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A Crystallographic and Mo K-Edge XAS Study of Molybdenum Oxo Bis-,Mono-, and Non-Dithiolene Complexes - First-Sphere Coordination Geometry and Noninnocence of Ligands

  • Ten square-based pyramidal molybdenum complexes with different sulfur donor ligands, that is, a variety of dithiolenes and sulfides, were prepared, which mimic coordination motifs of the molybdenum cofactors of molybdenum-dependent oxidoreductases. The model compounds were investigated by Mo K-edge X-ray absorption spectroscopy (XAS) and (with one exception) their molecular structures were analyzed by X-ray diffraction to derive detailed information on bond lengths and geometries of the first coordination shell of molybdenum. Only small variations in Mo=O and Mo-S bond lengths and their respective coordination angles were observed for all complexes including those containing Mo(CO)(2) or Mo(mu-S)(2)Mo motifs. XAS analysis (edge energy) revealed higher relative oxidation levels in the molybdenum ion in compounds with innocent sulfur-based ligands relative to those in dithiolene complexes, which are known to exhibit noninnocence, that is, donation of substantial electron density from ligand to metal. In addition, longer average Mo-S andTen square-based pyramidal molybdenum complexes with different sulfur donor ligands, that is, a variety of dithiolenes and sulfides, were prepared, which mimic coordination motifs of the molybdenum cofactors of molybdenum-dependent oxidoreductases. The model compounds were investigated by Mo K-edge X-ray absorption spectroscopy (XAS) and (with one exception) their molecular structures were analyzed by X-ray diffraction to derive detailed information on bond lengths and geometries of the first coordination shell of molybdenum. Only small variations in Mo=O and Mo-S bond lengths and their respective coordination angles were observed for all complexes including those containing Mo(CO)(2) or Mo(mu-S)(2)Mo motifs. XAS analysis (edge energy) revealed higher relative oxidation levels in the molybdenum ion in compounds with innocent sulfur-based ligands relative to those in dithiolene complexes, which are known to exhibit noninnocence, that is, donation of substantial electron density from ligand to metal. In addition, longer average Mo-S and Mo=O bonds and consequently lower.(Mo=O) stretching frequencies in the IR spectra were observed for complexes with dithiolene-derived ligands. The results emphasize that the noninnocent character of the dithiolene ligand influences the electronic structure of the model compounds, but does not significantly affect their metal coordination geometry, which is largely determined by the Mo(IV) or (V) ion itself. The latter conclusion also holds for the molybdenum site geometries in the oxidized Mo-VI cofactor of DMSO reductase and the reduced Mo-IV cofactor of arsenite oxidase. The innocent behavior of the dithiolene molybdopterin ligands observed in the enzymes is likely to be related to cofactor-protein interactions.show moreshow less

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Metadaten
Author:Prinson P. Samuel, Sebastian Horn, Alexander Döring, Kajsa G. V. Havelius, Stefan Reschke, Silke Leimkühler, Michael Haumann, Carola Schulzke
DOI:https://doi.org/10.1002/ejic.201100331
ISSN:1434-1948 (print)
Parent Title (English):European journal of inorganic chemistry : a journal of ChemPubSoc Europe
Publisher:Wiley-VCH
Place of publication:Weinheim
Document Type:Article
Language:English
Year of first Publication:2011
Year of Completion:2011
Release Date:2017/03/26
Tag:Bioinorganic chemistry; Enzyme models; Molybdenum; Noninnocence; X-ray absorption spectroscopy
Issue:28
Pagenumber:13
First Page:4387
Last Page:4399
Funder:Deutsche Forschungsgemeinschaft (DFG) [IRTG1422, SCH1480/3-2, Ha3265/3-1]; Wenner-Gren Foundation; Unicat Cluster of Excellence (Berlin); "Bengt Lundqvist Minne"
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Biochemie und Biologie
Peer Review:Referiert