Redox kinetics of Chini-type platinum carbonyl clusters studied by time-resolved pulse radiolysis

The reduction mechanism of Chini clusters [Pt-3(CO)(6)]n(2-) (n = 6-9) has been studied by nanosecond pulse radiolysis in water/2-propanol solution. The monoelectronic reduction of all [Pt-3(CO)(6)](6)(2-) by the alcohol radicals produced by the solvent radiolysis is supposed to yield short-lived [Pt-3(CO)(6)](6)(3-) clusters that split immediately into [Pt-3(CO)(6)](4)(2-) and [Pt-3(CO)(6)](2-) [Pt-3(CO)(6)](2)(-) dimerizes to the stable tetramer [Pt-3(CO)(6)](4)(2-) with a diffusion-controlled rate constant. When only a fraction of the [Pt-3(CO)(6)](6)(2-) in solution is reduced, a slower addition reaction between excess [Pt-3(CO)(6)](6)(2-) and the newly formed [Pt-3(CO)(6)](4)(2-) gives then two [Pt-3(CO)(6)](6)(2-). Results concerning the early steps of the reduction of clusters of higher nuclrarity [Pt-3(CO)(6)](n)(2-) (n = 7-9) are also presented. The general reduction mechanism of the platinum carbonyl compounds [Pt-3(CO)(6)](n)(2-) displays some similarities with the reduction of n = 6; i.e., stable [Pt-3(CO)(6)](4)(2-) are formed together with the transient [Pt-3(CO)(6)](n-4)(-).