NITROGEN ADSORPTION AND HYDROGENATION ON A MOFE6S9 COMPLEX

The enzyme nitrogenase catalyzes the biological nitrogen fixation where ${\mathrm{N}}_{2}$ is reduced to ${\mathrm{NH}}_{3}$. Density functional calculations are presented of the bonding and hydrogenation of ${\mathrm{N}}_{2}$ on a ${\mathrm{MoFe}}_{6}{\mathrm{S}}_{9}$ complex constructed to model aspects of the active site of nitrogenase. ${\mathrm{N}}_{2}$ is found to bind end on to one of the Fe atoms. A complete energy diagram for the addition of hydrogen to the ${\mathrm{MoFe}}_{6}{\mathrm{S}}_{9}$ complex with and without ${\mathrm{N}}_{2}$ is given, and a mechanism for ammonia synthesis is proposed on this basis.