Biomimetic Model Compounds of Iron Active-Site of 【Fe】and 【NiFe】Hydrogenases

• Main Authors: Heng-Bin Gau, 高鴻賓
• Other Authors: Wen-Feng Liaw
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/08444366457397599929

碩士 === 國立彰化師範大學 === 科學教育研究所 === 89 === Abstract The pentacoordinate, 16-electron Fe（Ⅱ）complexs【PPN】【Fe（CO）2（CN）（E,NH-C6H4）】（E=Se（1）、Te（2））, stabilized by strong E,N π-donation of chelating 【E,NH-C6H4】2－ligand, were prepared by the reaction of bis-(2-aminopheny）diselenide or bis-(2-aminophenyl）ditelluride and 【PPN】【Fe（CO）4CN】respectively. Protonation of complexes 1 and 2 by electrophiles （2-aminothiophenol and 1,2-benzenedithiol）yielded pentacoordinate, 16-electron Fe（Ⅱ）complex【PPN】【Fe（CO）2（CN）（S,NH-C6H4）】and hexacoordinate Fe（Ⅱ）complex【PPN】2【（CN）（CO）2Fe（μ-S,S-C6H4）】2 respectively。 【PPN】【Fe（CO）3（CN）2Br】（3）was prepared by the reaction of 【PPN】【Fe（CO）4CN】and BrCN . Ligand substution reaction of complex 3 and 2-mercaptopyridine sodium salt, 2-mercaptopyridine N-oxide sodium salt and ethanethiol sodium salt yielded 【PPN】【Fe（CO）2（CN）2 （S，N-C5H4）】（4）、【PPN】【Fe（CO）2（CN）2 （S，O-C5H4N）】（5）and【PPN】2【Fe2（CO）4（CN）4 （SC2H5）2】（6）,individually. Photolysis of THF solution of complex 4 snd 5 under CO led to formation of the coordinate-unsaturated iron（Ⅱ）-dicyanocarbonyl thiolate compounds 【PPN】【（CN）2（CO）Fe（S,N-C6H4）】（K）, the potential iron-site structural and functional model compound of active site of 【NiFe】hydrogenases isolated from D. gigas. The IR νCN streching frequencies and patterns of complexes 4 snd 5 have unambiguously identified two CN－ ligands occupying cis position. In addition , the theoretical calculations support that the architecture of five-coordinate complex K with a vacant site trans to the CO ligand serves as comformational preference. Complex 4 was reobtained when the THF solution of complex K was exposed to CO atomsphere at 25℃. Complex K and Ni-A/Ni-C states【NiFe】hydrogenases from D. gigas. exhibit the similar one-band pattern in theνCO region and two-band pattern in theνCN region individually, but different positons, which may be accounted for by the distinct electronic effects between 【S,N-C6H4】－ and S-cysteine ligands. Also,the facile formations of five-coordinate complex K implicate that the strong σ-donor, weak π-acceptor CN－ ligands play a key role in creating/stabilizing five-coordinate iron（Ⅱ）center with a vacant coordination site.