Sterically encumbered N2S2 complexes of nickel /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1994.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | A new ligand based on 1,5-diazacyclooctane (daco) with an increase in steric hinderance has been synthesized. The ligand N,N$ sp prime$-(bis-2-methyl-$2 $-mercaptopropane)-1,5-diazacyclooctane (bme*-daco) was prepared by the ring opening reaction of isobutylene sulfide with daco (1,5-diazacyclooctane) at the less hindered carbon in 65% yield. The nickel complex (bme*-daco)Ni, 1*, is attained by the instantaneous reaction with Ni(acac)$ sb2$ in toluene in good yield. The X-ray crystal structure of complex 1* demonstrated the increase of steric bulk on one face of the square planar Ni$ sp{ rm II}$, in essence creating a hydrophobic pocket. Complex 1* was designed with tertiary sulfurs in an attempt to stabilize possible intermediates observed in the chemistry of the complex (bme-daco)Ni, 1, with oxygen in water. Unlike 1, complex 1* reacts slowly with oxygen in water, but S-oxygenates are readily produced with hydrogen peroxide as the source of oxygen atoms. The goal of isolating intermediate levels of S-oxygenation by the use of steric encumbrance was accomplished in an impressive fashion; for the first time a nickel bound sulfenate (Ni-S(O)R) was isolated upon oxidation with hydrogen peroxide. In this fashion, the monosulfenate 4*, the bissulfenate, 5*, and the mixed sulfenate-sulfinate, 6* complexes were isolated and characterized. In addition to sulfenates, the monosulfinate, 2*, and the bissulfinate, 3*, were also obtained. The chemical reactivity of (bme*-daco)Ni complex 1*, was dominated by the thiolate sulfurs as demonstrated by the reaction of 1* with organic electrophiles such as methyl iodide to produce the mono- and dimethylated cationic thioethers 10* and 8*, respectively in high yields. In addition, macrocycles based on 1 and 1* were prepared taking advantage of the template effect of the cis-coordinated thiolates and with the intention of forcing a square pyramidal geometry. Thus the N$ sb2$S$ sb2$O complexes of both 1 and 1* were found to have different coordination numbers and geometry around the nickel atom. This difference is caused by the increase steric encumbrance of the methyls in 1*. |
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| Item Description: | "Major subject: Chemistry." In title, numerals are subscript. Vita. |
| Physical Description: | xv, 125 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |