eighteen-electron rule

An electron-counting rule to which an overwhelming majority of @S05900@ @D01668@ transition metal complexes adhere. The number of nonbonded electrons at the metal plus the number of electrons in the metal-ligand bonds should be 18. The 18 electron rule in transition metal chemistry is a full analogue of the '@LT07065@'.
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1108 [Terms] [Paper]