Second sphere coordination in anion binding:: Synthesis and spectroscopic characterisation of [trans-Co(en)2Cl2]X (X=SCN or N3).: Single crystal X-ray structure determination and packing of [trans-Co(en)2Cl2]N3

In an effort to explore [trans-Co(en)(2)CI2](+) as anion receptor for linear thiocyanate and azide ions, green coloured microcrystal line [transCo(en)(2)Cl-2]SCN I and single crystals of [trans-Co(en)(2)Cl-2]N-3 II have been obtained by slowly mixing the separately dissolved trans dichlorobis(ethylenediamine)cobalt(III) chloride with ammonium thiocyanate and sodium azide respectively in aqueous medium in 1:1 molar ratio. The newly synthesised complex salts were characterised on the basis of elemental analysis and spectroscopic techniques (IR, UV/vis, H-1 and C-13 NMR). Single crystal X-ray structure determination of II revealed that it crystallizes in the triclinic space group P (1) over bar with a= 6.293(1) angstrom, b=6.696(l) angstrom, c = 7.116(1) angstrom, alpha = 94.02(1)degrees, beta = 11 1.42(1)degrees, gamma = 99.86(1)degrees, V = 272.13(7) angstrom(3), Z= 1, R = 0.0183. Supramolecular hydrogen bonding networks between ionic groups: nitrogen atoms of azide group and NH groups of coordinated ethylenediamine molecules, i.e. N-(HN)-N-... interactions by second sphere coordination besides electrostatic forces of attraction have been observed which probably exist in case of thiocyanate also. This suggests that [trans-Co(en)(2)Cl-2](+) is a promising anion receptor for the linear ions SCN- and N-3(-). The solubility product measurements indicate that the affinity of cationic cobaltammine [trans-Co(en)(2)CI2](+) is greater for azide ion than thiocyanate ion. (c) 2005 Elsevier B.V. All rights reserved.