noun
ligand
Chemistry term for an ion or molecule that binds to a central metal atom to form a coordination complex.
この錯体では、アンモニアが配位子として働いている。
In this complex, ammonia acts as a ligand.
配位結合 is the coordinate bond formed between the ligand and the central atom.
Compound of 配位 (coordination) and 子 (small thing, particle). The term is a modern scientific coinage for 'ligand'.