komplexisid

Komplexisid are a concept in chemistry referring to coordination complexes, structures in which a central metal atom or ion is surrounded by ligands that donate electron pairs to form coordinate covalent bonds. The ligands create a coordination sphere around the metal center, and the properties of the complex depend on both the metal and the ligands. In these complexes the metal is typically a transition metal; common oxidation states vary, and the ligands may be neutral molecules (like ammonia) or anions (like chloride). The arrangement results in a defined coordination number, such as 4 or 6, reflecting the number of donor atoms bound to the metal.

Classification and structure: Mononuclear complexes have a single metal center, while polynuclear complexes have two or more metals linked by bridging ligands. Geometric types include octahedral, tetrahedral, and square planar. Denticity describes the number of donor sites per ligand (monodentate, bidentate, etc.). Properties such as color, magnetism, and stability arise from ligand field effects and the electronic structure of the metal. Colors often originate from d-d transitions or charge-transfer transitions, and stability is described by formation constants that influence reactivity in catalysis or biological processes.

Formation and examples: Formation typically involves combining a metal salt with suitable ligands under controlled conditions; complexes can be labile or inert depending on kinetics and ligand strength. Notable examples include [Cu(NH3)4]2+, [Fe(CN)6]3-, and the heme iron complex in hemoglobin.

Applications: The field spans catalysis, materials science, and bioinorganic chemistry, including homogeneous catalysis, dye chemistry, and metal-organic frameworks that incorporate coordination polymers.

See also: coordination chemistry, ligands, chelation, organometallics.