Reaction of anionic oxygen donors with the antitumour copper(II)–pyridine-2-carbaldehyde thiosemicarbazone (HL) system and the crystal structure of [{Cu(HL)(H2PO4)}2][H2 PO4]2·2H3PO4 ·2H2O

The complexes [(CuL) 2 (XO 4 )]·nH 2 O (HL = pyridine-2-carbaldehyde thiosemicarbazone, X = HP, n = 6; X = Mo, n = 1), [{CuL(ptp)} 2 ]·4H 2 O (Hptp = p-tritylphenol) and [{CuL(tip)} 2 ] (Htip = 2,4,6-triiodophenol) have been prepared from the reaction of aqueous solutions of [{CuL(CH 3 CO 2 )} 2 ] with salts of the appropriate oxygen donor. Also prepared were [{Cu(HL)(H 2 PO 4 )} 2 ][H 2 PO 4 ] 2 ·xH 3 PO 4 ·nH 2 O (x = 0, n = 3; x = 2, n = 2) from the reaction of [{CuL(CH 3 CO 2 )} 2 ] with 2 mol dm -3 H 3 PO 4 and phosphate species (arising from the hydrolysis of 2 mol dm -3 HPF 6 ) respectively. The complexes have been characterized by a range of physicochemical techniques and the crystal and molecular structure of [{Cu(HL)(H 2 PO 4 )} 2 ][H 2 PO 4 ] 2 ·2H 3 PO 4 ·2H 2 O determined by single-crystal X-ray diffraction. The complex cation is a centrosymmetric dimer, the monomeric units having one-atom bridges from two H 2 PO 4 - anions. The copper atom has a distorted square-pyramidal geometry with three donor atoms (NNS) from the neutral, tridentate HL ligand and the fourth in-plane donor (an oxygen) from the bridging anion. The fifth position is occupied by a less strongly bound oxygen from the second bridging anion. An extensive hydrogen-bonding scheme involving the bridging H 2 PO 4 - anions, non-co-ordinated H 2 PO 4 - anions, H 3 PO 4 moieties, water molecules and ligand exists with one very strong contact of 2.436 Å. These complexes may serve as simple models for the interaction of this antitumour system with oxygen donors.