¹⁵N N.M.R. Study of Some Palladium(II) Ammine Complexes

Abstract

Palladium(II) ammine complexes enriched in ¹⁵N give sharp singlets in their ¹⁵N n.m.r . spectra. The ¹⁵N chemical shifts depend primarily on the trans donor atom, in a qualitatively similar way to those for platinum(II) ammine complexes. A dimethylformamide solution of Pd(NH₃)₂Cl₂ prepared in the usual way gave a single peak, consistent with the presence of only one isomer (trans). Reactions of increasing amounts of aqueous perchloric acid with Pd(NH₃)₄²⁺ allowed peaks to be identified for Pd(NH₃)₃(H₂O)²⁺, cis -Pd(NH₃)₂(H₂O)₂²⁺ and Pd(NH₃)(H₂O)₃²⁺. The initial product of the reaction of trans-Pd(NH₃)₂Cl₂ with silver ion is trans-Pd(NH₃)₂(H₂O)₂²⁺, which rapidly disproportionates to Pd(NH₃)₃(H₂O)²⁺ and Pd(NH₃)(H₂O)₃²⁺. With standing, subsequent reactions ultimately produce a solution containing predominantly cis -Pd(NH₃)₂(H₂O)₂²⁺ in equilibrium with small amounts of the tri- and mono-ammine complexes, and free ammonia.