Synthesis and properties of a molybdenum Schiff base electrocatalyst for generating hydrogen from acetic acid

Dioxidomolybdenum(VI) complex featuring a 2,4-di-fluoro-substituted amine bis-(phenolate) ligand

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.