- Kinetic and mechanistic studies of phosphorus ligand exchange reactions of trans-(C6H5)3PFe(CO)3C(OC2H5)R (R = CH3 and C6H5) with L (L = P(n-C4H9)3, P(OC6H5)3, and P(C6H11)3) to form trans-LFe(CO)3C(OC2H5)R compounds are reported. The rates of these substitution reactions are independent of the nature and concentration of the incoming ligands (L) and proceed according to the rate expression: rate = k1 [(C6H5)3PFe(CO)3C(OC2H5)R]. These reaction rates are dependent upon the nature of the carbene ligand with C(OC2H5)C6H5 labilizing the frans-phosphine ligand more strongly than C(OC2H5)CH3. Competitive reactions for the intermediate [Fe(CO)3C(OC2H5)CH3] have been investigated for a number of ligands. The [Fe(CO)3C(OC2H5)CH3] intermediate reacts with various phosphorus ligands at different rates and shows a preference for more nucleophilic reagents. Equilibrium constant measurements for the reaction (C6H5)3 PFe(CO)3 C(O-C2H5)CH3 + L LFe(CO)3C(OC2H5)CH3 + P(C6H5)3 are also reported. 1974, American Chemical Society. All rights reserved.