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)2Cl(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)2Cl2 and 2 equiv of HOArtBu to yield [Ti(OArtBu)2Cl2(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.