A mononuclear molybdenum(V) mono-oxo biphenyl-2,2 '-dithiolate complex in which the metal resides within a cleft formed by the ligands and that exhibits N-(HS)-S-center dot center dot center dot hydrogen bonding in the solidstate

The reaction of Mo(O)(2)(acac)(2), H2L (2,2'-dimercaptobiphenyl), and NEt3 produced the mononuclear Mo(V) complex Et3NH[Mo(O)(L)(2)] (1). Molybdenum m ono-ore tetrathiolate complexes such as 1 are studied as potential structur al or functional models for pyranopterin-containing molybdoenzymes. Complex 1 has been crystallographically characterized. The solid-state structure r eveals that the molybdenum ion sits within a cleft formed by the biphenyl b ackbone of the ligands, providing some steric protection. In addition, ther e is a hydrogen bond between the amine hydrogen of [Et3NH](+) and one of th e thiolate sulfur atoms. A difference in solution reactivity between 1 and a derivative without a hydrogen-bonding counterion suggests that hydrogen b onding occurs in solution also. There are two short S-S contacts End small S-Mo-S angles in the structure of 1 that may reflect a slight bonding inter action. Such short S-S distances and small angles have been found in a coup le of other Mo-thiolate complexes and in many of the molybdoenzyme crystal structures. Further characterization df 1 by EPR, IR, and UV-vis spectrosco pies, as well a's by cyclic voltammetry, is discussed and compared to known Mo(V)-oxo-tetrathiolate complexes as well as to relevant molybdoenzyme dat a. Reactions to generate Mo(VI) complexes from 1 resulted in net oxidation at the ligand to form its disulfide derivative, which dissociated from the metal center. This result suggests that modifications to the ligand to prev ent this process are needed.