Impact of Na− and K−C π-Interactions on the Structure and Binding of M₃(sol)_n(BINOLate)₃Ln Catalysts

Shibasaki's heterobimetallic complexes M₃(THF)_n(BINOLate)₃Ln [M = Li, Na, K; Ln = lanthanide(III)] are among the most successful asymmetric Lewis acid catalysts. Why does M₃(THF)_n(BINOLate)₃Ln readily bind substrates when M = Li but not when M = Na or K? Structural studies herein indicate Na− and K−C cation−π interactions and alkali metal radius may be more important than even lanthanide radius. Also reported is a novel polymeric [K₃(THF)₂(BINOLate)₃Yb]_n structure that provides the first evidence of interactions between M₃(THF)_n(BINOLate)₃Ln complexes.