The kinetics of formation of mono- and dicarbonyl complexes in two successive stages by direct carbonylation of ruthenium(II) chlorides in dimethylacetamide solution have been studied at 65–80° and up to 1 atm CO by gas uptake techniques. Both stages are first order in ruthenium. Formation of the monocarbonyl is independent of CO pressure; dicarbonyl formation is first order in CO at low pressures with the order decreasing towards zero with increasing pressure, and shows an inverse chloride dependence from 0.1–2.0 M added chloride. For both stages, the data are consistent with a mechanism involving predissociation. A similar mechanism is suggested for the corresponding reactions in 3 M HCl solution which had been studied earlier and which showed overall second-order kinetics.Discussion on the related formation of molecular nitrogen complexes of ruthenium(II) is presented.
