High-dimensional azido-bridged cadmium(ii) polymeric complexes with bis(bidentate) diazineligands

Abstract

Five new Cd(II)-azido polymeric complexes with bis(bidentate) diazine Schiff bases as auxiliary bridging ligands have been synthesized and crystallographically characterized. The differences in side constituents of the coligands lead to different diazine-bridged binuclear units and hence to three different types of polymeric networks, all being 3-connected nets. In complex 1, [Cd₂(L¹)₂(N₃)₄]_n (L¹ = 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene), a single diazine ligand links two metal ions into a centrosymmetric binuclear unit, and each unit is connected with four neighbors via double azido bridges in the end-on (EO) mode, yielding 2-D layers with the (6,3) net topology. Complex 2, [Cd₂(L²)₂(N₃)₂]_n(ClO₄)_n·nH₂O (L² = 1,4-bis(2-pyridyl)-1-amino-4-methyl-2,3-diaza-1,3-butadiene), shows a layer structure with the (6,3) net topology, but the binuclear unit contains two diazine bridges and the neighboring units are interlinked via single azido bridges in the end-to-end (EE) mode. The remaining three complexes, [Cd₂(L)₂(N₃)₄]_n (L = 1,4-bis(2-pyridyl)-1-amino-2,3-diaza-1,3-butadiene for 3, 1-(2-pyridyl)-4-(2-pyrazinyl)-4-amino-1-methyl-2,3-diaza-1,3-butadiene for 4, and 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene for 5), are isostructural and form the 3-D (10,3)-b net with three different connectors around each node (the cadmium ion): adjacent cadmium ions are alternately bridged by double EO azido bridges and mixed EO azido-diazine double bridges to produce a chain, and each chain is connected to four neighboring chains by single EE azido bridges to generate the 3D framework.