Small molecule models of [NiFe] H₂ASE active sites /
X-ray crystal structures confirm and delineate the icrofilm Inc. ability of the cis-dithiolate sulfur sites of (N,N'-Bis(2-mercaptoethyl)-1,5-diazacyclooctanato]nickel(II), Ni-1, to bind both iron(0) and iron(II) carbonyls forming robust Ni-Fe heterometallics. These molecules provide the first...
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1998.
|
| Subjects: |
| Summary: | X-ray crystal structures confirm and delineate the icrofilm Inc. ability of the cis-dithiolate sulfur sites of (N,N'-Bis(2-mercaptoethyl)-1,5-diazacyclooctanato]nickel(II), Ni-1, to bind both iron(0) and iron(II) carbonyls forming robust Ni-Fe heterometallics. These molecules provide the first well-characterized examples of iron carbonyl units sulfur-bridged to nickel, and provide precedents for the heterometallic Ni-Fe site found in the x-ray crystal structure of Desulfovibrio gigas (NiFe]hydrogenase. In the NiFe heterobimetallics synthesized here, the most significant feature of cyclic voltammograms in the cathodic potential region is predominately attributed to the Nill; couple in the Ni-l unit. The thiolate-bridged ironcarbonyl unit serves as a soft ligand set to ease the Nill; redox couple of the thiolate sulfur-rich Ni center. The observation of nearly identical infrared spectra in the diatomic region of the oxidized forms (Ni-A and Ni-B) of [NiFe] [] and [], including isotopic label shifts, indicates that the [] donor set has the same electronic effect on pyramidal Fe(CN)2(CO) and promotes further development of the organometallic model complexes as a spectroscopic reference. For a series of 9 complexes [], which cover a broad range of electronic effects (as confirmed by electrochemical studies) within a constant hexa-coordinate structure and medium (MeCN), the shifts of v(CO) and v(CN) stretching modes are affected in the same manner. The enzyme states that are not in the catalytic cycle fit the correlation of v(CO) and v(CN) of the model complexes and are expected to maintain hexa-coordinate about iron. The electrochemical studies of the myel complexes demonstrate a positive [] couple and/or a very negative [] couple and indicate that the redox active site in [] [] is not at iron. The S-based nucleophilicity of Ni-; is successfully extended by the eleceophilic attack of PhSe+. The isolation of [] provides an rare example (only the second to date) of a S-bound metallo-selenenylsulfide complex. The H+- promoted disproportionately of the [] bond on Ni-bound selenenylsulfide complex produces bisdisulfide and Phseseph with the loss of the Ni2+ ion. This work presented the first opportunity to isolate and identify the oxidized ligand as an intermolecular a disulfide for the stoically rigid bme-daco ligand system. |
|---|---|
| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xvi, 160 leaves : illustrations ; 28 cm. |
| Bibliography: | Includes bibliographical references (leaves 115-122). |