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
Autor: | Carola Schulzke, Alexander Döring, Prinson P. Samuel, Silke Leimkühler, Kajsa G. V. Havelius, Sebastian Horn, Stefan Reschke, Michael Haumann |
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Jazyk: | angličtina |
Rok vydání: | 2011 |
Předmět: |
X-ray absorption spectroscopy
DMSO reductase 010405 organic chemistry Ligand Molybdopterin Infrared spectroscopy chemistry.chemical_element 010402 general chemistry 01 natural sciences 0104 chemical sciences Inorganic Chemistry Bond length chemistry.chemical_compound Crystallography chemistry Molybdenum Institut für Biochemie und Biologie Coordination geometry |
Popis: | 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(μ-S)2Mo 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 ν(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 MoVI cofactor of DMSO reductase and the reduced MoIV 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. (Less) |
Databáze: | OpenAIRE |
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