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Creators/Authors contains: "Witzke, Ryan J."

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  1. Free, publicly-accessible full text available October 20, 2024
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  6. Abstract

    Anionic molecular models for nonhydrolyzed and partially hydrolyzed aluminum and gallium framework sites on silica, M[OSi(OtBu)3]4and HOM[OSi(OtBu)3]3(where M=Al or Ga), were synthesized from anionic chlorides Li{M[OSi(OtBu)3]3Cl} in salt metathesis reactions. Sequestration of lithium cations with [12]crown‐4 afforded charge‐separated ion pairs composed of monomeric anions M[OSi(OtBu)3]4with outer‐sphere [([12]crown‐4)2Li]+cations, and hydroxides {HOM[OSi(OtBu)3]3} with pendant [([12]crown‐4)Li]+cations. These molecular models were characterized by single‐crystal X‐ray diffraction, vibrational spectroscopy, mass spectrometry and NMR spectroscopy. Upon treatment of monomeric [([12]crown‐4)Li]{HOM[OSi(OtBu)3]3} complexes with benzyl alcohol, benzyloxide complexes were formed, modeling a possible pathway for the formation of active sites for Meerwin–Ponndorf–Verley (MPV) transfer hydrogenations with Al/Ga‐doped silica catalysts.

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