Chlorine Binds Gold Covalently

Although all halogens are thought to bind to metal surfaces through ionic interactions, new theoretical evidence indicates that chlorine breaks this rule when interacting with a gold surface (J. Am. Chem. Soc., DOI: 10.1021/ja7109234). In this exceptional case, bonding between chlorine and the gold surface is primarily covalent in character, report Thomas A. Baker, Cynthia M. Friend, and Efthimios Kaxiras of Harvard University. The researchers used density functional theory to study chlorine on gold, a system of particular interest because of the role it plays in gold catalysis. For example, chlorinating reagents have been used in combination with solid-supported gold catalysts to remove environmental mercury, and chlorine can be used to increase the selectivity of styrene oxidation on unsupported gold surfaces. The Harvard team suggests that gold's unusually high electronegativity makes it the transition metal most likely to form a covalent bond with highly electronegative halogens such as chlorine.