Synthesis and Structural Characterization of β‐Diketiminato Yttrium Complexes and their Application in Epoxide/CO 2 ‐Copolymerization

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