Synthesis and structural characterization of β-diketiminato yttrium complexes and their application in Epoxide/CO2-Copolymerization

The beta-diketiminato yttrium complexes [(BDIPh)(2)Y-{N(SiHMe2)(2)}] (1, BDIPh = [PhNC(Me)CHC(Me)NPh](-)), [(BDIPh)(3)Y] (2), and [(C5Me5)(BDIPh)Y{N(SiHMe2)(2)}] (4) are available via amine elimination starting from (BDIPh)H and either [Y{N(SiHMe2)(2)}(3)(THF)(2)] or [(C5Me5)Y{N(SiHMe2)(2)}(2)(THF)] (3). X-ray crystallographic analysis of complexes 1 and 4 revealed a eta(5) coordination mode for the beta-diketiminato ligand, whereas the distorted octahedral complex 2 displayed pure K 2 coordination. Complex 3 was also structurally characterized. 1, 3, and 4 are moderately active catalysts in the copolymerization of cyclohexene oxide and CO2. Complex 3 was the most active system (TOF up to 33 h(-1) at 75 degrees C, 8.5 atm CO2) and gave the highest molecular weight and narrowest polydispersity (M-n = 12600 g mol(-1), M-n/M-n = 1.6).