Koordinaatiosidos

Koordinaatiosidos, often called a coordinate covalent bond, is a type of covalent bond in which both electrons of the bond originate from the same atom. This occurs when a Lewis base (a donor with a lone pair) donates an electron pair to a Lewis acid (an acceptor with an empty orbital). After formation, the bond is typically treated, in terms of bonding and electron counting, as a normal covalent bond, but the electron pair is supplied by the donor.

The concept is central to coordination chemistry and organometallic chemistry. In practice, many ligands such as ammonia, water, carbon monoxide, or cyanide donate lone pairs to metal centers, forming coordination bonds that hold ligands in place around the metal. Examples include the ammonia complex [Cu(NH3)4]2+ or hexacyanometalate ions [Fe(CN)6]n−, where the donor atoms (N, O, C, etc.) provide electron pairs to the central metal atom or ion. In a structural formula, a coordinate bond can be drawn as a regular single bond or indicated with an arrow from the donor to the acceptor, though in many modern treatments it is counted as a standard covalent linkage for purposes of electron counting and bonding descriptions.

Coordination bonds are characterized by donor-acceptor interactions, and their strength depends on the donor’s ability, the acceptor’s accepting orbitals, and the overall ligand field. The concept is widely used to describe stability, geometry, and reactivity of coordination complexes, catalysts, and many inorganic compounds.