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.