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

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Abstract
We assess the performance of density functional theory (DFT) and Møller–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(η5-Cp*)(η3-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, τHCTHhyb, ωB97X, and ωB97X-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 ωB97X-D (DFT plus an empirical molecular mechanics term) methods. This contrasts with an article in this Journal [Calhorda, M. J., Pregosin, P. S., and 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 ωB97X-D methods have both a smaller mean unsigned error than MP2 and the same maximum error. The M06, PW6B95, PBE0, M06-L, and ωB97X density functionals also have a smaller or the same mean unsigned error as MP2.

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