Molecular Structure of the Molybdenum Oxo-Diperoxo Compound MoO(O₂)₂(OPy)(H₂O):  A Computational and X-ray Study

We have carried out a combined experimental and theoretical study of the molecular structure of the MoO(O₂)₂(OPy)(H₂O) coordination compound using X-ray crystallography and DFT-B3LYP computational method, respectively. The MoO(O₂)₂(OPy)(H₂O) complex crystallizes in the orthorhombic space group Pmna with Z = 4, a = 6.9001(9) Å, b = 8.0471(1) Å, c = 16.227(2) Å, V = 901.0(2) ų, and the X-ray data analysis yields a bipyramidal-pentagonal coordination polyhedron for the Mo atom. The pyridine N-oxide (OPy) ligand occupies the equatorial position, with the oxygen atom of this ligand being located in the same plane as the four peroxo oxygen atoms. The H₂O ligand is situated trans to the oxo group, forming intermolecular hydrogen bonds with peroxo groups belonging to two adjacent complexes. In our theoretical approach these intermolecular interactions were taken into account by including two methanol molecules which form hydrogen bonds with the water ligand leading to a good agreement between the calculated and the experimental geometry. Our results suggest that it is necessary to take into account the presence of these interactions in order to reconcile the theoretical results to the experimental data, in particular the distance between Mo and the oxygen of water ligand. These results seem to be a general feature for analogous bis-peroxo complexes that have been reported in the literature.