Novel Sandwich Coordination Polymers Composed of Cobalt(II), 1,2,4,5-Benzenetetracarboxylato Ligands, and Homopiperazonium Cations

Two novel cobalt(II) coordination polymers, (H4hpz)[Co3(BTEC)2(H2O)12]·11H2O (1) and (H4hpz)[Co(BTEC)(H2O)3]·3H2O (2) (H4hpz = homopiperazonium; BTEC = 1,2,4,5-benzenetetracarboxylate), have been
synthesized under aqueous conditions at room temperature and structurally characterized by single-crystal X-ray
diffraction. Compound 1 crystallizes in the triclinic space group P1̄ with a = 9.823(4) Å, b = 11.587(4) Å, c =
20.385(7) Å, α = 95.10(2)°, β = 92.423(19)°, γ = 98.90(2)°, and Z = 2. Compound 2 also crystallizes in the triclinic
space group P1̄ with a = 9.7755(17) Å, b = 11.208(3) Å, c = 11.224(2) Å, α = 60.304(12)°, β = 73.687(12)°, γ =
84.311(14)°, and Z = 2. Both compounds have layered structures. In the case of 1, homopiperazonium cations and
1D anionic chains of [Co(BTEC)(H2O)4]2-n are sandwiched between 2D sheets of [Co2(BTEC)(H2O)8]n. In the case of
2, homopiperazonium cations alone are sandwiched between 2D sheets of [Co(BTEC)(H2O)3]2-n.