Mixed Methyl Aryloxy Rare-Earth-Metal Complexes Stabilized by a Superbulky Tris(pyrazolyl)borato Ligand

Various mixed methyl aryloxide complexes Tp(tBu)'(Me)LnMe(OAr) (Ln = Y, Lu) were obtained in moderate to high yields according to distinct synthesis protocols dependent on the metal size and sterics of the phenolic proligand. The reaction of Tp(tBu,Me)LuMe(2) and Tp(tBu,Me)YMe(AlMe4) via protonolysis with 1 or 2 equiv HOC(6)H(2)tBu(2)-2,6-Me-4 in n-hexane gave the desired complexes Tp(tBu,Me)LnMe(OAr). Corresponding treatment of Tp(tBu,Me)LuMe(2) with the sterically less demanding HOC6H3Me2-2,6, HOC(6)H(3)iPr(2)-2,6 and HOC6H3(CF3)(2)-3,5 led to .- u the formation of the bis(aryloxy) lutetium complexes Tp(tBu,Me)Lu( OAr)(2). Application of a salt-metathesis protocol employing Tp(tBu)'(Me)LnMe(AlMe4) and the potassium aryloxides KOAr made complexes Tp(tBu)'(Me)LnMe(OAr) accessible for the smaller aryloxy ligands as well. All complexes were analyzed by X-ray crystallography to compare the terminal Ln-Me bond lengths and to evaluate the implication of the methyl/aryloxy coordination for the exact cone angles Theta degrees of the [Tp(tBu,Me)] ancillary ligand. Treatment of Tp(tBu)'(Me)LnMe(AlMe4) (Ln = Lu, Y) with HOC(6)H(2)tBu(2)-2,6-Me-4 in the presence of 4-(dimethylamino)pyridine (dmap) produced ion-separated complexes [Tp(tBu)'(Me)LnMe(dmap)(2)][Me(3)AlOC(6)H(2)tBu(2)-2,6-Me-4)]. The thermal instability of Tp(tBu)'(LuMe)-Lu-Me(OC(6)H(2)tBu(2)-2,6-Me-4) was revealed by the formation of (Tp((t)(Bu)(-H)/(tBu)2,Me))Lu(OC(6)H(2)tBu(2)-2,6-Me-4) via intramolecular C-H-bond activation.