Ionic composite of palladium(II)/iron bis(dicarbollide) for catalytic oxidative carbonylation in the formation of diphenyl carbonate

Abstract

The carborane-based sandwich iron complex, [n-Bu4N]{Fe(3,3′)-[1,2-(PPh2)2-1,2-C2B9H9]2}, was synthesized in 53.1% yield. A catalyst composite of PdAc2/[n-Bu4N]{Fe(3,3′)-[1,2-(PPh2)2-1,2-C2B9H9]2} was found to be highly active for the oxidative carbonylation of phenol, with the formation of diphenyl carbonate (DPC). A DPC yield of 46% and a turnover number (TON) of 511 were achieved in 4 h using the composite at 110 °C. For comparison, the reaction was also investigated using catalyst composites of PdAc2/Mn(acac)3, PdAc2/Fe(acac)3, PdAc2/Co(acac)3 and PdAc2/Ce(acac)3 (acac = acetylacetone) under the same conditions of temperature and pressure. The DPC yield was determined by gas chromatography with flame ionization detector (GC-FID). All new products were characterized by elemental analysis, and by 1H, 13C, 11B and 31P NMR and FT-IR spectroscopy.