Acid-induced reversal of amine attack at platinum-co-ordinated ethene versus acidolysis of platinum–carbon σ bonds

Abstract

The acidolysis of polynuclear platinum complexes of formula [{PtCl(tmen)(CH₂CH₂^–)}_nNEt_{4 –n}]⁺(tmen =NNN′N′-tetramethylethylenediamine, n= 1–4) to give polyalkylated ammonium ions has been carried out under different experimental conditions : (i) dilute perchloric acid in methanol; (ii) bubbling of gaseous hydrochloric acid through a chloroform solution of the complex; (iii) action of concentrated hydrochloric acid (37% in water) on the solid; and (iv) action of gaseous HCl on the solids. Overall it appears that on increasing the stability, and hence the resistance to undergo C–N bond dissociation, of the addition products, the alternative degradative path, that is cleavage of the Pt–C bond, becomes more important; the latter is also favoured by an increase in acid concentration and by a deshielding of the reaction centre. Moreover, heterogeneous conditions appear to favour Pt–C over C–N bond cleavage.