metallicand

Metallicand is a term occasionally used in chemistry to denote the metal-containing portion of a compound, particularly in organometallic and coordination chemistry. Broadly, it refers to the fragment of the molecule that centers on the metal atom and includes the ligands directly attached to it, i.e., the metal center and its immediate coordination sphere, while the rest of the molecule forms the non-metal framework.

Usage and status: The term is not part of a standardized nomenclature and is encountered mainly in older or specialized texts. In contemporary literature, authors more often refer to the metal center, metal core, or the coordination sphere rather than metallicand. The concept is useful for discussing how a complex can be partitioned into a metal-containing fragment and the surrounding molecular framework, especially when comparing reactivity or electronic structure across related species.

Examples: In a complex such as [Ni(CO)4], the metallicand can be regarded as the nickel center together with its four coordinating carbonyl ligands, forming the metal-centered fragment. In ferrocene, Fe(C5H5)2, the metallicand may be taken as the iron atom with its directly bound cyclopentadienyl ligands, representing the metal-centered fragment of the molecule. Nonetheless, the exact scope of metallicand can vary by author, which is why more common terms are often preferred.

See also: coordination chemistry, organometallic chemistry, metal center, metal core, coordination sphere.