Diaquabis­[3-(hydroxy­imino)­butanoato]nickel(II)

In the neutral, mononuclear title complex, [Ni(C(4)H(6)NO(3))(2)(H(2)O)(2)], the Ni atom lies on a crystallographic inversion centre within a distorted octa­hedral N(2)O(4) environment. Two trans-disposed anions of 3-hydroxy­imino­butanoic acid occupy four equatorial sites, coordinated by the deprotonated carboxyl­ate and protonated oxime groups and forming six-membered chelate rings, while the two axial positions are occupied by the water O atoms. The O atom of the oxime group forms an intra­molecular hydrogen bond with the coordinated carboxyl­ate O atom. The complex mol­ecules are linked into chains along b by hydrogen bonds between the water O atom and the carboxyl­ate O of a neighbouring mol­ecule. The chains are linked by further hydrogen bonds into a layer structure.