AN EXAFS SPECTROSCOPIC STUDY OF SOLVATES OF COPPER(I) AND COPPER(II) IN ACETONITRILE, DIMETHYL-SULFOXIDE, PYRIDINE, AND TETRAHYDROTHIOPHENE SOLUTIONS AND A LARGE-ANGLE X-RAY-SCATTERING STUDY OF THE COPPER(II) ACETONITRILE SOLVATE IN SOLUTION

X-ray absorption edge and EXAFS spectra of the acetonitrile, dimethyl sulfoxide, pyridine and tetrahydrothiophene solvated copper(I) ions and the acetonitrile and dimethyl sulfoxide solvated copper(II) ions have been measured in solution. Analysis reveals that the copper(I) solvates are most probably tetrahedral, and the following Cu-solvate bond distances have been found: Cu-N = 1.99(2) angstrom in acetonitrile, Cu-O = 2.09(4) angstrom in dimethyl sulfoxide, Cu-N = 2.06(1) angstrom in pyridine, and Cu-S = 2.30(1) angstrom in tetrahydrothiophene. The copper(II) solvates are most probably Jahn-Teller distorted octahedrons, and the following equatorial Cu-solvate bond distances have been found: Cu-N = 1.99(1) angstrom in acetonitrile, and Cu-O = 1.98(1) angstrom in dimethyl sulfoxide. An 1.0 M solution of copper(II) trifluoromethanesulfonate in acetonitrile has been studied by means of the large-angle X-ray scattering technique, and the following Cu-N and Cu-C distances have been found for the Cu(CH3CN)42+ complex: 1.99(1) and 3.12(1) angstrom, respectively. No solvate molecules in the axial positions could however be seen by any of the techniques used. The structure of the tetraaquacopper(I) ion has been assumed to be tetrahedral, and from a correlation between the difference in bond length between the copper(I) and copper(II) solvates and the disproportionation constants of copper(I) in the solvent, the Cu-O bond distance is predicted to be approximately 0.14 angstrom longer than the equatorial Cu-O distances in the Jahn-Teller distorted hexaaquacopper(II) complex, thus about 2.13 angstrom.