A number of processes involve metal catalysts where the metal carries
sulfur-donor ligands. Three are discussed where metal complexes with S
-donor ligands are being used to elucidate potential reaction pathways
. This primarily involves the reductase nitrogenase and the metals van
adium, molybdenum, and iron but aspects of molybdenum chemistry involv
ed in the function of the hydroxylase xanthine oxidase and of hydrodes
ulfurization of feedstock gases are also considered.