The polymers containing ligand groups can bind metal ions forming polymer-metal complexes 1 . The metal-complexes, which have a free coordination site or a weak ligand, can also coordinate with the polymers. The ionic complexes can also form ionic compounds with the polymer acting as counter ion. The interaction of the piperazine ring and its derivatives with metal ions have been extensively studied in solid state 2-5 . In these compounds the piperazine group takes the chair conformation which

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... s the most stable. N,N'-disubstituted piperazines have found application as ligands in metal complexes and form the basis of various natural products that exhibit favourable pharmacological properties. Piperazine is conveniently substituted at the N and N' positions via reductive amination and nucleophilic substitution reactions 6 . Piperazine and substituted piperazine derivatives have been found to possess diverse biological activities like antimicrobial, antiplasmodial, anti-inflammatory, antioxidant and antipsychotic activity 7-9 . In this paper, the novel potassium piperazine complex is reported. All commercially obtained reagent-grade chemicals were used without further purification. A mixture of Ho2O3 (0.01 mmol, 0.004 g), dilute HNO3, KCl (0.1 mmol, 0.008 g), piperazine (0.1 mmol, 0.016 g) and boric acid (0.1 mmol, 0.009 g) were added into 20 mL water with 10 % (v/v) ethanol and heated for 5 h at 413 K. The solution was obtained by filtration after cooling the reaction to room temperature. Colourless block single crystals suitable for X-ray measurements were obtained after a few weeks.