Tripotassium (bis{[bis(carboxylatomethyl)amino]methyl}phosphinato)cuprate(II) dihydrate

In the title compound, K3[Cu(C10H12N2O10P)]·2H2O, the CuII ion, one potassium cation and a P atom are situated on a twofold rotation axis. The CuII ion is coordinated by two N and four O atoms from one bis{[bis(carboxylatomethyl)amino]methyl}phosphinate ligand in a distorted octahedral coordination geometry. The two crystallographically independent potassium ions exhibit different coordination environments. The potassium ion in a general position is heptacoordinated by five carboxylate O atoms, one phosphinate O atom and one water molecule [K—O = 2.718 (3)–3.040 (3) Å], and the potassium ion situated on the twofold rotation axis is hexacoordinated by four carboxylate O atoms and two water molecules [K—O = 2.618 (3)–2.771 (3) Å]. The water molecules are also involved in formation of intermolecular O—H⋯O hydrogen bonds.

In the title compound, K 3 [Cu(C 10 H 12 N 2 O 10 P)]Á2H 2 O, the Cu II ion, one potassium cation and a P atom are situated on a twofold rotation axis. The Cu II ion is coordinated by two N and four O atoms from one bis{[bis(carboxylatomethyl)amino]methyl}phosphinate ligand in a distorted octahedral coordination geometry. The two crystallographically independent potassium ions exhibit different coordination environments. The potassium ion in a general position is

Experimental
Crystal data K 3 [Cu(C 10 H 12 N 2 O 10 P)]Á2H 2 O M r = 568.06 Orthorhombic, P2 1 2 1 2 a = 11.880 (7) Å b = 8.332 (5) Å c = 9.681 (6)   a good example which could be structurally looked as two equal half of edta connected by a phosphinate group. Previous research (Xu et al., 2001) has demonstrated that XT 5is able to form stable complexes with rare earth metal and cobalt ions.
Herewith we present the crystal structure of the title compound (I).
In (I) (Fig. 1), the Cu II ion exhibits a distorted octahedral coordination geometry, where two N and two carboxylate O atoms located at the equatorial positions. Other two carboxylate O atoms occupy the axial positions. The Cu II ion, one potassium cation and a P atom are situated on a twofold axis. Two types of potassium ions with different coodination circumstances are distributed in the title complex (Fig. 2). K1 is hexacoordinated by four carboxylate O atoms and two water molecules; while K2 is heptacoordinated by five carboxylate O atoms, one phosphinate O atom and one water molecule.
The bond distances and angles in the title coupound agree well with the corresponding bond distances and angles reported in related [Co(II)XT] 3complex (Xu et al., 2001).
The title complex was simply synthesized by mixing 0.4027 g XT, 0.1774 g CuCl 2 and 5 ml water in a small beaker with sufficient stirring. When the solution became clear, KOH was used to adjust the pH value to 8. Then the beaker was transferred to a closed container of methanol. After methanol vapor diffusion for one week, blue transparent crystals were observed from the solution.