Dinuclear diazene iron and ruthenium complexes as models for studying nitrogenase activity

The strength of hydrogen bonds has been investigated in various dinuclear d iazene Fe-II, Fe-III, and Ru-II complexes by use of the recently developed shared-electron number approach. Hydrogen bonding in these compounds plays an essential role in view of designing a model system for nitrogenase activ ity. The general conclusions for iron-sulfur complexes are: hydrogen bonds can stabilize diazene by at least 20 % of the total coordination energy; th e strength of the hydrogen bonds can be directly controlled through the hyd rogen-sulfur bond length; reducing Fe-III centers to Fell can double the hy drogen bond energy.