聚4-乙烯吡啶类高分子铑(I)化合物对甲醇羰化合成乙酸的催化性能

本文将聚4-乙烯吡啶(PVPy)、聚1-甲基-4-乙烯吡啶季铵碘(PVPyMe^+I^-)和4-乙烯吡啶/1-甲基-4-乙烯吡啶季铵碘共聚物P(VPy-VPyMe^+I^-)]分别与四羰基二氯二铑反应制备成高分子铑(I)催化剂, 并考察了它们各自在甲醇羰化反应中的催化行为。结合IR光谱对这些催化剂结构的分析研究表明, 以上4-乙烯吡啶类高分子链上所含的功能基各自与铑(I)配合物离子之间以不同的链联方式所产生的不同结构的活性物种对催化反应性能有着显著的影响, 具有双配位的螯合型稳定结构的Rh(I)/PVPy催化剂, 表现出较差的催化反应活性, 而离子键合型的Rh(I)/PVPyMe^+I^-和杂键合型的Rh(I)/P(VPy-VPyMe^+I^-)催化剂均表现较佳的反应性能, 特别是Rh(I)/P(VPy-VPyMe^+I^-),由于其形成具有更强亲核性的五配位中间过渡态参与反应过程, 从而在较大程度上提高了催化反应速率。

The catalytic properties of poly (4-vinylpyridine) bound Rh(I) complex for carbonylation of methanol to acetic acid

Polymer-immobilized Rh(I) complexes were prepared by the reaction of poly (4-vinylpyridine) (PVPy), poly (1-methyl-4-vinylpyridiumiodide) (PVPyMe^+I^-) and copoly (4-vinylpyridine/1-methyl-4-vinylpyridium iodide) P(VPy-VPyMe^+I^-) with Rh2 (CO)4Cl2, and their catalytic behaviors for the carbonylation of methanol to acetic aicd with CH3I as unique promotor was investigated. The IR studies of these catalysts indicated that the different active species produced by means of different bonding states between Rh(I) complex ions and functional groups in the above polymeric chains demonstrated a remarkable influence on the catalytic reactivities. The chelate-type catalyst with the double coordinations of two free base pyridine ligand groups to cis-dicarbonylrhodium, Rh(I)/PVPy, exhibited apparently a lower catalytic reactivity, while the ionically bound catalyst Rh(I)/PVPyMe^+I^- and the heterobound catalyst Rh(I)/P(VPy-VPyMe^+I^-) wre revealed to be of higher catalytic activities and selectivities under the same reaction conditions, in particular, the catalyst Rh(I)/P(VPy-VPyMe^+I^-) had the best rate enhancement for the catalytic carbonylation because of the formation of a five-coordinate intermediate which had a better nucleophilicity towards methyl iodide, and was found to be more active and favorable to the oxidative addition of the later.