Me) were synthesized
from 2-bromo-5-tert-butyl-isophthalic acid dimethyl
ester in three steps in multigram scale. The ligand precursor H3[ONOtBu] was readily doubly and triply deprotonated with alkali metal reagents
to generate the related derivatives M2[H­(ONOtBu)] and M3[ONOtBu] (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[ONOtBu] with MCl3(THF)3 (M = Cr, V; THF = tetrahydrofuran) afforded [(ONOtBu)­CrCl­(THF)­{Li­(THF)}]
(5) and [(ONOtBu)­V­(THF)] (6). The vanadium complex 6 reacted readily with 2-butyne, styrene oxide, and mesityl
azide, yielding [(ONOtBu)­V­(η2-MeCCMe)] (7), [(ONOtBu)­V­(O)] (8), and [(ONOtBu)­V­(NMes)] (9), respectively. The solid-state structures
of H3[ONOtBu] and metal complexes were determined by X-ray crystallography.
The [ONOtBu]
ligand adopts a u-shaped structure in solution and solid state.