Kinetic and spectroscopic studies of the substitution reactions of [Rh(acac)(CO)2] with triphenylphosphite

Summary The substitution reactions of [Rh(acac)(CO)₂] with triphenylphosphite (P) to produce [Rh(acac)(CO)P], [Rh(acac)P₂] and [PhP₃P], were studied in detail using spectroscopic (n.m.r., i.r. and u.v.-vis.) and kinetic techniques. The kinetic data demonstrate that the first substitution process is very fast and followed by the rate-determining second step. The subsequent loss of acac is relatively slow. The activation enthalpy for the formation of [Rh(acac)P₂] is extremely low and possibly accounts for the catalytic nature of this system in hydrogenation and hydroformylation reactions.