2-(Arylazo)pyrimidines (aapm) are N,N′-chelating ligands and synthesise orange-red complexes of composition [Pd(aapm)Cl2],1, with Pd(MeCN)2Cl2 in MeCN. The complex hascis-PdCl2 configuration [v(Pd-Cl): 340, 360 cm−1]. The treatment of Tollen’s reagent (‘AgOH’) leads to chelatative hydroxylation in the pendant aryl ring, affording a green phenolato complex, Pd(aapmO)Cl,5 (aapmO is deprotonated 2-((8-hydroxo)arylazo)pyrimidine). The reaction is also carried out by controlled addition of dilute sodium hydroxide in air or by the addition of PhIO/m-chloroperbenzoic acid to a MeCN suspension of the complex. A single Pd-Cl stretch at 360 cm−1 supports the composition of phenolato complex. Unlike Pd(aapm)Cl2 the hydroxylated product, Pd(aapmO)Cl, has a structured intense absorption in the visible region near 670 nm. The Pd-Cl bond in Pd(aapmO)Cl is highly sensitive to nucleophilic substitution and slowly hydrolyses in aqueous medium.