A 2023 paper in JACS suggested that the definition of hydrogen bonding should be extended to include hydrides. A team from Amsterdam recently responded in the same journal to argue for keeping the hydrogen bond definition as it is.

The International Union of Pure and Applied Chemistry (IUPAC) regulates the naming and definitions of chemical terms. It is vital that these definitions are clear; a wrong definition can lead to wrong theory and ultimately wrong applications.

Take the hydrogen bond (H-bond). IUPAC defines it as ‘an attractive interaction between a hydrogen atom from a molecule or a molecular fragment Y–H, in which Y is more electronegative than H, and an atom or group of atoms (Z), in which there is evidence of bond formation (i.e., a Y–H···Z hydrogen-bonded complex)’. This bonding motif is very well defined and understood: the bonding mechanism is a HOMO–LUMO interaction between the lone pair of Z and the σ* acceptor orbital of Y–H. This mechanism forms the basis of much theoretical and practical knowledge.