-, -, and bimetallic clusters as catalysts for carbonylation of nitrobenzene to methyl phenylcarbamate

Article abstract of DOI:10.1016/0022-328X(92)83101-M

Bimetallic clusters of the general formula 2 (M = Fe, Ru, or Os; PPN^- = (PPh3)2N⁺) are active catlysts in the presence of methanol for the carbonylation of nitrobenzene to methyl phenylcarbamate.The clusters are active even without co-catalyst, but the addition of bipy (2,2'-bipyridine) greatly enhances both rates and selectivities.In the absence of methanol the conversion was much lower, with a low selectivity in phenyl isocyanate.Interchanging Fe, Ru, and Os has a negligible effect on the activity and a moderate effect on the selectivity, with ruthenium being best.However, the monometallic rhodium cluster ^- proved to be both more active and selective, and the monomer ^- was found to be even better.This last catalytic system has been optimized with respect to temperature, CO pressure and the bipy/Rh ratio.The influence of solvent was also examined.