Dithiolene complexes electrochemistry

There is a large number of heteroleptic dithiolene complexes—complexes that contain at least one dithiolene and at least one other ligand. This chapter is focused on mononuclear and relatively simple dinuclear complexes. The electrochemistry of heteroleptic dithiolene complexes is only briefly discussed in view of the limited amount of data available. Oxodithiolene complexes are often studied as structural models for Mo and W enzymes and are reviewed in Chapter 10 in this volume (113). Focused here is the chemical reactivity of selected types of heteroleptic dithiolene complexes. 

Bowden et al.152 studied the electrochemistry of the Ni, Pd and Pt ptt complexes and of their SacSac derivatives and compared it with that of the dithiolenes, pointing out the dangers of the even-odd distinction. Both the dithiolenes and the ptt complexes undergo two ligand-based one-electron reductions. However, the reduction of the ptt complexes requires much more (approximately 1V) negative potentials the reductions are close to irreversible. This means that the anionic species derived from ptt and SacSac complexes are much less stable than the dithiolene mono- and di-anions, in accord with the MO results of Figure 2. 

The rednctive electrochemistry of several Ni complexes of unsaturated dithiolate ligands has been examined. On the basis of the electrochemical redox potentials, EPR spectral evidence, and SCF calculations, these rednction products are best formulated as Ni complexes for dithiocarbamate and 1,2-dithiolene hgands, and as Ni stabihzed ligand-radical anions for dithiodiketonate species. It is often difficnlt to assign electron-density distributions within a molecnle, particnlarly with delocahzed hgands such as dithiolenes. 

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