Synthesis, structure and magnetism of homologous series of polycrystalline cobalt alkane mono- and dicarboxylate soaps

Carboxylate-bridged chain complexes of Co(II)l (the diaquacobalt(II) mono- and a,omega-dialkanoates) form two homologous series of layered compounds which have been fully characterised both structurally and magnetically. The crystal structures of two selected members. [CoCH3(CH2)10-COO(2)(H2O)(2)] and [CoCH3(CH2)(18)-COO(2)(H2O)(2)]. have been solved by X-ray powder diffraction and selected-area electron diffraction methods. and refined by the Rietveld technique. Crystal data: monoclinic. P2(1)/a: a 9.688(1) b = 7.5495(9), c = 37.281(5) Angstrom, beta = 96.70(3)degrees. Z=4 and monoclinic. P2(1)/a a = 9.7260(7). b 7.5477(7), C = 57.53(1) Angstrom, beta = 94.66(4)degrees, Z = 4, respectively. Their isomorphous structures contain layers of octahedral diaquacobalt(II) ions bonded to two chemically inequivalent alkanoates one chelating and one bridging two Co atoms about 6.3 Angstrom apart. thus confirming the rare anti-anti conformation mode of the mu-RCOO groups recently proposed for diaquacobalt(II) a,omega-dodecanedioate. Extensive magnetic characterisation allowed estimation of the feeble antiferromagnetic coupling which is weaker in the mono- than in the dialkanoate series.