Honors Theses
Date of Award
2005
Document Type
Undergraduate Thesis
Department
Chemistry and Biochemistry
First Advisor
Walter Cleland
Relational Format
Dissertation/Thesis
Abstract
The objective of this project is to prepare Ni(II) coordinate complexes that represent hydrogenase model active sites. The synthetic analog approach provides an effective means to study redox behavior of nickel. Six Ni(II) complexes with the hydrotris(3,5- dimethylpyrazolyl)borate ligand and varying forms of the dithiobenzoate ligand were synthesized through ligand substitution using a novel procedure in the laboratory. Infrared spectrophotometry and elemental analysis show that the synthesis of the complexes was successful. Each Ni(II) complex had the characteristic B-H (boronhydrogen) stretch representative of the hydrotris(3,5-dimethylpyrazolyl)borate ligand at approximately 2500 cm’’ as well as the Ar-H and C=C stretches at 3100-3000 cm’’ and 1600 cm’’, respectively. Both of these are characteristic of the aromatic ring in the dithiobenzoate portion of the complex. Elemental analysis yielded the C:H:N content of each complex. The actual percentages of all compounds (except for TpNiS2CC6H4-p- OCH3) were within 0.4% of the calculated percentages, which confirmed the identity of our complexes. Cyclic voltammetry experiments showed that electrochemical properties of these complexes are solvent-dependent. In MeCN, the reduction of Ni^"^ to Ni reversible, while the oxidation of Ni^"^ to Ni^'*' appeared to be irreversible. In contrast, the oxidation of Ni^"^ to Ni^"^ was reversible in CH2CI2 and the reduction of Ni^^ to Ni irreversible. It was also shown that the substituent groups affect redox potential. Compared to TpNiS2CC6H5, TpNiS2CC6H2-(CH3)3, TpNiS2CC6H4-p-CH3, and TpNiS2CC6H4-/7-OCH3 are easier to oxidize and harder to reduce due to the electron donating capabilities of the substituents. TpNiS2CC6H4-/?-F and TpNiS2CC6H4-jp-Cl, on the other hand, are easier to reduce and harder to oxidize due to the electron withdrawing capabilities of the halogens. In addition, most of the complexes show some degree of reversibility as most of the ia/ic values are around 1.0. TpNiS2CC6H4-;?-Cl shows reversibility in both the reduction and oxidation.
Recommended Citation
Enggano, Brian Matthew, "Synthesis and Characterization of Nickel(II) Coordination Complexes with Hydrotrispyrazolylborato and Dithiobenzoato Ligands" (2005). Honors Theses. 2204.
https://egrove.olemiss.edu/hon_thesis/2204
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