Binuclear Ni(II) complexes based on bridging oxalate and tetracyanometallates.: Synthesis, crystal structure and magnetic properties

The trimeric complexes, [{Ni(dien)}(2)(mu-ox){mu-Pd(CN)(4))}] (2) and [(Ni(dien)}(2)(mu-ox){(mu-PT(CN)(4))}] (3) were synthesised by the reaction of [{Ni(dien)(H2O)}(2)(mu-ox)](PF6)(2)(.)2H(2)O (dien = dietylenetriamine and ox = oxalate) with K2Pd(CN)(4) and K2Pt(CN)(4), respectively. In this reaction, water substitution and molecular reconstruction reactions take place to afford trimer complexes. These compounds are isostructural with the molecular compound [{Ni(dien)}(2)(mu-ox){(mu-Ni(CN)(4))}] (1). In each complex, the two octahedrally coordinated Ni atoms are oxalate bridged and the sphere of coordination of each Ni is completed by three nitrogen atoms from a diethylenetriamine ligand in fac arrangement and one nitrogen atorn from a bridging cyanide ligand, which belongs to the corresponding square-planar complex [M(CN)(4)](2-). The three compounds present antiferromagnetic behaviour. The magnetic coupling between the two nickel atoms might occur through both bridges, but the length of the exchange pathway through the bidentate tetracyanometallate ligands is large enough to predict that the magnetic interaction may take place mainly through the oxalate ligand. The values of this coupling are similar J (cm(-1)) = -31.2 (1), -33.5 (2) and -33.6 (3). (C) 2002 Elsevier Science Ltd. All rights reserved.