Pyrazine-dioxide complexes of copper(II) tetrafluoroborate and perchlorate

Reaction of copper tetrafluoroborate or perchlorate hexahydrate with pyrazine-1,4-dioxide (pzdo) in water or water/methanol generated three compounds: [Cu2(pzdo)3(H2O)2(BF4)4]H2O (1), [Cu2(pzdo)3(H2O)2(ClO4)4]H2O (2), and [Cu(pzdo)3](BF4)2 (3). Compounds 1 and 2 are isostructural and crystallize in a two-dimensional brick-wall pattern with three bridging pzdo and the geganions semi-coordinate in the axial Cu-sites. Compound 3 also exhibits bridging pzdo ligands which link the Cu(II) ions into a three-dimensional lattice with the geganions in the lattice voids. Variable temperature magnetic susceptibility data on 1 and 2 indicates the presence of antiferromagnetic interactions which were fitted using the strong-rail ladder model to give: CC = 0.426(2) emu-K/mol-Oe, Jkrail = −104.9(4) K, and Jkrung = −80.9(2) K (1) and CC = 0.398(6) cm3-K/mol, Jkrail = −98(2) K, and Jkrung = −33.2(2) K (2). Although insufficient pure material was obtained for quantitative determination of the magnetic properties of 3, it is clear that the dominant interactions are antiferromagnetic.