Modelling the reduction of nitrobenzene with [Ru3(CO)12] as a homogeneous catalyst. X-Ray structures of [Ru3H(CO)10(PhNH)] and [N(PPh3)2][Ru3H(CO)9(PhN)

Abstract

The ability of [Ru3(CO)12] to act as a homogeneous catalyst in the reductive carbonylation of nitrobenzene has been confirmed. Under the conditions used in the catalytic runs the reactivities of the six clusters [Ru3(CO)10(µ3-PhN)](1), [Ru3H(CO)10(PhNH)](2), [Ru3H2(CO)9(µ3-PhN)](3), [Ru3H(CO)9(µ3-PhNCO)]–(4), [Ru3H(CO)9(µ3-PhN)]–(5), and [Ru3(CO)10(µ-PhNCHO)]–(6) are described. The syntheses of (4)–(6) and the X-ray structures of (2) and (5a), the [N(PPh3)2]+ salt of (5), are also discussed. The conversion of complex (4) into (5) has been studied kinetically. The activation parameters and a Hammett correlation for this reaction are reported. From the observed reactivities of (1)–(6), two model catalytic cycles for catalytic systems with or without OR–(R = H or Me) as promoters have been proposed. Clusters (4) and (6) are probable catalytic intermediates in RO–-promoted catalytic runs.