A series of well-defined thiolate-bridged diiron clusters bearing the cis-HN = NH ligand, [Cp+Fe(mu-SEt)(2)-(mu-eta(1):eta(1)-HN = NH)FeCp+][PF6] (Cp+ = eta(5)-C5Me4H or eta(5)-C5Me5), are successfully prepared in high yields and fully characterized by spectroscopy and X-ray crystallography. Under moderate conditions, these new Fe/S clusters exhibit high activity, not only for the catalytic cleavage of the N-N bond of hydrazines but also for the activation and coupling of terminal alkynes.