Synthesis and cleavage reactions of metal-metal-bonded [Mo(2)(S(2)CNR(2))(6)](OTf)(2), a source of the Tris(dithiocarbamato)molybdenum(IV) fragment.

Halide abstraction from the chlorotris(dialkyldithiocarbamato)molybdenum(IV) complexes MoCl(S(2)CNR(2))(3) (R = Et, Me) with silver triflate produces the diamagnetic dimeric complexes Mo(2)(S(2)CNR(2))(6)(2) in good yield. The crystallographically determined structure of the diethyldithiocarbamato complex indicates that the dimer consists of two pentagonal bipyramids sharing an axial edge, with a Mo-Mo separation (2.8462(8) A) indicative of a metal-metal bond. A qualitative analysis of the bonding indicates that this bond is of order 2 and consists of one normal sigma bond and one relatively weak "skewed pi" interaction. The dimers Mo(2)(S(2)CNR(2))(6)(2) react with a variety of reagents to give monomeric seven-coordinate complexes, including the new cationic molybdenum(IV) complex Mo(PMe(2)Ph)(S(2)CNEt(2))(3), which has been structurally characterized. Kinetic studies of the reaction of Mo(2)(S(2)CNEt(2))(6)(2) with halides indicate the presence of competing dissociative and associative substitution pathways, although neutral donors may react by different mechanisms.