Evidence for Substrate Binding by the Lanthanide Centers in [Li3(thf)n(binolate)3Ln]: Solution and Solid-State Characterization of Seven- and Eight-Coordinate [Li3(sol)n(binolate)3Ln(S)m] Adducts

摘要

The heterobimetallic [M3(thf)n(binolate)3Ln] (binol=1,1-bi-2-naphthol; M=Li, Na, K; thf=tetrahydrofuran) catalysts (Figure 1) developed by Shibasaki and co-workers have proven to be among the most versatile and successful asymmetric Lewis acid catalysts introduced to date.[1]-[3] Central to mechanistic proposals involving [M3(thf)n(binolate)3Ln] heterobimetallic compounds is Lewis acid activation of the substrate by the lanthanide.[2]-[4] Prior efforts to detect lanthanide-substrate interactions, however, have not been successful. Herein, we disclose solid-state and solution evidence that [Li3(thf)n(binolate)3Ln] catalysts can bind organic substrates and substrate analogues to form seven- and eight-coordinate Ln centers.