Performance of Density Functional Theory and Moller-Plesset Second-Order Perturbation Theory for Structural Parameters in Complexes of Ru

We assess the performance of density functional theory (DFT) and Moller-Plesset second-order perturbation theory (MP2) for predicting structural parameters in Ru complexes, in particular, a Ru(IV) allyl dicationic complex with the formula [Ru(eta(5)-Cp*)(eta(3)-CH2CHCHC6H5)(NCCH3)(2)](2+) and the molecules RuO4 and Ru(C2O4)(2)(H2O)(2)(-), where Cp* denotes C5Me5 and Me denotes methyl. The density functionals studied are B3LYP, B3PW91, M05, M06, M06-L, MOHLYP, MPW3LYP, PBE0, PW6B95, SOGGA, tau HCTHhyb, omega B97X, and omega B97X-D, in combination with three different basis sets, namely, LANL2DZ, def2-SVP, and def2-TZVP. The theoretically computed Ru-C distances corresponding to the phenylallyl complex are especially well predicted by the SOGGA (pure DFT) and omega B97X-D (DFT plus an empirical molecular mechanics term) methods. This contrasts with an article in this Journal [Calhorda, M. J.; Pregosin, P. S.; Veiros, L. F. J. Chem. Theory Comput. 2007, 3, 665-670] in which it was found that DFT cannot account for these Ru-C distances. Averaging over four Ru-C distances in the allyl complex and three unique Ru-O distances in RuO4 and Ru(C2O4)(2)(H2O)(2)(-), the SOGGA and omega B97X-D methods have both a smaller mean unsigned error than MP2 and the same maximum error. The M06, PW6B95, PBE0, M06-L, and omega B97X density functionals also have a smaller or the same mean unsigned error as MP2.