Rare-Earth-Metal Mixed Hydride/Aryloxide Complexes Bearing Mono(cyclopentadienyl) Ligands. Synthesis, CO2 Fixation, and Catalysis on Copolymerization of CO2 with Cyclohexene Oxide

Hydrogenolysis of mono(cyclopentadienyl)-ligated rare-earth-metal bis(alkyl) complexes Cp′Ln(CH2SiMe3)2(THF) (Ln = Y (1a), Dy (1b), Lu (1c); Cp′ = C5Me4SiMe3) with PhSiH3 afforded the mixed hydride/alkyl complexes [Cp′Ln(μ-H)(CH2SiMe3)(THF)]2 (Ln = Y (2a), Dy (2b), Lu (2c)). The overall structure of complexes 2a−c is a C2-symmetric dimer containing a planar symmetric Ln2H2 core at the center of the molecule. Deprotonation of ArOH (Ar = C6H2-tBu2-2,6-Me-4) by the metal alkyl group of 2a−c led to formation of the mixed hydride/aryloxide derivatives [Cp′Ln(μ-H)(OAr)]2 (Ln = Y (3a), Dy (3b), Lu (3c)), which adopt the dimeric structure through hydride bridges with trans-accommodated terminal aryloxide groups. Complexes 3a−c swiftly reacted with CO2 to generate the mixed formate/carbonate complexes [Cp′Ln(μ-η1:η1-O2CH)(μ-η1:η1-O2COAr)]2 (Ln = Y (4a), Dy (4b), Lu (4c)). The two Cp′Ln fragments in these complexes are bridged by the formate and carbonate species, respectively, to form two square-pyramidal geometri...