MCl6n

MCl6n describes a class of coordination compounds consisting of a central metal atom or ion M bound to six chloride ligands. The six chloride donors give an octahedral coordination environment around M in many cases. The overall charge n depends on the oxidation state of M and the formal charges of the ligands, so MCl6 can be a neutral molecule when M is in a +6 oxidation state, while other species exist as hexachloro metalloate anions [MCl6]n− that are isolated as salts with counterions.

In terms of structure and properties, the M–Cl bonds form an approximately octahedral framework. When MCl6 is neutral, such as tungsten hexachloride WCl6, the compound often exhibits volatility and air sensitivity, reflecting the high oxidation state and covalent character of the M–Cl bonds. Many hexachloro complexes in salt form appear as [MCl6]n− anions in which the metal center remains six-coordinate and typically adopts an octahedral geometry. The electronic configuration of M determines magnetic behavior and color, with d-electron count influencing spin state and ligand-field transitions.

Synthesis and occurrence vary by metal. Neutral hexachlorides like WCl6 exist for certain high-oxidation-state metals. Anionic hexachloro complexes are commonly generated or isolated via salt metathesis, using appropriate countercations to stabilize the [MCl6]n− unit in solution or the solid state.

Applications of MCl6n species include serving as precursors in inorganic synthesis and materials chemistry. Safety considerations include the reactive and potentially toxic nature of chlorides and metal chlorides, requiring standard precautions and appropriate facilities.