3d Early
Transition Metal Complexes Supported by a
New Sterically Demanding Aryloxide Ligand
- Publication date
- Publisher
Abstract
The
bulky aryloxide 2,6-bis(diphenylmethyl)-4-<i>tert</i>-butylphenol
[HOAr<sup>tBu</sup>] (<b>1</b>) can be synthesized
from 4-<i>tert</i>-butylphenol and benzhydrol in solvent-free
conditions and obtained pure in 91% yield. Deprotonation of HOAr<sup>tBu</sup> is accomplished with M(N(SiMe<sub>3</sub>)<sub>2</sub>)
(M = Na, Li), yielding the corresponding salts of the aryloxide [MOAr<sup>tBu</sup>] (M<sup>+</sup> = Na (<b>2</b>), Li(<b>3</b>)) 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′(OAr<sup>tBu</sup>)<sub>2</sub>Cl(THF)<sub>2</sub>] (M′ = Sc (<b>4</b>), V (<b>5</b>), Cr (<b>6</b>), Ti (<b>7</b>)) can be prepared
from the corresponding metal halide precursor MCl<sub>3</sub>(THF)<sub>3</sub>. Additionally, two aryloxides can be coordinated to Ti(IV)
via a protonolysis route of Ti(NMe<sub>2</sub>)<sub>2</sub>Cl<sub>2</sub> and 2 equiv of HOAr<sup>tBu</sup> to yield [Ti(OAr<sup>tBu</sup>)<sub>2</sub>Cl<sub>2</sub>(NHMe<sub>2</sub>)] (<b>8</b>)
in 72% isolated yield. Single-crystal X-ray diffraction studies of <b>1</b>,<b> 2</b>, and the 3d metal complexes <b>5</b>–<b>8</b> 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
