What is a complex?

Coordination compounds (complexes), also known as complexes, double salts and complexes, contain complex molecules or ions formed by the combination of central atoms or ions with several ligand molecules or ions through coordination bonds, and are usually called "coordination units". All compounds containing coordination units are called coordination compounds. The branch of chemistry that studies complexes is called coordination chemistry.

Naming method of extended data complex:

The naming of (1) complex depends on the naming of its inner boundary (i.e. coordination ion).

Generally, the naming method of coordination ions at the inner boundary of complexes is as follows: from right to left, the number of ligands-ligand names [different ligand names are separated by a dot]-combination-center ion name-center ion valence.

The valence of the central ion is calculated from the external ion charge/ligand charge according to the zero charge of the complex, and is expressed by brackets and Roman numerals after the central ion.

(2) Complexes can be regarded as salts. If the inner boundary is cation, the outer boundary must be anion; If the inner boundary is anion, the outer boundary must be cation. It can be named according to the naming method of salt, and it can be named as an acid or a chemical substance from right to left.

References:

Baidu encyclopedia-coordination compounds