Rare earth metal bis(alkyl) complexes bearing amino phosphine ligands: Synthesis and catalytic activity toward ethylene polymerization

Abstract

Reactions of neutral amino phosphine compounds HL 1–3 with rare earth metal tris(alkyl)s, Ln(CH 2SiMe 3) 3(THF) 2, afforded a new family of organolanthanide complexes, the molecular structures of which are strongly dependent on the ligand framework. Alkane elimination reactions between 2-(CH 3NH)-C 6H 4P(Ph) 2 (HL 1) and Lu(CH 2SiMe 3) 3(THF) 2 at room temperature for 3 h generated mono(alkyl) complex (L 1) 2Lu(CH 2SiMe 3)(THF) ( 1). Similarly, treatment of 2-(C 6H 5CH 2NH)-C 6H 4P(Ph) 2 (HL 2) with Lu(CH 2SiMe 3) 3(THF) 2 afforded (L 2) 2Lu(CH 2SiMe 3)(THF) ( 2), selectively, which gradually deproportionated to a homoleptic complex (L 2) 3Lu ( 3) at room temperature within a week. Strikingly, under the same condition, 2-(2,6-Me 2C 6H 3NH)-C 6H 4P(Ph) 2 (HL 3) swiftly reacted with Ln(CH 2SiMe 3) 3(THF) 2 at room temperature for 3 h to yield the corresponding lanthanide bis(alkyl) complexes L 3Ln(CH 2SiMe 3) 2(THF) n ( 4a: Ln = Y, n = 2; 4b: Ln = Sc, n = 1; 4c: Ln = Lu, n = 1; 4d: Ln = Yb, n = 1; 4e: Ln = Tm, n = 1) in high yields. All complexes have been well defined and the molecular structures of complexes 1, 2, 3 and 4b– e were confirmed by X-ray diffraction analysis. The scandium bis(alkyl) complex activated by AlEt 3 and [Ph 3C][B(C 6F 5) 4], was able to catalyze the polymerization of ethylene to afford linear polyethylene.