2-Pyridylcyanoxime-NiII Clusters with Unusual Topologies: Lone-Pair-π Interactions and Magnetic Properties

Three new complexes derived from the reaction of the 2-pyridylcyanoxime ligand (pyC{CN} NOH) with several non-carboxylate nickel salts have been structural and magnetically characterized. The compounds with the formula [Ni-3(MeOH)(2)-(CF3COO)(OH)(pyC{CN}NO)(4)] (1), [NaNi(tfacac)(3)](n) (2; tfacac = 1,1,1-trifluoroacetylacetone), [Ni-5(H2O)(2)(N-3)(2)(pyC{CN}NO)(8)] (3), and [Ni-3(pyC{CN}NO)(5)(pyC{CN}NOH)](BF4) (4) exhibit unusual topologies with a triangular {Ni-3(mu(3)-OH)-(pyC{R'}NO)(3)}(2+) core for 1, vertex-shared triangles with a {Ni-5(mu(1,1)-N-3)(2)(pyC{CN}NO)(6)}(2+) core for 3, and a {Ni-3(pyC-CN}NO)(4)}(2+) core for 4. Direct-current (DC) magnetic measurements performed in the 2-300 K temperature range reveal antiferromagnetic interactions induced by the mu(3)-OR or oximato superexchange pathways and ferromagnetic interactions promoted by the azido bridges, thereby resulting in ground states S = 0, 3, and 1 for 1, 3, and 4, respectively. Supramolecular lone-pair-pi-ring interactions are reported for the first time for the pyC{CN}NO- ligand and its importance in the crystal packing is discussed.