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

✍ Scribed by Alfred J. Wooten; Luca Salvi; Patrick J. Carroll; Patrick J. Walsh

• Book ID: 101421785
• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 415 KB
• Volume: 349
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/adsc.200600600

✦ Synopsis

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.