Acta Cryst. (2007). E63, m1670-m1671  [ doi:10.1107/S160053680702226X ]

Diaquabis(2-hydroxyiminopropionato-²N,O)copper(II)

M. V. Kirillova, M. Haukka, A. M. Kirillov, J. A. L. Silva, J. J. R. Fraústo da Silva and A. J. L. Pombeiro

Abstract: The 100 K crystal structure of the title compound, [Cu(C₃H₄NO₃)₂(H₂O)₂], is composed of discrete [Cu(hipa)₂(H₂O)₂] units (hipa = 2-hydroxyiminopropionate). The Cu^II atom lies on an inversion centre and exhibits a slightly distorted octahedral coordination geometry formed by two chelating bidentate hipa ligands occupying equatorial sites and two water molecules in axial positions. The hipa ligands are bound to the copper centre in a trans fashion, generating a planar {Cu(hipa)₂} core with the six-membered chelate rings having Cu-O and Cu-N distances of 1.9421 (13) and 2.0488 (15) Å, respectively, and N-Cu-O bite angles of 80.70 (6)°. The bonding parameters agree with those of the 298 K crystal structure of the title compound, which has been deposited at the Cambridge Structural Database (refcode IGUZAL) [Holt (2002). Private communication to the Cambridge Structural Database. Cambridge Crystallographic Data Centre, Cambridge, England] but remained unpublished. In the title compound, each water molecule acts as both an intermolecular hydrogen-bond donor (to the carboxylate O atoms) or acceptor (of hydrogen from the hydroxyl oxygen), thus multiply linking neighbouring mononuclear units and forming polymeric hydrogen-bonded two-dimensional layers. They are further extended by means of weak intermolecular C-HO hydrogen bonds between methyl groups and the hydroxyl O atoms of hipa. The shortest CuCu separations within these layers are equal to the unit-cell dimensions. The hipa ligands in the title compound are derived from a copper-promoted fragmentation of N-hydroxy-2,2'-iminodipropionic acid.

Online 23 May 2007

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