Modeling Transition Metal Reactions with Range-Separated Functionals.

The performance of range-separated functionals for the calculation of reaction profiles of organometallic compounds is considered. Sets of high-level computational results are used as reference data for the most part. The benchmark data include a number of reactions involving small molecules reacting with the Pd atom, PdCl(-), PdCl2, and a Ni atom, the reaction of a model Grubbs catalyst, and the ligand binding in a real Grubbs catalyst. Range-separated functionals are found to improve upon most standard local functionals especially if an optimized range-separation parameter is used. They do not represent an improvement upon the better-performed global hybrid functionals or a local functional that includes a larger number of adjustable parameters. Some unusual results for molecule-molecule interaction energies are observed and explained by a detailed analysis of the contributions to the bonding energies. The influence of range separation on the barriers and reaction energies is also investigated.