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

Various mixed methyl aryloxide complexes TptBu,MeLnMe(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 TptBu,MeLuMe2 and TptBu,MeYMe(AlMe4) via protonolysis with 1 or 2 equiv HOC6H2tBu2-2,6-Me-4 in n-hexane gave the desired complexes TptBu,MeLnMe(OAr). Corresponding treatment of TptBu,MeLuMe2 with the sterically less demanding HOC6H3Me2-2,6, HOC6H3iPr2-2,6 and HOC6H3(CF3)2-3,5 led to the formation of the bis(aryloxy) lutetium complexes TptBu,MeLu(OAr)2. Application of a salt-metathesis protocol employing TptBu,MeLnMe(AlMe4) and the potassium aryloxides KOAr made complexes TptBu,MeLnMe(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 Θ° of the [TptBu,Me] ancillary ligand. Treatmen...