Reactions of Iridium iv

Studies of oxidation reactions of differing substrate types have been described. The nature of oxidant species in HCIO4 and H2SO4 media has been examined by investigation of catalysis of the Ce -Hg reaction. It is suggested that at 2.OM-HCIO4 the iridium(iv) is hydrolysed with protonation constant of 0.4 for [Ir(H20)s0H] +. Most kinetic studies, however, refer to reaction of the hexachloro and hexabromo ions. The oxidation of thiourea (tu), iV,iV -dimethyl-thiourea (dmtu), and 2-imidazolidinethione (it) follows a rate law second order in [substrate] and first in [Ir ]. The rate of oxidation follows the reactivity trend established previously for aquo-metal ions. The mechanism proposed involves rapid pre-equilibria followed by disulphide radical formation, 

Several pathways have been identified in the oxidation of 2-mercaptosuccinic acid (H3L) in perchlorate media (pH 2—4). In conditions of excess of either oxidant or organic substrate, a sulphur-bonded copper(ii) transient absorbing at 350 nm (s= 1.6x 10 cm ) was detected within the time of mixing. The 

The formation of a dimer provides a two-electron template on which direct oxidation to the mercaptide can occur. After redox the copper(i) complex is stabilized by further co-ordination of thiol. 

The influence of anions on the rate of reduction of copper(ii) in the Cu -piperidine-benzene-A (A = N03-, C1-, Br-, or CIO4-) systems has been investigated. No redox is shown where A- = C1-, but for the other counter-ions Cu formation takes place. The results are interpreted in terms of the relative influence of c-donor and rr-acceptor ligands present in the Cu co-ordination sphere. 

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