Geometries of Second-Row Transition-Metal Complexes\nfrom Density-Functional Theory

Abstract

A data set of 19 second-row transition-metal complexes has been collated from\nsufficiently precise gas-phase electron-diffraction experiments and used for evaluating errors in\nDFT optimized geometries. Equilibrium geometries have been computed using 15 different\ncombinations of exchange-correlation functionals in conjunction with up to three different effective\ncore potentials. Most DFT levels beyond the local density approximation can reproduce the 29\nmetal−ligand bond distances selected in this set with reasonable accuracy and precision, as\nassessed by the mean and standard deviations of optimized vs experimentally observed bond\nlengths. The pure GGAs tested in this study all have larger standard deviations than their\ncorresponding hybrid variants. In contrast to previous findings for first-row transition-metal\ncomplexes, the TPSSh hybrid meta-GGA is slightly inferior to the best hybrid GGAs. The ranking\nof some popular density functionals, for second-row transition-metal complexes, ordered\naccording to decreasing standard deviation, is VSXC ≈ LSDA > BLYP > BP86 > B3LYP ≈\nTPSSh > PBE hybrid ≈ B3PW91 ≈ B3P86. When zero-point vibrational corrections, computed\nat the BP86/SDD level, are added to equilibrium bond distances obtained from a number of\ndensity-functional/basis-set combinations, the overall performance in terms of mean and standard\ndeviations from experiment is not improved. For a combined data set comprised of the first-\nand second-row transition-metal complexes the hybrid functionals B3P86, B3PW91, and the\nmeta-GGA hybrid TPSSh afford the lowest standard deviations.