Interpenetration Phenomena via Anion Template Effects in Fe(II) and Co(II) Coordination Networks with a Bis-(1,2,4-triazole) Ligand.

Seven new coordination networks, [Fe(tbbt) 3 ](BF 4 ) 2 ( 1 ), [Co(tbbt) 3 ](BF 4 ) 2 ( 2 ), [Fe(tbbt) 3 ](ClO 4 ) 2 ( 3 ), [Co(tbbt) 3 ](ClO 4 ) 2 ( 4 ), [Fe(NCS) 2 (tbbt) 2 ] ( 5 ), [Co(NCS) 2 (tbbt) 2 ] ( 6 ), and [Fe(H 2 O) 2 (tbbt) 2 ]Br 2 ·2H 2 O ( 7 ), were synthesized with the linker 1,1'-( trans -2-butene-1,4-diyl)bis-1,2,4-triazole (tbbt) and structurally investigated. The structure of complexes 1 - 4 is composed of three interpenetrating, symmetry-related 3D networks. Each individual 3D network forms a primitive, nearly cubic lattice ( pcu ) with BF 4 - or ClO 4 - anions present in the interstitial spaces. The structure of compounds 5 and 6 is composed of two-dimensional sql layers, which are parallel to each other in the AB stacking type. These layers are interpenetrated by one-dimensional chains, both having the same formula unit, [M(NCS) 2 (tbbt) 2 ] (M = Fe, Co). The structure of compound 7 consists of parallel, two-dimensional sql layers in the ABCD stacking type. The interpenetration in 1 - 6 is not controlled by π-π-interactions between the triazole rings or C=C bonds, as could have been expected, but by (triazole)C-H⋯F 4 B, C-H⋯O 4 Cl, and C-H⋯SCN anion hydrogen bonds, which suggests a template effect of the respective non-coordinated or coordinated anion for the interpenetration. In 7 , the (triazole)C-H⋯Br anion interactions are supplemented by O-H⋯O and O-H⋯Br hydrogen bonds involving the aqua ligand and crystal water molecules. It is evident that the coordinated and non-coordinated anions play an essential role in the formation of the networks and guide the interpenetration. All iron(II) coordination networks are colorless, off-white to yellow-orange, and have the metal ions in the high-spin state down to 77 K. Compound 5 stays in the high spin state even at temperatures down to 10 K.