3d Early Transition Metal Complexes Supported by a New Sterically Demanding Aryloxide Ligand

The bulky aryloxide 2,6-bis(diphenylmethyl)-4-tert-butylphenol [HOArtBu] (1) can be synthesized from 4-tert-butylphenol and benzhydrol in solvent-free conditions and obtained pure in 91% yield. Deprotonation of HOArtBu is accomplished with M(N(SiMe3)(2)) (M = Na, Li), yielding the corresponding salts of the aryloxide [MOArtBu (M+ = Na (2), Li(3)) in 83% and 73% yield, respectively. Facile salt formation of the aryloxide ligand allows for transmetalation to a variety of metal halides. Through transmetalation reactions involving two aryloxides, mononuclear complexes of the type [M'(OArtBu)(2)Cl(THF)(2)] (M' = Sc (4), V (5), Cr (6), Ti (7)) can be prepared from the corresponding metal halide precursor MCl3(THF)(3). Additionally, two aryloxides can be coordinated to Ti(IV) via a protonolysis route of Ti(NMe2)(2)Cl-2 and 2 equiv of HOArtBu to yield [TKOArtBu)(2)Cl-2(NHMe2)] (8) in 72% isolated yield. Single-crystal X-ray diffraction studies of 1, 2, and the 3d metal complexes 5-8 clearly show the steric demand of the bulky ligand, whereas in transition metal complexes we do not observe the formation of mononuclear tris-aryloxide complexes.