THE CATALYTIC PROPERTIES OF POLY(4-VINYLP YRIDINE) BOUND RH(I) COMPLEX FOR CARBONYLATION OF METHANOL TO ACETIC-ACID

Polymer-immobilized Rh(I) complexes were prepared by the reaction of p oly(4-vinylpyridine) (PVPy), poly(1-methyl-4-vinylpyridium iodide) (PV PyMe+ I-) and copoly (4-vinylpyridine/1-methyl-4-vinylpyridium iodide) [P(VPy-VPyMe+ I-)] with Rh-2(CO)(4)Cl-2, and their catalytic behavior s for the carbonylation of methanal to acetic acid with CH3I as unique promotor was investigated. The IR studies of the catalysts indicated that the different active species produced by means of different bondi ng states between Rh(I) complex ions and functional groups in the abov e polymeric chains demonstrated a remarkable influence on the catalyti c reactivities. The chelate-type catalyst with the double coordination s of two free base pyridine ligand groups to cis-dicarbonyl rhodium, R h(I)/PVPy, exhibited apparently a lower catalytic reactivity, while th e ionically hound catalyst Rh(I)/PVPyMe+ I- and the hetero-bound catal yst Rh(I)/P(VPy-VPyMe+ I-) were revealed to be of higher catalytic act ivities and selectivities under the same reaction conditions. in parti cular, the catalyst Rh(I)/P(VPy-VPyMe+ I-) had the best rate enhanceme nt for the catalytic carbonylation because of the formation of a five- coordinate intermediate which had a better nucleophilicity towards met hyl iodide, and was found to be more active and favorable to the oxida tive addition of the later.