Effect of weak interactions on the H...H distance in stretched dihydrogen complexes.

Computational and experimental results presented in this paper demonstrate that the H-H distance in stretched dihydrogen complexes can be hypersensitive to a variety of weak intra- and intermolecular interactions, including those with bulky ligands and solvent molecules, hydrogen-bonding interactions, or ion-pairing. Particularly, the complex IrH(H...H)Cl(2)(P(i)Pr(3))(2) which contains a stretched dihydrogen ligand in the crystalline form, as shown by neutron diffraction, is a trihydride in solution. The difference is due to the intermolecular Ir-Cl...H-Ir hydrogen bonding in the solid.