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Download fileSolution versus Solid-State Structure of Ytterbium Heterobimetallic Catalysts
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posted on 2003-04-15, 00:00 authored by Lorenzo Di Bari, Moreno Lelli, Guido Pintacuda, Gennaro Pescitelli, Fabio Marchetti, Piero SalvadoriThe 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 đ 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 LnâBINOL bonds are labile as
demonstrated through EXSY. NIRâCD is confirmed especially sensitive to changes in the ytterbium
coordination sphere.
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susceptibility anisotropy đ factorsytterbium coordination sphereEXSYLi 3NMR analysisYbytterbium heterobimetallic complexes Na 3solution D 3 symmetryNMR structuresXRDC 3 symmetrysolution structureNIRsolution geometryenantioselective catalystsYtterbium Heterobimetallic CatalystsUVsolution structuresBINOL