Mason, W. Roy
M.S. (Master of Science)
Department of Chemistry
Metal ions; Halogens; Complex ions
Few investigations into the nature of simple two-coordinate linear dihalo metal complexes have been previously reported. Consequently, little is known about the electronic structure and bonding in these complexes. Therefore, detailed spectral studies of [(n-C4H9)4N][AuX2] (X = Cl-, Br-, and I-), HgX2 (X = Cl-, Br-) and [(n-C4H9)4N][CuX2] (X = Cl- or Br-) were undertaken to provide an experimental basis for electronic structural models. Following the synthesis of the AuX2- compounds, solution spectra and magnetic circular dichroism (MCD) spectra were obtained in acetonitrile. In addition, thin crystalline samples of these on quartz plates were used to obtain spectra at 300 K and 26 K. The low temperature studies provided enhanced resolution. Absorption spectra were also obtained for cyclohexane solutions of the HgX2 compounds. MCD spectra could not be obtained for these compounds because of low solubility in cyclohexane. Absorption spectra are also reported for thin crystalline films of the CuX2 complexes. Solution studies were complicated by failure of Beer's Law in most suitable solvents. The Au C12- spectra are interpreted in terms of parity-forbidden 5d -> 6s and parity-allowed 5d -> 6p transitions, while the spectra of AuBr2- and Aul2- exhibit in addition ligand to metal charge transfer (LMCT) transitions. Spin-orbit considerations for AuI2- are included since these become important for I- as a ligand. In contrast, the solution and vapor phase absorption spectra for the HgX2 complexes exhibit only LMCT bands. The solid state spectra for both CuC12- and CuBr2- show intense bands assigned to d -> p transitions, although the CuBr2- spectra also exhibit spin-allowed and spin-forbidden LMCT bands. These assignments were made by comparison of trends involving d -> p and LMCT behavior. The results for the Au(I) complexes are discussed in terms of gold orbital participation in bonding. It is concluded that the 5dz2 orbital plays only a small part in sigma bonding, and that the main contributions to bonding in Au(I) two-coordinate complexes rest mainly with the empty 6s and 6p orbitals on Au. Contributions from halide ->5d ii bonding were found to be insignificant.
Koutek, Mary E., "Electronic structure and spectra of linear dihalo complexes of ndÂ¹â�° metal ions" (1979). Graduate Research Theses & Dissertations. 2837.
Northern Illinois University
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