Abstract
Synthetic complexes containing a cis-[MoO2]2+ core are well-established models for the molybdenum co-factor (Moco). Here we report the crystal structure of such a model complex bearing a tetra-dentate amine bis-(phenolate) ligand with fluorine substituents on the phenolate rings, namely, [2,2'-({[2-(di-methyl-amino)-eth-yl]aza-nedi-yl}bis-(methyl-ene))bis-(4,6-di-fluoro-phenolato)]dioxidomolybden-um(VI)), [Mo(C18H18F4N2O2)O2]. Distortion from idealized octa-hedral symmetry about the Mo center is evident in the large O=Mo=O angle [108.54 (4)°] and the small N-Mo-Ophenolate angles [79.79 (4), 81.21 (3), 77.83 (3), and 84.59 (3)°]. The dihedral angle between the phenolate rings is 60.06 (4)°, and π-π stacking is observed between aromatic rings related by inversion (1-x, 1-y, 1-z). The lower data-collection temperature of 150 K vs room-temperature data collection reported previously [KOWXIF; Cao et al. (2014 ▸). Transit. Met. Chem. 39, 933-937] and larger 2θ range for data collection (5.8-66.6° versus 6-54.96°) led to a structure with lower R 1 and ωR 2 values (0.019 and 0.049 vs 0.0310 and 0.0566 for KOWXIF). Comparison of the metrical parameters with KOWXIF suggests that this dataset offers a more realistic depiction of bonding within the MoVI=O moiety.
Highlights
Synthetic complexes containing a cis-[MoO2]2+ core are well-established models for the molybdenum co-factor (Moco)
Comparison of the metrical parameters with KOWXIF suggests that this dataset offers a more realistic depiction of bonding within the MoVI O moiety
The relevance of xanthine oxidase, DMSO reductase, sulfite oxidase to oxygen atom transfer and proton-coupled electron-transfer reactions have driven interest in related mononuclear Mo complexes for generating H2 or expanding opportunities for storage of energy generated by increasingly efficient solar cells
Summary
Molybdenum-containing metalloenzymes are abundant and serve as excellent motivation for biomimetic catalyst development. It is generally accepted that an Mo O bond in the cis-[MoO2]2+ core of DMSO reductase model compounds is formally strengthened (consistent with Mo O) during oxygen atom transfer (Enemark, et al, 2004) Both structures have P1 space-group symmetry, though a, c, , and were different by Æ3 s.u. While the Mo—O(phenolate) and Mo—N bonds in this structure are nearly identical to those reported by Cao et al, the Mo O bond lengths reported here are notably longer than those in KOWXIF and are in line with expectations for related MoVI–oxo species (Enemark, et al, 2004). [Mo(C18H18F4N2O2)O2] 498.28 Triclinic, P1 150 7.3179 (4), 8.0093 (4), 17.5057 (9) 91.8513 (18), 92.9102 (18), 116.6842 (16) 913.82 (8) 2 Mo K 0.79 0.26 Â 0.24 Â 0.15
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