Kinetic studies and mechanism of triiron dodecacarbonyl reactions : I. Nucleophilic substitution in triiron dodecacarbonyl by triphenylphosphine in benzene

The kinetics of the reaction of triiron dodecacarbonyl with triphenylphosphine has been studied at various temperatures and different concentrations. It is a first order reaction with respect to Fe₃(CO)₁₂. P(C₆H₅)₃ reacts with Fe₃(CO)₁₂ according to the expression K_obsd = K[Fe₃(CO)₁₂] + K[P(C₆H₅)₃]/ [Fe₃(CO)₁₂]. Up to a certain ratio of P(C₆H₅)₃ to Fe₃(CO)₁₂ (approx. 10/1), after which K_obsd deviates from the above expression. K_obsd also depends upon the concentrations of both the reactants. An induction period is always observed which decreases with increase in temperature. Thermodynamic parameters for the reaction have also been calculated.