Chain-Structured cis-Hydroxoaquachromium(III) Complexes and Their Magnetic Properties

Antiferromagnetic coupling between chromium(III) atoms was found to exist in two cis-hydroxoaquachromiu(III) complexes, having a chain structure with μ-H₃O₂^- bridges. Compound 1, trans-[Cr(Py)₂(H₃O₂)₂]Cl (Py = pyridine), consists of infinite chains of Cr(III) ions bridged by two H₃O₂^- units with Cr···Cr and O···O separations of 5.2073(5) and 2.422(2) Å, respectively. Compound 2, α-cis-[Cr(bispicen)(H₃O₂)]I₂ [bispicen = N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine], consists of infinite chains of Cr(III) ions bridged by one H₃O₂^- unit with Cr···Cr and O···O separations of 5.6328(6) and 2.428(5) Å, respectively. The exchange coupling constants, J = -1.31 cm^-1 in 1 and J = -0.47 cm^-1 in 2, were obtained by magnetic susceptibility measurements between 2 and 81 K. These values indicate intrachain antiferromagnetic interactions, mediated by hydrogen bonding through μ-H₃O₂ bridges. Compound 1 crystallizes in the monoclinic space group C2/c with a = 9.967(1) Å, b = 15.020(3) Å, c = 9.909(2) Å, β= 116.81(3)°, and Z = 4. Compound 2 crystallizes in the monoclinic space group C2/c with a = 21.380(4) Å, b = 9.793(1) Å, c = 10.220(2) Å, β= 116.69(2)° and Z = 4.