Synthesis, Structure and Magnetism of Homologous Series of Polycrystalline Cobalt Alkane Mono-and Dicarboxylate Soaps

摘要

Carboxylate-bridged chain complexes of Co~(II) (the diaquacobalt(II) mono- and #alpha#,#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, [Co{CH_3(CH_2)_(10)-COO}_2(H_2O)_2] and [Co{CH_3(CH_2)_(18)-COO}_2(H_2O)_2], have been solved by X-ray powder diffraction and selectedarea 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)A , #beta#=96.70(3)deg, z=4; and monoclinic, P2_1/a;a=9.7260(7), b=7.5477(7), c=57.53.(1) A, #beta#=94.66(4)deg, 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 A apart, thus confirming the rare anti-anti conformation mode of the #mu#-RCOO groups recently proposed for diaquacobalt(II) #alpha#,#omega#-dodecanedioate. Extensive agnetic characteriation allowed estimation of the feeble antiferromagnetic coupling, which is weaker in the mono-than in the dialkanoate series.