Less Known Redox-active Ligands in Metal Complexes

5 LESS KNOWN REDOX-ACTIVE LIGANDS IN METAL COMPLEXES 

As briefly alluded to, there are different classes of redox-active ligands in addition to the above mentioned ones. For example, we have seen in Chapter 5, Section 8, that azo-groups (in particular, 2-(phenylazo)pyr-imidine) are able to undergo two separate one-electron reduction processes. Conjugated polynitriles (mnt, tcne, tcnq) also constitute an important class of redox-active molecules and the electrochemical behaviour of their metal complexes has been reviewed.107 The same holds as far as alkyldithiocarbamates (Rdtc) and their metal complexes are concerned,108 or nitrosyl complexes in their possible NO+[NO fNO redox sequence.109 Thus, we would like to conclude the present Chapter by discussing a few less known redox non-innocent ligands. 

As shown, the distorted octahedral Zn(II) complex undergoes two separated (one-electron) reductions, reversible in character, 

As a matter of fact, the crystal structures of the couple [Con(L)2]2+/ [Co L) + have been solved and the relevant parameters are compiled in Table 14.110b 

As seen, the only significant structural variations are concerned with the metal-ligand bonds, thus supporting that, in this case, the first reduction is metal-centred. 

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