Immobilization of Bisphosphinoamine Linkers on Silica: Identification of Previously Unrecognized Byproducts via 31P CP/MAS and Suspension HR-MAS Studies
نویسندگان
چکیده
A new bisphosphinoamine linker with ethoxysilyl group has been synthesized and applied for anchoring nickel catalysts to alumina and silica. Side reactions occurred, and the reactions of various bisphosphinoamine ligands with silica were studied by 31P CP/MAS and suspension HR-MAS NMR. Besides the desired immobilization, two main side reactions have been found. The phosphine moieties of the linkers can be quaternized by ethyl groups from the ethoxysilyl functions. Furthermore, the bisphosphinoamine group can rearrange to the corresponding phosphinimine unit that is subsequently hydrolyzed, resulting in the amine and tetraphenyldiphosphine oxide. The latter is bound firmly to the silica surface.
منابع مشابه
Immobilization of phosphines on silica: identification of byproducts via 31P CP/MAS studies of model alkyl-, aryl-, and ethoxyphosphonium salts.
Immobilizing bifunctional phosphines with ethoxysilane groups on silica often leads predominantly, and sometimes quantitatively, to P(V) side products that occupy space on the surface but cannot bind metal complexes. Although this side reaction is well-known, and dreaded because it leads to leaching of adsorbed catalysts that are not bound covalently, the exact nature of the surface-bound side ...
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