2-pyridylcyanoxime-NiII clusters with unusual topologies: lone pair-p interactions and magnetic properties

Abstract

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.Thecompounds with the formula [Ni3(MeOH)2- (CF3COO)(OH)(pyC{CN}NO)4] (1), [NaNi(tfacac)3]n (2; tfacac = 1,1,1-trifluoroacetylacetone), [Ni5(H2O)2(N3)2(pyC{CN}NO)8] (3), and [Ni3(pyC{CN}NO)5(pyC{CN}NOH)](BF4) (4) exhibit unusual topologies with a triangular {Ni3(μ3-OH)-(pyC{R'}NO)3}2+ core for 1, vertex-shared triangles with a {Ni5(μ1,1-N3)2(pyC{CN}NO)6}2+ core for 3, and a {Ni3(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 μ3-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-π-ring interactions are reported for the first time for the pyC{CN}NO- ligand and its importance in the crystal packing is discussed