Conformational Structures of Solvated Co(II) Ions in Amides and Trimethyl Phosphate Studied by X-Ray Diffraction and Isomorphous Substitution

Author: Yokoyama Haruhiko   Nakajima Kousuke  

Publisher: Springer Publishing Company

ISSN: 0095-9782

Source: Journal of Solution Chemistry, Vol.33, Iss.6-7, 2004-06, pp. : 607-629

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Abstract

Conformational structures of solvated cobalt(II) ions in several amides and trimethyl phosphate (TMP) have been studied by the X-ray diffraction method using the isomorphous substitution technique. The amides used are formamide (FA), N-methylformamide (NMF), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and N,N-dimethylpropioamide (DMPA). From the analysis of radial distribution functions around Co2+, the distances from Co2+ to each atom of coordinated solvent molecules were obtained and the coordination numbers were determined to be six, except for DMPA where four-coordinate species coexist. The Co{\bond}O bond distances are 2.09(1)–2.11(1) Å for six-coordinate species but is 1.96(2) Å for the four-coordinate species. In the amide solutions the Co{\bond}O{\bond}C bond angles are 126(3)° (FA), 123(2)° (NMF), 123(2)° (DMF), 134(3)° (DMA), and 137(4)–138(4)° (DMPA). The Co{\bond}O{\bond}C{\bond}N dihedral angles were also estimated to discuss the conformational distortion on the Co2+-amide interactions. For TMP solutions the Co{\bond}O{\bond}P angle was determined to be 150(4)°, and the conformational structure on the Co2+–TMP interaction is discussed.