Synthesis, crystal structure and magnetic properties of the three-dimensional compound [Na2Ni(mal)(2)(H2O)(6)](n) (H(2)mal = malonic acid)

A new three-dimensional nickel-sodium compound of formula [Na2Ni(mal)(2)(H2 O)(6)](n) (H(2)mal = malonic acid) was prepared and its structure was deter mined by X-ray diffraction methods. Four malonate-oxygen atoms and two tran s-(Ni) or cis-(Na) coordinated water molecules build distorted octahedral s urroundings around the metal atoms. The malonate group exhibits bidentate ( Ni) and tetrakis-monodentate (Na) coordination modes. The structure can be described as corrugated sheets of laalonato-containing Ni(II) and Na(I) cat ions which grow in the (101) plane, each sheet being linked to the adjacent one in the [101] direction through bis(mu-aqua)disodium(I) units. Within e ach corrugated sheet, the nickel atoms define a square lattice, the edge an d the diagonal being 8.895(3) and 12.579(3) Angstrom, respectively. Variabl e-temperature magnetic susceptibility measurements (2.0-290 K) reveal the o ccurrence of a very weak antiferromagnetic interaction between the nickel(I I) ions. (C) 2000 Elsevier Science S.A. All rights reserved.