Diaquabis(2-hydroxyiminopropionato-κ2N,O)copper(II)

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 CuII 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) A, 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 Cambridge Crystallographic Data Centre, Cambridge, England] but remained unpublished.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—H⋯O hydrogen bonds between methyl groups and the hydroxyl O atoms of hipa. The shortest Cu⋯Cu 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.