Performance of DFT and MP2 Approaches for Geometry of Rhenium Allenylidenes Complexes and the Thermodynamics of Phosphines Addition

The performance of density functional theory (DFT) and Møller-Plesset perturbation second order theory (MP2) for prediction of the geometry of an important class of rhenium complexes and the thermodynamics of their reaction with nucleophiles has been assessed. In particular, we addressed the rhenium(I) allenylidene [(triphos)(CO)2Re(=C=C=CPh2)] +  species [triphos = MeC(CH2PPh2)3] and its reaction toward tertiary phosphines. Several exchange-correlation functionals were tested and the results indicate that the usually employed GGA and hybrid functionals, such a BP86, BLYP, B3LYP and PBE while correctly predicting the geometry of these species, qualitatively and quantitatively fail to reproduce the thermodynamics for the addition of the phosphine nucleophiles, especially the first three ones, with errors up to 30 kcal mol− 1. Reasonable results, qualitatively in agreement with experimental evidence, can be obtained only through the use of a correlated wavefunction approach such as MP2 or of the more recently developed functionals M06 and M06-L.