dOrbitalBeteiligung

dOrbitalBeteiligung is a term used in inorganic and coordination chemistry to describe the extent to which the d orbitals of a transition metal center participate in chemical bonding with ligands. In this sense, it captures the covalent contribution of metal d orbitals to the metal–ligand bond, complementing ionic descriptions of bonding. The concept is commonly discussed within molecular orbital theory and ligand-field theory to account for variations in bond character across complexes.

The degree of dOrbitalBeteiligung influences several properties of a compound. Higher d-orbital involvement generally increases covalency, enhances π-backbonding in ligand groups such as CO or CN−, and can alter ligand-field stabilization energy, color, magnetism, and reactivity. Factors that modulate participation include the identity and electronic demands of ligands, oxidation state of the metal, spin state, and overall geometry of the complex.

Assessment of dOrbitalBeteiligung relies on theoretical and experimental approaches. Computational methods such as density functional theory (DFT) and multireference calculations quantify the d-character of bonding orbitals and the degree of back-donation. Spectroscopic data (UV-Vis, infrared CO stretching frequencies), X-ray absorption, and analyses of bond lengths also provide indirect indicators of d-orbital involvement. Natural bond orbital analysis and other orbital-based metrics are sometimes used to articulate the contribution of d orbitals to specific bonds.

The term is most commonly encountered in discussions of transition-metal complexes and their bonding descriptions. It is sometimes used interchangeably with covalency of metal–ligand bonds, and may be contrasted with purely ionic models to emphasize the electronic nuance of d-orbital participation.