Synthesis And Characterization Of Bridged Phenolate Lanthanide Complexes And Their Reactivity

A series of lanthanide alkoxo and aryloxo complexes supported by carbon-bridged bis(phenolate) ligands were synthesized and structurally characterized. The catalytic activity of some of these complexes for the polymerization of L-lactide was tested, and the reactivity of homoleptic lanthanide bis(phenolate) complexes with some metal alkyls was studied. In addition, some lanthanide complexes supported by bridged tri(phenolate) ligands were synthesized and structurally characterized, and their reactivity was studied. The cabon-bridged bis(phenolato) ligand used is CH2(4-Me-6-tBu-C6H2O)2, abbreviated as MBMP, the bridged tri(phenolate) ligand is N,N,N'-tris-(3,5-di-tert-butyl-2-hydroxybenzyl)- benzene-1,2-diamine,abbreviated as L.1. Reactions of Cp3La(THF) with MBMPH2 in a 1:1 molar ratio in THF at 50oC for about 2 h, then with 1 equiv. of 2,2,2-trifluoroethanol, benzylic alcohol or N,N-dimethylamidoethanol, gave the neutral bis(phenolate) lanthanide alkoxides [(MBMP)La(μ-OCH2CF3)(THF)2]2 (1), [(MBMP)La(μ-OCH2Ph)(THF)2]2 (2) and [(MBMP)La(μ-OCH2CH2NMe2)(THF)2]2 (3),the intermediate (MBMP)La(THF)3 (4) of the reaction was separated and characterized. Complexes 1-4 were characterized by IR and elemental analysis. The definitive molecular structures of 2 and 4 were confirmed by single crystal X-ray diffraction.2. Complexes 1-3 can be used as single component catalysts to initiate the ring-opening polymerization of L-lactide with good activity. It was found that complex 1 initiated the polymerization in a controlled manner.3. Reactions of Cp3La(THF) with MBMPH2 in a 1:1 molar ratio in THF at 50oC for about 2 h, then with 1 equiv. of p-CH3O-C6H4OH, p-tBu-C6H4OH or 2,6-tBu2-4-Me-C6H2OH, gave the neutral bis(phenolate) lanthanide aryloxides [(MBMP)Ln(OC6H4-4-OCH3)(THF)2]2 (Ln = Sm (5), La (6)), (MBMP)La(O C6H4-4-tBu)(DME)2, (7) and (MBMP)La(OC6H2-2,6-tBu2-4-Me)(THF)2 (8). Complexes 5-8 were characterized by IR and elemental analysis. The definitive structures of 5 and 7 were confirmed by single crystal X-ray diffraction.4. The lanthanide aryloxides supported by carbon-bridged bis(phenolate) ligands could initiate the ring-opening polymerization of L-lactide with good activity. It was found that the bulkiness of the substitution groups on the arene rings of the aryloxo groups has significant effect on the catalytic activity.5. Reactions of Cp3Yb(THF) with MBMPH2 in a 1:2 molar ratio in toluene at 80oC for about 20 h, gave the neutral homoleptic complex (MBMP)Yb(MBMP-H)(THF)2 (10), the intermediate (MBMP)Yb(THF)2(9) of the reaction was separated and characterized. Reaction of complex 10 and (MBMP)Y(MBMP-H)(THF)2 with ZnEt2 in a 1:1 molar ratio in toluene at 80oC for about 20 h, respectively, gave the ligand redistributed product [(μ-MBMP)Zn(THF)]2 (11). Similarly, reaction of complex 10 with 1 equiv of AlEt3 in toluene at room temperature afforded the unexpected ligand redistributed products, and a novel discrete ion pair ytterbium complex [(MBMP)Yb(THF)2(DME)][(MBMP)2Yb(THF)2] (12) was isolated. Reaction of compex 9 with 1 equiv of H2O in THF at -78oC afforded hydrolysate [(MBMP)Yb(μ-OH)(THF)2]2 (13). Complexes 9-13 were characterized by IR and elemental analysis and single crystal X-ray diffraction.6. Reactions of Cp3Ln(THF) with LH3 in a 1:1 molar ratio in THF at room temperature for about 12 h, after workup, gave the neutral complexes LLn(DME)2 (Ln = Y (14), Eu (15), Tb (16)). Reaction of complex 14 with n-BuLi in a 1:1 molar ratio in THF at -78oC afforded complex [LY]2Li2O (17) Complexes 14-17 were characterized by IR, elemental analysis and single crystal X-ray diffraction.