Crystal Structure Analyses of an Organic Charge Transfer Salt, Three Bridged Binuclear Cobalt Complexes, and a Thiazole Derivative.
Date of Award
Doctor of Philosophy (PhD)
Steven F. Watkins
The structures of five compounds have been determined by single crystal x-ray diffraction. A non-superconducting organic charge-transfer salt, bis- (bis-(ethylenedithia)-tetrathiafulvalene) dibromoaurate(I), (BEDT-TTF)$\sb2$AuBr$\sb2$, was synthesized electrochemically, and crystallizes in monoclinic space group P2/c with Z = 2 and lattice constants 9 = 7.7950(21) A, b = 6.7150(6) A, c = 32.2000(31) A, $\beta$ = 100.508(13)$\sp\circ$; R = 0.0365 for 174 variables and 1904 observed reflections. One end of the independent BEDT-TTF molecule is disordered, a crystallographic feature which is common in these salts. Short sulfur-sulfur contact distances between cations are observed; however, the cations are not arranged in the same manner as are those in related superconductors. The structures of three doubly-bridged binuclear cobalt compounds are reported. The first, $\mu$-amido-$\mu$-hydroxo-bis- (bis-(ethylenediamine)cobalt(III)) tetrathiocyanate monohydrate, crystallizes in monoclinic space group P2$\sb1$/a, with Z = 4 and cell constants a = 16.732(4) A, b = 8.698(4) A, c = 19.551(3) A, $\beta$ = 107.79(1)$\sp\circ$; R = 0.0485 for 299 variables and 2573 observed reflections. Coordination about each cobalt is slightly distorted from idealized octahedral geometry. The thiocyanate anions participate in hydrogen bonding with hydrogen atoms from the ethylenediamine nitrogens. The structure of $\mu$-amido-$\mu$-peroxo-bis- (bis-(ethylenediamine)cobalt(III)) trithiocyanate monohydrate was determined at room temperature in 1972. The low temperature (115 K) determination is reported herein. The crystal undergoes an ordering phase transition from Pbca (at 298 K) to P2$\sb1$ca. Lattice constants at 115 K are a = 26.501(7) A, b = 12.641(5) A, c = 14.402(8) A; R = 0.0662 for 508 variables and 5198 observed reflections. Conformational disorder previously reported in two of four ethylenediamine groups of the cation has resolved upon cooling. Remaining disorder is apparent in one thiocyanate anion. 2-(3,3-Dimethyl-1-triazeno)-1,3-thiazole crystallizes in monoclinic space group C2/c, with lattice constants 9 = 11.7831(9) A, b = 11.7362(11) A, c = 11.7663(9) A, $\beta$ = 109.0583(75)$\sp\circ$; R = 0.0525 for 100 variables and 764 observed reflections. The molecule is nearly planar. Strong interactions are observed between molecules, which pack "pancake fashion" in the crystal. The structure of a third cobalt complex $\mu$-bromo-$\mu$-hydroxo-bis- (bis-(ethylenediamine)cobalt(III)) tetrabromide, has been only partially resolved due to apparent disorder in the bridging atom positions. The present model in monoclinic space group C2 exhibits cell parameters of a = 14.430(3) A, b = 8.687(3) A, c = 10.820(4) A, $\beta$ = 121.7(5)$\sp\circ$; R = 0.116 for 93 variables and 1097 observed reflections. Additionally, results are presented of the analysis of an iron-tellurium-oxide system, which has catalytic potential for conversion of butene to butadiene. The sample which displayed catalytic activity was shown to be different from those displaying no such activity: only the catalytically active material contained Fe$\sb2$TeO$\sb6$.
Greene, Andrea Claire, "Crystal Structure Analyses of an Organic Charge Transfer Salt, Three Bridged Binuclear Cobalt Complexes, and a Thiazole Derivative." (1988). LSU Historical Dissertations and Theses. 4640.