Tetrahalogen

Tetrahalogen refers to a chemical species that contains four halogen atoms in a single molecule. In inorganic chemistry, compounds described as tetrahalogen or tetrahalides often have a central atom bonded to four halogen ligands, forming a MX4 formula where M is a metal or main‑group element and X is a halogen such as fluorine, chlorine, bromine, or iodine. The four halogen substituents commonly lead to a tetrahedral coordination geometry around the central atom, although deviations can occur depending on electronic structure.

Common examples of tetrahalides include carbon tetrachloride (CCl4) and silicon tetrachloride (SiCl4), which illustrate the MX4 motif with chlorine as the halogen. Other well-known tetrahalides are germanium tetrachloride (GeCl4), tin tetrachloride (SnCl4), and titanium tetrachloride (TiCl4). These compounds vary in reactivity, volatility, and stability, but many are reactive with water and moisture, undergoing hydrolysis to form oxides or oxyhalides and hydrogen halide species.

Preparation of tetrahalides typically involves halogenation or chlorination of the element or its hydride, or halide exchange reactions. Industrial routes may include passing chlorine over the metal or reacting the corresponding oxide with halogens under controlled conditions. Some tetrahalides serve as important intermediates or reagents; for example, TiCl4 is a key Lewis acid catalyst and a precursor to titanium dioxide, while SiCl4 is used in the production of silica.

Safety and handling are important considerations for tetrahalides. They are often highly reactive with water, corrosive, and potentially toxic or irritating. Appropriate handling includes storage under inert atmosphere or dry conditions, use of proper PPE, and awareness of hydrolysis hazards.