175405-75-1Relevant academic research and scientific papers
Immobilization of Carbonylnickel Complexes: A Solid-State NMR Study
Behringer,Blümel
, p. 1814 - 1819 (1996)
Silica is commonly modified with bifunctional phosphines like PPh2CH2CH2Si(OEt)3 prior to immobilization of catalysts. Here, besides PPh2(CH2)3Si(OEt)3, ligands that are more stable toward oxidation, namely PPh2(C6H4)-Si(OEt)3, PPh2(C6H4)SiMe2(OEt), and PPh2(CH2)4OH, are applied. The di- and tricarbonylnickel complexes of these ligands are synthesized, characterized by 61Ni, 31P, 13C, and 1H NMR and IR spectroscopy, and immobilized on silica. Alternatively, the corresponding phosphine-modified silicas are treated with Ni(CO)4. The obtained materials are investigated by 31P and 13C solid-state NMR spectroscopy. Di- and tricarbonylnickel species can be distinguished by their different chemical shift anisotropies and also by their IR data. While the first route allows immobilization of both di- and tricarbonylnickel complexes, reaction of surface-bound phosphines with Ni(CO)4 gives the tricarbonyl species exclusively. Among the different ligands, PPh2(CH2)4OH has optimal qualities: It gives high surface coverages without oxidation or cross-linking, and therefore narrow NMR lines, and it allows 13C CP/MAS NMR spectroscopy.
