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

Abstract

Keywords: Molybdenum / Enzyme models / X-ray absorption spectroscopy / Noninnocence / Bioinorganic chemistry 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) 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

Interligand communication in a metal mediated LL′CT system – a case study

“…The C8-C9 bond length of 6 was consistent with the C10-C11 bond (1.493Å) and longer than those reported for ene-dithiolate complexes. [21][22][23] These bond distances support that the i Pr 2 Dt 0 remained fully oxidized in 6 in the solid state.…”

Identification of a Bis-molybdopterin Intermediate in Molybdenum Cofactor Biosynthesis in Escherichia coli

“…This is further evidence for the presence of more reduced molybdenum in MoeA. For the MobA ϩ Mo-MPT samples, irrespective of the presence or absence of Mg-GTP, resulting coordination numbers, in comparison with a MoS 4 O model complex (45), consistently revealed only one short MoϭO bond and four Mo-S bonds. This clearly indicates the presence of two MPT units bound to molybdenum in MobA.…”

“…In the case of coordination of molybdenum by oxygen and/or sulfur ligands, this feature is attributable to formally dipole-forbidden 1s34d transitions into * orbitals oriented along Mo-O bond vectors and thus gains intensity for an increasing number of oxygen ligands (44). The pre-edge peak magnitude therefore was particularly large for the molybdate ion (MoO 4 coordination), decreased for MoS 4 O coordination in a synthetic bis-dithiolene model complex (45), and almost absent for MoS 6 coordination in molybdenum disulfide (Fig. 4), revealing a direct dependence of the pre-edge area on the number of oxygen ligands at molybdenum (Fig.…”

An investigation of the Fe and Mo oxidation states in Sr2Fe2−xMoxO6 (0.25⩽x⩽1.0) double perovskites by X-ray absorption spectroscopy

“…Comparison of the spectra from Sr 2 FeMoO 6 and FeO indicates that feature A is linked to the presence of Fe 2+ while the link between the oxygen deficiency and the intensity of feature A 0 is corroborated by comparison of the spectra from SrFeO 2.75 (CN < 6) and Sr 2 Fe 2 O 5 (average CN = 5). appears to be related to the Mo content in Sr 2 Fe 2Àx Mo x O 6 [55][56][57][58]. When x = 0.25 in Sr 2 Fe 2Àx Mo x O 6 , this feature is muted, while for higher values of x, the intensity of feature D increases.…”