Models of the iron-only hydrogenase enzyme: structure, electrochemistry and catalytic activity of Fe-2(CO)(3)(-dithiolate)(,(1),(2)-triphos) 机翻标题: 暂无翻译,请尝试点击翻译按钮。

Dalton transactions: An international journal of inorganic chemistry
2019 / 48 / 18
UCL, Dept Chem, 20 Gordon St, London WC1H 0AJ, England;UCL, Dept Chem, 20 Gordon St, London WC1H 0AJ, England;UCL, Dept Chem, 20 Gordon St, London WC1H 0AJ, England;Univ North Texas, Dept Chem, 1155 Union Circle,Box 305070, Denton, TX 76203 USA;UCL, Dept Chem, 20 Gordon St, London WC1H 0AJ, England;Kings Coll London, Dept Chem, Britannia House,7 Trinity St, London SE1 1DB, England;
Unwin, David G.;Ghosh, Shishir;Ridley, Faith;Richmond, Michael G.;Holt, Katherine B.;Hogarth, Graeme;
A series of diiron bis(2-diphenylphosphinoethyl)phenylphosphine (triphos) complexes Fe-2(CO)(3)(-dithiolate)(,(1),(2)-triphos) (1-4) [dithiolate = 1 pdt; 2 edt; 3 adt (R = Bz), 4 (SMe)(2)] have been prepared and investigated as biomimics of the diiron site of [FeFe]-hydrogenases. The triphos ligand bridges the diiron vector whilst also chelating to one iron and 1-3 exist as a mixture of basal-basal-apical (bba) and basal-basal-basal (bbb) isomers which differ in the mode of chelation. In solution the bba and bbb forms do not interconvert on the NMR time scale, but the bba isomers are fluxional, and at low temperature four forms of 1bba are seen as the conformations for the pdt ring and triphos methylene groups are frozen. Crystallographic studies have established bba (pdt) and bbb (adt) ground state conformations and in both there is a significant deviation away from the expected eclipsed conformation (L-ap-Fe-Fe-L-ap torsion angle 0 degrees) by 49.4 and 24.9 degrees respectively, suggesting that introduction of triphos leads to significant strain and DFT calculations have been used to understand the relative energies of isomers. The electron rich nature of the diiron centre in 1-4 would suggest rapid protonation, but while bridging hydride complexes such as [Fe-2(CO)(3)(-pdt)(,(1),(2)-triphos)(-H)][BF4] (1H(+)) can be formed the process is slow. This behavior is likely a result of the high energy barrier in forming the initial (not observed) terminal hydride which requires a significant conformational change in triphos coordination. CV studies show that all starting compounds oxidize at low potentials and the addition of [Cp2Fe][PF6] to 1 affords [Fe-2(CO)(3)(-pdt)(,(1),(2)-triphos)][PF6] (1(+)) which has been characterised by IR spectroscopy. DFT studies suggest a ground state for 1(+) with a partially rotated Fe(CO)(2)P moiety that yields a weak semi-bridging carbonyl with the adjacent Fe(CO)P-2 group. No reduction peaks are seen for 1-4 within the solvent window