Immobilization of phosphines on silica: identification of byproducts via 31P CP/MAS studies of model alkyl-, aryl-, and ethoxyphosphonium salts.
Immobilization of phosphines on silica: identification of byproducts via 31P CP/MAS studies of model alkyl-, aryl-, and ethoxyphosphonium salts.
复制标题
二氧化硅上膦的固定化：通过模型烷基、芳基和乙氧基鏻盐的 31P CP/MAS 研究鉴定副产物。
DOI：
10.1021/ic049065j
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发表时间：
2004
影响因子：
4.6
通讯作者：
J. Blümel
中科院分区：
文献类型：
--
作者：
J. Sommer;Y. Yang;D. Rambow;J. Blümel
在二氧化硅上用乙氧基硅烷基团固定双功能膦通常会导致P(V)副产物占据表面空间，但不能结合金属配合物。虽然这种副反应是众所周知的，并且令人恐惧，因为它会导致未共价结合的吸附催化剂的浸出，但表面结合的副反应的确切性质尚不清楚。借助于[R3PEt]+X-和[R3POEt]+X- （R=烷基，芳基；X=Cl-, Br-, I-, BF4-）的多晶模型化合物及其固体核磁共振特征[δ (31P), CSA]，证明了副产物是由硅氧阴离子[R3PEt]+[Si-O]-结合在表面的乙基磷盐。
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 product was not yet known. With the help of polycrystalline model compounds of the types [R3PEt]+X- and [R3POEt]+X- (R=alkyl, aryl; X=Cl-, Br-, I-, BF4-) and their solid-state NMR characteristics [delta(31P), CSA], it is demonstrated that the side product is an ethylphosphonium salt bound to the surface by a siloxide anion, [R3PEt]+[Si-O]-.