Structure and magnetism of anionic dicyanamidometallate extended networks of types (Ph4As)[MII(dca)3] and (Ph4As)2[M2II(dca)6(H2O)]•xCH3OH, where dca = N(CN)2- and MII = Co, Ni

Anionic metal tris-dicyanamide complexes of type (Ph4As)[M(dca)(3)], where M = Co(II) and Ni(II) have been synthesised and characterised by X-ray crystallography, powder diffraction and derailed magnetic measurements. The anions form extended sheets with (4,4) connectivity and octahedral geometry about individual d-block ions. The cations lie in between the sheets and display cation-cation interactions of the pi...pi and 'multiple phenyl embrace' types. The nickel(II) complex, (Ph4As)[Ni(dca)(3)], displays long-range magnetic order, with an ordering temperature of 20.1 K. (Ph4As)[Co(dca)(3)], in contrast, did not show long-range order, but did show unusual field dependence of the magnetic moments at temperatures below 20 K. The syntheses also yield a second, needle-shaped product, (Ph4As)(2)[M-2(dca)(6)(H2O)].H2O . xCH(3)OH, which could be separated. They are isostructural and contain ladder-like 1D polymers which are cross-linked by hydrogen bonding into sheets; these sheets are separated by layers of cations. The cation layers again show multiple phenyl embraces and other supramolecular interactions. Magnetic studies on these hydrate-methanolate species show that they do not display long range order but, rather, very weak coupling. (C) 2001 Elsevier Science Ltd. All rights reserved.