Distance and scalar HH-Coupling correlations in transition metal dihydrides and dihydrogen complexes

The bond-valence bond-length concept has been applied to derive a correlation between the hydrogen-hydrogen and the metal-hydrogen distances in the nonclassical dihydrogen complexes and classical transition metal dihydrides. The parameters of this correlation are similar to those for strong hydrogen-bonded systems. The predicted correlation is supported by 18 neutron structures of transition metal dihydrides or dihydrogen complexes and 2 neutron structures of transition metal trihydride complexes. It is also shown that the bond-valence bond-length concept can also be used to establish a correlation between the dihydrogen distance r(HH) in dihydrogen/dihydride complexes and the scalar coupling constants J(HH)/J(HD)/J(HT) in the different isotopomers of these complexes.