Characterization of Dimeric and Tetrameric μ‐Hydroxide Ytterbium(III) Binaphtholate Complexes

Abstract

Abstract Shibasaki’s heterobimetallic Lewis acids, M 3 (THF) n (BINOLate) 3 Ln (M=Li, Na, K and Ln=lanthanide), are an exceptionally useful class of asymmetric catalysts that exhibit high levels of enantioselectivity across a wide range of reactions. In many instances, it is necessary to add water (and base) to achieve maximum enantioselectivity. We have investigated the reaction of water with M 3 (THF) n (BINOLate) 3 Yb (M=Li, K) complexes and observed formation of a novel hydroxide‐bridged dimer (M=Li) and tetramer (M=K). These compounds have been characterized, including X‐ray structure analysis. Under anhydrous conditions, only 6‐coordinate monomeric Li 3 (THF) n (BINOLate) 3 Yb and K 3 (THF) n (BINOLate) 3 Yb complexes were isolated and characterized by X‐ray crystallography. Isolation of the dimer Li 4 (THF) 7 (BINOLate) 4 Yb 2 (μ‐OH) 2 and tetramer K 4 (THF) 9 (BINOLate) 6 Yb 4 (μ 3 ‐OH) 4 indicates that added water can react with this important class of bifunctional catalyst to give new products.