Hydrogen bonding in organometallic crystals .4. M-H center dot center dot center dot O hydrogen-boding interactions

M-H...O hydrogen-bonding interactions in crystalline organometallic complexes and clusters of the transition metals have been investigated. Molecular and crystal structures determined by neutron and/of X-ray diffraction data have been retrieved from the Cambridge Structural Database. In a number of cases there is clear manifestation of M-H...O hydrogen bonding involving metal-bound H(''hydride''), atom(s) and oxygen atoms mainly belonging to CO groups. When the H-ligands are electronically suited to being hydrogen-bonding donors, the absence of M-H...O interactions is due to the steric congestion around the coordination sites of the H-ligands. Individual crystal structures have been examined in detail. It is suggested that the M-H...O hydrogen bond is an example of a soft intermolecular interaction and is comparable in strength to C-H...O hydrogen bonds.