Kinetics and Mechanism of Substitution Reactions of η5-Cyclopentadienyldicarbonylrhodium(I) Derivatives. Rate Enhancement of Associative Substitution in Cyclopentadienylmetal Compounds

Article abstract of DOI:10.1021/ja00332a026

The reactions of Rh(η⁵-C9H7)(CO)2, Rh(η⁵-C9(CH3)7)(CO)2, Rh(η⁵-C5H4NO2)(CO)2, and 5-C5H4PPh3)(CO)2>⁺ with triphenylphosphine (PPh3) take place readily to form monosubstituted products.These reactions proceed solely by a second-order process, first order in the metal complex and first order in PPh3.The rates of reaction follow the order Rh(η⁵-C9H7)(CO)2 > Rh(η⁵-C9(CH3)7)(CO)2 > Rh(η⁵-C5H4NO2)(CO)2 > 5-C5H4PPh3)(CO)2>⁺, and all are orders of magnitude greater than that of Rh(η⁵-C5H5)(CO)2.The reasons for this ordering are discussed in terms of the presumed transition states of these reactions, relative to the corresponding reaction of Rh(η⁵-C5H5)(CO)2.