Binary salt of a palladium(II) complex with (phosphonomethyl)phosphonic (medronic) acid comprising `handbell-like' [Pd{[mu]-CH2(PO3)2}]3 units

The asymmetric unit of the title compound, dipotassium bis[hexaaquanickel(II)] tris([mu]2-methylenediphosphonato)tripalladium(II) hexahydrate, K2[Ni(H2O)6]2[Pd3{CH2(PO3)2}3]·6H2O, consists of half a {[Pd{CH2(PO3)2}]3}6- anion [one Pd atom (4e) and a methylene C atom (4e) occupy positions on a twofold axis] in a rare `handbell-like' arrangement, with K+ and [Ni(H2O)6]2+ cations to form the neutral complex, completed by three solvent water molecules. The {[Pd{CH2(PO3)2}]3}6- units exhibit close Pd...Pd separations of 3.0469(4)Å and are packed via intermolecular C--H...Pd hydrogen bonds. The [KO9] and [NiO6] units are assembled into sheets coplanar with (011) and stacked along the [100] direction. Within these sheets there are [K4Ni4O8] and [K2Ni2O4] loops. Successive alternation of the sheets and [Pd{CH2(PO3)2}]3 units parallel to [001] produces the three-dimensional packing, which is also supported by a dense network of hydrogen bonds involving the solvent water molecules. [PUBLICATION ABSTRACT]