CONTROVERSIAL EXOTHERMICITY OF THE OXIDATIVE ADDITION OF METHANE TO (CYCLOPENTADIENYL)RHODIUM CARBONYL

A wide range of values for the exothermicity of the oxidative addition of methane to (cyclopentadienyl)rhodium carbonyl have been reported a t the MP2 level of theory. These energies are recalculated using sever al different basis sets which reproduce previous results and provide e vidence for the inadequacy of some commonly used basis sets. The calcu lations show that the magnitude of the exothermicity of this reaction is particularly sensitive to the metal 5s orbital. With a metal basis set which includes proper representation of the (n + I)s and -p metal orbitals, the exothermicity is also calculated at the MP3, MP4(SDQ), a nd QCISD levels. The best results show that the MPX perturbation serie s does not converge well and that the MP2 results in any basis set are only qualitative.