New types of hydrogen bonds

Since 1990, several new types of hydrogen bonding have been identified involving transition metals or their complexes, for example, X–H⋯H–M, X–H⋯M and M–H⋯l.p. types. In addition, conventional X–H⋯l.p. hydrogen bonding has also been used in a number of contexts. Although the area is at an early stage of development, it already holds the promise of providing useful applications in inorganic chemistry and homogeneous catalysis.