Platinum redox with complexes

This method involves very simple and inexpensive equipment that could be set up m any laboratory [9, 10] The equipment consists of a 250-mL beaker (used as an external half-cell), two platinum foil electrodes, a glass tube with asbestos fiber sealed m the bottom (used as an internal half-cell), a microburet, a stirrer, and a portable potentiometer The asbestos fiber may be substituted with a membrane This method has been used to determine the fluoride ion concentration in many binary and complex fluondes and has been applied to unbuffered solutions from Willard-Winter distillation, to lon-exchange eluant, and to pyrohydrolysis distil lates obtained from oxygen-flask or tube combustions The solution concentrations range from 0 1 to 5 X 10 M This method is based on complexing by fluonde ions of one of the oxidation states of the redox couple, and the potential difference measured is that between the two half-cells Initially, each cell contains the same ratio of cerium(IV) and cerium(tll) ions... 

The kinetically-stabilized complexes of the cage ligands normally yield redox reagents free of the exchange problems often associated with simple complexes. Indeed, the redox chemistry of the complexes shows a number of unusual features for example, saturated cages of the type mentioned in Chapter 3 are able to stabilize rare (monomeric) octahedral Rh(n) species (d7 electronic configuration) (Harrowfield etal., 1983). In a further study, radiolytical or electrochemical reduction of the Pt(iv) complexes of particular cages has been demonstrated to yield transient complexes of platinum in the unusual 3+ oxidation state (Boucher et al., 1983). 

Dithiophosphato metal complexes are usually prepared by metathesis of metal halides with alkali metal or ammonium salts. A convenient method uses the redox reaction of his th iophosphory 1 )d is ulfanes (RO)2(S)PSSP(S)(OR)2, with metal species in low oxidation states resulting in the insertion of the metal into the sulfur-sulfur bond.24 Recently it was used for the synthesis of long alkyl chain, liquid platinum(II) dithiophosphates25 and for the synthesis of Ru (CO)2[S2P(OPr%]2 from Ru3(CO)i2 with (Pr 0)2(S)PSSP(S)(0Pr,)2.26... 

The occurrence of the redox-driven reversible assembling-disassembling process involving copper complexes of 16 has been verified through cyclic voltammetry experiments at a platinum electrode in a MeCN solution. Figure 2.17 shows the CV profile obtained with a solution of the double-strand helicate complex [ Cu 21 (16)212 +. 

The voltammetric results also suggest that while platinum is the cathode of choice for the I /I3 redox mediator, it should not be the optimal choice for cobalt complex-based mediators. Likewise, while carbon is a poor cathode with the I /I3 redox mediator system, it should be acceptable for any of the cobalt systems considered here. It must be noted that among the series of Fig. 17.20, one of the most promising cobalt complexes (Co(DTB)32 +) is nearly electrochemically inactive on FTO and ITO electrodes, meaning that the unwanted Co(III) to Co(II) reduction at the... 

Table 4 Redox Potentials for Platinum(II) Complexes with Aromatic Nitrogen Ligands...

In chloroform solvent, the platinum dithiolene complexes Pt(S2C2R2)2 are photooxidized between 300 and 350 nm, providing the complexes used are those for which the R groups result in redox potentials in the 0.1 to 0.5 V (vs SCE) range. The results are consistent with the reaction shown in equation (534).1849 Further work on this system identifies the fact that several excited states are probably photoreactive in this process,1850 and no definitive answer on the excited state reactivities is yet available. Very recently, however, highly structured solid-state emissions have been observed for Pt S2C2(CN)2 P(OR)3 2, and this data may help resolve some of these questions.1851... 

In many other cases, detailed examination of platinum(IV) substitution reactions has shown that the mechanisms involve oxidation-reduction steps. These redox reactions can be collected into two classes according to whether a bielectronic or a monoelectronic redox species reacts with the platinum complex (i.e. complementary and non-complementary redox reactions, respectively). 

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