The solution structures of the ytterbium heterobimetallic complexes Na3[Yb((S)-BINOL)3] (1), K3[Yb((S)-BINOL)3] (2), and Li3[Yb((S)-BINOL)3] (3), belonging to a family of well-known enantioselective catalysts, are studied by means of NMR and circular dichroism (CD) in the UV and near-IR regions. The experimental NMR paramagnetic shifts were employed to obtain a refined solution structure of 1. NMR analysis demonstrated that 1, 2, and 3 have the same solution geometry but different magnetic susceptibility anisotropy factors. By comparing XRD and NMR structures of 1, we demonstrate that, upon dissolution, this complex experiences a rearrangement from the crystalline C3 symmetry into the solution D3 symmetry. Remarkably, Yb is not bound to water in solution, and Ln−BINOL bonds are labile as demonstrated through EXSY. NIR−CD is confirmed especially sensitive to changes in the ytterbium coordination sphere.
|Autori:||DI BARI L; LELLI M; PINTACUDA G.; PESCITELLI G; MARCHETTI F; SALVADORI P|
|Titolo:||Solution versus Solid-State Structure of Ytterbium Heterobimetallic Catalysts|
|Anno del prodotto:||2003|
|Digital Object Identifier (DOI):||10.1021/ja0297640|
|Appare nelle tipologie:||1.1 Articolo in rivista|