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Issue 11, 2014
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Coordination and conformational isomers in mononuclear iron complexes with pertinence to the [FeFe] hydrogenase active site

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Abstract

A series of six mononuclear iron complexes of the type [Fe(X-bdt)(PR2NPh2)(CO)] (PR2NPh2 = 1,5-diaza-3,7-diphosphaoctane, bdt = benzenedithiolate with X = H, Cl2 or Me and R = Ph, Bn, Cyc or tert-Bu) was prepared. This new class of penta-coordinate iron complexes contains a free coordination site and a pendant base as essential structural features of the [FeFe]-hydrogenase active site. The bidentate nature of the PR2NPh2 ligands was found to be crucial for the preferential formation of coordinatively unsaturated penta-coordinate complexes, which is supported by first principle calculations. IR-spectroscopic data suggest the presence of coordination isomers around the metal center, as well as multiple possible conformers of the PR2NPh2 ligand. This finding is further corroborated by X-ray crystallographic and computational studies. 31P{1H}-NMR- and IR-spectroscopic as well as electrochemical measurements show that the electronic properties of the complexes are strongly, and independently, influenced by the P-substituents at the PR2NPh2 ligand as well as by modifications of the bdt bridge. These results illustrate the advantages of this modular platform, which allows independent and selective tuning through site specific modifications. Potential catalytic intermediates, namely singly reduced and protonated complexes, have been further investigated by spectroscopic methods and exhibit remarkable stability. Finally, their general capacity for electro-catalytic reduction of protons to molecular hydrogen was verified.

Graphical abstract: Coordination and conformational isomers in mononuclear iron complexes with pertinence to the [FeFe] hydrogenase active site

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Publication details

The article was received on 20 Nov 2013, accepted on 07 Jan 2014 and first published on 08 Jan 2014


Article type: Paper
DOI: 10.1039/C3DT53268B
Citation: Dalton Trans., 2014,43, 4537-4549
  • Open access: Creative Commons BY-NC license
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    Coordination and conformational isomers in mononuclear iron complexes with pertinence to the [FeFe] hydrogenase active site

    A. Orthaber, M. Karnahl, S. Tschierlei, D. Streich, M. Stein and S. Ott, Dalton Trans., 2014, 43, 4537
    DOI: 10.1039/C3DT53268B

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