Quadruple bonds redox reactions

A number of excellent reviews have been written that address various aspects of metal-metal bonding. In particular, Cotton has contributed several eminent early reviews commensurate with his pioneering efforts in this area (54, 59, 60). More recently he reviewed quadruple bonds (56), molybdenum-molybdenum bonds (57), and multiple bond studies in his laboratory (55) in separate articles. Earlier reports discuss multiple metal-metal bonds in the context of general metal—metal bonding schemes and clusters at a time when the area was more limited in scope and therefore amenable to an encompassing survey (13, 128, 129, 164, 188, 189, 252). The redox behavior of metal-metal bonds has been reviewed by Meyer (193), and Walton has recently described ligand-induced redox reactions of strong multiple metal—metal bonds (253). 

The reactions discussed in this section include those in which monomeric reagents are converted into dimeric species containing quadruple bonds. Later sections of this review consider reactions in which substitution or redox processes occur with retention, alteration, or cleavage of the metal—metal multiple bond. In very general terms, it is the initial formation of the quadruple bond that is common to the reactions below, and the number and variety of... 

Quadruple bonded direhnium compounds possess a rich redox chemistry. As shown in the scheme in Fig. 1.39 the combination of chemical and electrochemical reactions leads to a variety of dimetal compounds. 

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