KINETICS OF THE WATER-GAS SHIFT REACTION CATALYZED BY CIS-[IR(CO)(2)(4-PIC)(2)]PF6 IN AQUEOUS 4-PICOLINE

Described is a kinetics study of the homogeneous water gas shift react ion catalyzed by the cis[Ir(CO)(2)(4-pic)(2)]PF6 complex in 4-picoline aqueous solution. The activity proved to be nonlinear in iridium tota l concentration, [Ir](tot), over the range 5 to 80 mM. This result was interpreted in terms of the presence of active mononuclear and polynu clear iridium species in the system, being the mononuclear the more ac tive. The rate displays a first order dependence on CO pressure, P(CO) , over the range 0.7 to 1.9 atm. The kinetics behavior with respect to P(CO) leads to propose the CO addition to the catalytic species prior to the rate-limiting step.