Kinetics study of the substitution reaction of fac-[FeII(CN)2(CO)3I]− with PPh3

Abstract Substitution reaction of fac -[Fe II (CN) 2 (CO) 3 I] − with triphenylphosphine (PPh 3 ) produced mono phosphine substituted complex cis - cis -[Fe II (CN) 2 (CO) 2 (PPh 3 )I] − . Crystal structure of the product showed that carbonyl positioned trans - to iodide was replaced by PPh 3 . The substitution reaction was monitored by quantitative infrared spectroscopic method, and the rate law for the substitution reaction was determined to be rate =  k [[Fe II (CN) 2 (CO) 2 (PPh 3 )I] − ][PPh 3 ]. Transition state enthalpy and entropy changes were obtained from Eyring equation k  = ( k B T / h )exp(−Δ H ≠ / RT  + Δ S ≠ / R ) with Δ H ≠  = 119(4) kJ mol −1 and Δ S ≠  = 102(10) J mol −1  K −1 . Positive transition state entropy change suggests that the substitution reaction went through a dissociative pathway.