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 mu-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) Angstrom, respectively. Compound 2, alpha-cis-[Cr(bispicen)(H3O2)]I-2 [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) Angstrom, 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 mu-H3O2 bridges. Compound 1 crystallizes in the monoclinic space group C2/c with a=9.967(1) Angstrom, b=15.020-(3) Angstrom, c=9.909(2) Angstrom, beta=116.81(3)degrees, and Z=4. Compound 2 crystallizes in the monoclinic space group C2/c 21.380(4) Angstrom, b=9.793(1) Angstrom, c=10.220(2) Angstrom, beta=116.69(2)degrees and Z=4.