Hydrogen–deuterium exchange at a saturated carbon atom in tertiary phosphine complexes of platinum(II)

Abstract

Chloro-bridged diplatinum(II) complexes of the type [Pt₂Cl₄L₂](L = PPr₃, PBu₃, PBu^tPr₂, PBu^t₂Pr, PPrPh₂, PPr₂Ph, or PBu^tPh₂), undergo a regiospecific hydrogen-deuterium exchange in an aqueous (D₂O) acetic acid (CH₃CO₂D) medium to give complexes containing deuterium in the alkyl groups of the tertiary phosphine moiety and, in the case of L = PBu^tPh₂, also in the aryl groups. The steric requirements of the tertiary phosphine have a marked influence on both the rate and the position of deuterium incorporation. The results presented show that, in internal-metallation reactions of platinum, the ease of ring formation decreases in the order five-membered > six-membered > four-membered rings. It is suggested that in such reactions steric rather than electronic factors are dominant.