Rare Earth Complexes of Bulky 2,6-Diphenylphenolates Containing Additional, Potentially Buttressing 3,5-Substituents

The rare earth aryloxide complexes, [Yb(OArtBU)(3)-(THF)]. THF, [Sc(OArtBU)(3)(THF)]. THF, [Yb(OArMe)(3)(THF)], and [Sm(OArPh)(3)(THF)(2)] (OArR = 2,6-diphenyl-3,5-di-R-phenolate), have been prepared by redox transmetallation/ ligand exchange between the rare earth metal, bis(pentafluorophenyl)mercury, and HOArR in tetrahydrofuran. This reaction also provided [Yb(OArPh)(3)(DME)].3/2THF by incorporation of adventitious 1,2-dimethoxyethane. A similar reaction between Yb metal, diphenylmercury, and HOArMe gave [Yb(OArMe)(2)(THF)(3)]. The homoleptic complexes [Yb(OArPh)(3)] and [Sc(OArH)(3)] have been prepared by direct reaction of the rare earth element with HOArH in a sealed tube in the presence of mercury at elevated temperatures (200-250 degreesC) and the latter was converted into [Sc(OArH)(3)(THF)] by treatment with THF. X-ray crystal structure determinations of [Yb(OArtBU)(3)(THF)]. THF, [sc(OArtBu)(3)(THF)]. THF and [Yb(OArMe)(3)(THF)] show the complexes to be monomeric and four coordinate with a trigonal pyramidal stereochemistry. These structures provide clear evidence that groups meta to the phenolate donor can modify the coordination behaviour of the 2,6-diphenylphenolate ligand. In [Yb(OArPh)(3)(DME)].3/2THF a distorted square pyramidal stereochemistry is observed. The divalent complex [Yb(OArMe)(2)(THF)(3)] exhibits a distorted trigonal bipyramidal arrangement of the oxygen donor atoms with apical THF ligands. The homoleptic scandium 2,6-diphenylphenolate has three oxygen atoms in a triangular array with additional pi-eta (2)-Ph---Se interactions above and below the ScO3 plane [C-Sc-C = 154.2(8)degrees], providing a new type of binding of this aryloxide ligand.