If the complex is an anion, the name ends in -ate. The oxidation state of the metal is given in Roman numerals in parentheses after the name of the metal. 24.3 Isomerism isomers Structural isomers Stereoisomers linkage isomerism coordination-sphere isomerism . The color of a complex depends on the metal, the ligands present, and the oxidation state of the metal. A partially filled d subshell is usually required for a complex to be colored.
Colored compounds absorb visible light.
An object will have a particular color if it reflects or transmits that color or if it absorbs light of the complementary color. An object appears black if it absorbs all wavelengths of light. An object appears white or colorless if it absorbs no visible light. The formation of a complex is a Lewis acid base interaction. Both electrons in the bond come from the ligand and are donated into an empty hybridized orbital on the metal.