Alkylation of N2S2 nickel(II) complexes /
The nickel complex N,N-bis(2-mercaptoethyl)-1,5- diazacyclooctanenickel(H) (Ni-1) has been the focus of studies es aimed at gaining a better understanding of the reactivity of coordinated thiolates with electrophiles. To an extensive series of four and six-coordinate S-alkylates of N i - 1, benzylat...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Summary: | The nickel complex N,N-bis(2-mercaptoethyl)-1,5- diazacyclooctanenickel(H) (Ni-1) has been the focus of studies es aimed at gaining a better understanding of the reactivity of coordinated thiolates with electrophiles. To an extensive series of four and six-coordinate S-alkylates of N i - 1, benzylation demonstrates an electronic effect on the S-donor ability as well as ligation by the bromide counterion. Addition of two benzyl groups to N i -I produced the six coordinate benzyl thioether complex S,S'- di benzyl- N,N'- bis (2 -mercaptoethyl)- 1,5-diaza cyclooctanedibromonickel(II), [Ni-l-BZ12Br2l. A mixed methyl/benzyl dithioether has been synthesized by the addition of benzyl bromide to [Ni-l-Mel'l-, producing the five coordinatingcomplex-methyl-S'-benzyl-N,N'-bis(2- mercaptoethyl)-I,5diazacyclooctanebromonickel(ll) Iodide, [[Ni-i-BzlMe]Br]l. A comparison of the crystal structures of the dithioether products reveal an impressive expansion in the N2S2 plane cavity as well as a displacement of the nickel(II) ion from the N2S2 plane by 0.43A in the pentacoordinate complex. Electrochemical studies established Ni U/I and Ni,,/',, couples were sensitive both to thioether S substituents (methyl vs. benzyl) and to counterion. N i - 1, N i - 1 *, and sulfursite modified derivatives have suggested that the electron rich character of the complexes is substantially diminished upon addition of electrophiles to the'first thiolate. Kinetic studies established that the nucleophilicity of the second thiolate sulfur towards methylation is ca. 2000 times slower than the first. Efforts to synthesize pentacoordinate nickel complexes in an N2S20 donor environment have led to the isolation and characterization of a series of edier and alcoholic derivatives of N i - I and N i - 1 *. The variation on the coordination number of these complexes (4 vs. 6) may be tuned by control of the interacting ability of the solvent as well as by the choice of counterion. With these ligand environments, only 4 and 6 coordinate complexes were observed. The N,N-bis(2-mercaptoethyl)-1,5-diazacyclooctane ligands can readily be used in formation of a pentacoordinate complex of gallium, Ga-1, for which X-ray crystal structure analysis showed GaH displaced from the N2S2 plane by 0.59 A. |
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| Item Description: | Vita. "Major Subject: Chemistry". In title, numerals and symbols are used. |
| Physical Description: | xiii, 141 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |