Aqueous chemistry of platinum and palladium complexes. Part 2. Synthesis and crystal structure of a palladium hydroxo complex [Pd(terpy)(OH)]ClO₄·H₂O (terpy = 2,2′:6′,2″-terpyridine)

The complex [Pd(terpy)(ONO2)]NO3(terpy = 2,2′:6′,2″-terpyridine) can be prepared from the reaction of Pd(NO3)2 with terpy in dilute nitric acid or from metathesis of [Pd(terpy)Cl]Cl using AgNO3. It dissolves in water with hydrolysis of the co-ordinated nitrato group to form [Pd(terpy)(OH2)]2+. Attempts to isolate this complex were unsuccessful. Addition of sodium perchlorate to a solution of [Pd(terpy)(ONO2)]NO3 at pH 10.5 afforded orange needles of [Pd(terpy)(OH)]ClO4·H2O. The Pd–OH bond distance is 1.966(3)Å, and the hydroxo group forms strong hydrogen bonds with the molecule of water of crystallisation.