Structural features of 3d metal compounds with 1-hydroxyethylidenediphosphonic acid

Structural features of 3d metal complexes with anions of 1-hydroxyethylidenediphosphonic acid (HEDP, H4L), in which the M: HEDP ratios are equal to 1: 2, 1: 1, 3: 2, and 5: 2, are discussed. The Cu(II): HEDP = 1: 2 complexes are characterized by five types of structures: monomeric structures trans-[Cu(H4 − nL)2(H2O)2]2 − 2n, cis-[Cu(H4 − nL)2(H2O)2]2 − 2n, and [Cu(L)2]6−; the dimeric structure { [Cu(H2L)(H2O)]2(μ 2-H2L)2}4− ; and the polymeric chain structure {[Cu(μ 2-H2L)2]2−}∞. Six coordination modes exhibited by HEDP in the Cu(II) compounds are described.