Hovedliganden

Hovedliganden are ligands that occupy the primary coordination sphere of a metal center in coordination chemistry. They form bonds with the central metal and define the main geometry and electronic properties of a complex. The term is used in Scandinavian literature and translates to “main ligands” or “primary ligands” in English.

These ligands can be monodentate or polydentate and are distinguished from secondary ligands, counterions, or solvent molecules that are not bound in the first coordination sphere. The nature and denticity of hovedliganden determine the coordination number, ligand field strength, and the stability of the complex. They influence properties such as geometry (octahedral, square planar, tetrahedral), color, and reactivity. Chelating hovedliganden often confer greater stability due to the chelate effect.

Common examples include ammonia, water, cyanide, carbon monoxide, ethylenediamine, and bipyridine when coordinated to metals such as iron, copper, or nickel. The arrangement of hovedliganden around the metal center governs electronic structure and catalytic potential, as well as kinetic lability or inertness of the complex.

Usage context: In English-language texts, the concept is usually described as primary ligands or first-sphere ligands. The idea is central to ligand design, catalysis, and inorganic synthesis, where selecting appropriate hovedliganden alters reactivity, catalytic pathways, and redox behavior.