High pressure cyanide exchange study on a square-planar tetracyanometalate complex of Pt(II)

Abstract

Previous studies of cyanide exchange on square planar tetracyanoplatinate complex [Pt(CN)₄]^2- have been undertaken only at a high pH. For a more complete fundamental understanding of this system we extended the investigations of these exchanges over a large pH range. NMR kinetics methods (magnetisation transfer, isotopic exchange) proved to be very useful for obtaining quantitative rate data of the cyanide exchange on this complex. In fact it is quite significant that the reactivity of this metal center spans a ca. 9-order of magnitude range as a function of pH.

Variable temperature and variable pressure studies were undertaken in aqueous solutions and the following activation parameters obtained: ΔH‡ = (25.1 ± 0.4) kJmol⁻¹ and activation entropy ΔS‡ = -(142±2)JK⁻¹mol⁻¹ and activation volume ΔV‡ = -(27±2)cm³mol⁻¹.

Key Words:

• Platinum
• cyanide exchange kinetics
• high pressure NMR
• activation volume