The photochemical carbonylation of benzene, and hydrogenation and hydrosilation of benzaldehyde catalyzed by ruthenium(O) complexes

The activation and functionalization of an arene C-H bond is achieved in the photochemical carbonylation of benzene catalyzed by the ruthenium-(O) complexes RuCl(CO)(NO)(PPh3)2, Ru(CO)3(PPh3)2 and Ru(CO)4(PPh3). Under the carbonylation conditions, both RuCl(CO)(NO)(PPh3)2 and Ru-(CO)3(PPh3)2 convert to Ru(CO)4(PPh3). The amount of benzaldehyde formed is limited by the unfavorable thermodynamics of the carbonylation reaction, C6H6 + CO → C6H5CHO, which has ΔG0298 of + 1.7 kcal mol−1. Both Ru(CO)3(PPh3)2 and Ru(CO)4(PPh3) catalyze the photochemical hydrogenation and hydrosilation of benzaldehyde as well. While coupling of either of these reactions with the carbonylation of benzene produces an overall reaction which is thermodynamically favorable, the use of CO/H2 and CO/-HSiEt3 mixtures does not dramatically improve the yield of benzene carbonylation products.