Crystal Structure of Catene-Di(μ-1-Hydroxyethane-1,1-Diphosphonato)copper(II) Ammonium Salt Dihydrate (NH4)2[Cu(H2L)2] • 2H2O

The crystal structure of (NH(4))(2)[Cu(H(2)L)(2)] center dot 2H(2)O (H(4)L = 1-hydroxyethane-1,1-diphosphonic acid) was determined by X-ray diffraction analysis. The copper atoms in the chain polymeric structure [Cu(H(2)L)(2)](n)(2n-) are combined in pairs by the H(2)L ligands functioning as a tridentate chelate bridge. The Cu atom has a distorted tetragonal-bipyramidal coordination (4+2), with four equatorial oxygen atoms from two H(2)L ligands (Cu-O 1.944 and 1.992 angstrom) and two axial oxygen atoms from another two H(2)L ligands (Cu-O 2.445 angstrom). The anionic chains, ammonium cations, and disordered molecules of water of crystallization are joined by a branched system of hydrogen bonds O-H center dot center dot center dot O and N-H center dot center dot center dot O.