Redox Kinetics of Chini-Type Platinum Carbonyl Clusters Studied by Time-Resolved Pulse Radiolysis

Abstract

The reduction mechanism of Chini clusters [Pt3(CO)6]n2- (n = 6−9) has been studied by nanosecond pulse radiolysis in water/2-propanol solution. The monoelectronic reduction of all [Pt3(CO)6]62- by the alcohol radicals produced by the solvent radiolysis is supposed to yield short-lived [Pt3(CO)6]63- clusters that split immediately into [Pt3(CO)6]42- and [Pt3(CO)6]2-. [Pt3(CO)6]2- dimerizes to the stable tetramer [Pt3(CO)6]42- with a diffusion-controlled rate constant. When only a fraction of the [Pt3(CO)6]62- in solution is reduced, a slower addition reaction between excess [Pt3(CO)6]62- and the newly formed [Pt3(CO)6]42- gives then two [Pt3(CO)6]52-. Results concerning the early steps of the reduction of clusters of higher nuclearity [Pt3(CO)6]n2- (n = 7−9) are also presented. The general reduction mechanism of the platinum carbonyl compounds [Pt3(CO)6]n2- displays some similarities with the reduction of n = 6; i.e., stable [Pt3(CO)6]42- are formed together with the transient [Pt3(CO)6]n-4-.