How Much Electron Donation Is There In Transition Metal Complexes? A Computational Study

• Published in: Journal of chemical theory and computation Vol. 20; no. 12; pp. 4965 - 4976
• Main Authors: Obeng, Augustine, Autschbach, Jochen
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25.06.2024
• Subjects: Coordination compounds; Density functional theory; Errors; Ligands; Transition metal compounds
• ISSN: 1549-9618; 1549-9626; 1549-9626
• DOI: 10.1021/acs.jctc.4c00404

The “dative” covalent interactions between metals and ligands in coordination compounds, i.e., metal-to-ligand and ligand-to-metal donation, are manifestations of electron delocalization and subject to errors in approximate calculations. This work addresses the extent of dative bonding/donation in a series of closed-shell transition metal complexes. Several Kohn–Sham density functionals, representing different “rungs” of approximations, along with post-Hartree–Fock methods are assessed in comparison to CCSD­(T). Two widely used nonhybrid and global hybrid density functionals (B3LYP, PBE0) tend to produce notably too strong donation. Global hybrids with elevated fractions of exact exchange (40 to 50%) and the range-separated exchange functional CAM-B3LYP tend to perform better for the description of the donation. The performance of a double-hybrid functional is found to be quite satisfactory, correcting errors seen in MP2 calculations. A fast approximate coupled-cluster model (DLPNO-CCSD) also gives a reasonable description of the donation, with a tendency to underestimate its extent.