Poly[μ-aqua-diaquabis[μ-2-cyano-2-(oxidoimino)acetato]copper(II)dipotassium]

In the title compound, [CuK2(C3N2O3)2(H2O)3]n, the Cu2+ atom is in a distorted square-pyramidal coordination geometry. Two N atoms belonging to the oxime groups and two O atoms belonging to the carboxylate groups of two trans-disposed doubly deprotonated residues of 2-cyano-2-(hydroxyimino)acetic acid make up the basal plane and the apical position is occupied by the water molecule. The neighboring Cu-containing moieties are linked into a three-dimensional framework by K—O and K—N contacts formed by two potassium cations with the carboxylate and the oxime O atoms and the nitrile N atoms of the ligand. The environments of the K+ cations are complemented to octa- and nonacoordinated, by K—O contacts with H2O molecules. The crystal structure features O—H⋯O hydrogen bonds.

In the title compound, [CuK 2 (C 3 N 2 O 3 ) 2 (H 2 O) 3 ] n , the Cu 2+ atom is in a distorted square-pyramidal coordination geometry. Two N atoms belonging to the oxime groups and two O atoms belonging to the carboxylate groups of two transdisposed doubly deprotonated residues of 2-cyano-2-(hydroxyimino)acetic acid make up the basal plane and the apical position is occupied by the water molecule. The neighboring Cu-containing moieties are linked into a threedimensional framework by K-O and K-N contacts formed by two potassium cations with the carboxylate and the oxime O atoms and the nitrile N atoms of the ligand. The environments of the K + cations are complemented to octaand nonacoordinated, by K-O contacts with H 2 O molecules. The crystal structure features O-HÁ Á ÁO hydrogen bonds.
The title compound, [K 2 Cu(C 3 N 2 O 3 ) 2 (H 2 O) 3 ] n , has an ionic structure containing 2-charged Cu(II)-centered complex anions, potassium cations and water molecules (Fig. 1). The Cu atom is in a distorted square-pyramidal geometry, defined by two N atoms belonging to the oxime groups and two O atoms belonging to the carboxylic groups of two transdisposed doubly deprotonated residues of 2-cyano-2-(hydroxyimino)acetic acid. The apical position is occupied by the water molecule O1W which also serves as a bridge between Cu1 and K1 ions. The coordination bond lengths Cu-N and Cu-O (Table 1) are typical for square-pyramidal Cu(II) complexes with deprotonated oxime and carboxylate donors Kanderal et al., 2005). The bite angles around the central atom deviate from an ideal square-planar configuration [e.g. O2-Cu1-N1 = 82.89 (6)°], which is a consequence of the formation of five-membered chelate rings. The bond lengths C-O, N-O and C-N in the coordinated 2-oximinocarboxylate ligand are typical for copper(II) complexes with cyanoximes and carboxylates (Onindo et al., 1995;Duda et al., 1997;Fritsky et al., 2004;).
The potassium cations K1 and K2 are bound to the copper(II) complex anion in a chelate fashion via the oxime oxygen (O1A and O1, respectively) and the carboxylic oxygen (O2 and O2A, respectively) atoms. Such coordination of two potassium cations from the different side of the complex anion results in a closed metallamacrocylic framework. Both potassium cations also forms additional K-O and K-N contacts with the carboxylic and the oxime O atoms and the nitrile N atoms of the neighboring Cu complex anions thus uniting them in a three-dimensional framework (Fig. 2). The environments of K1 and K2 potassium cation are complemented to octa-and nona-coordinated, respectively, by K-O contacts with H 2 O molecules. The K-O and K-N bond lengths are normal for potassium cations and close to those reported in the structures of the carboxylate and the oximate complexes (Fritsky et al., 1998;Świątek-Kozłowska et al., Kovbasyuk et al., 20040). The crystal structure involves intermolecular O-H···O hydrogen bonds where the water molecules act as donors, and the carboxylic and the oxime O atoms act as acceptors (Table 2).

Refinement
The H atoms of the water molecule were located at the difference Fourier map and their coordinates were allowed to ride on the coordinates of the parent atom with U iso (H) = 1.5U eq .

Poly[µ-aqua-diaquabis[µ-2-cyano-2-(oxidoimino)acetato]copper(II)dipotassium]
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.