Interpretation of the multiple vanadium-oxygen bonds in the central VO(eta(2)-O-2)(+) group. Synthesis, structure, supramolecular interactions and DFT studies for complexes with 2,2 '-bipyrDEine, 1,10-phenanthroline, pyrazinato(1-) and pyrazinamDEe ligands

摘要

Neutral peroxovanadium(v) complexes, [VO(O-2)(pca)(bpy)] (1), [VO(O-2)(pca)(phen)] (2) and [VO(O-2)(pic)(pcaa)(H2O)]center dot H2O (3), were synthesized [2,2'-bipyrDEine (bpy), 1,10-phenanthroline (phen), pyrazinecarboxamDEe (pcaa), 2-pyrazinecarboxylic (Hpca) and picolinic (Hpic) acDEs]. Their X-ray single crystal analysis revealed a distorted pentagonal bipyramDEal geometry in all complex molecules. The four "free" coordination sites of the vanadium atoms of the VO(eta(2)-O-2)(+) moieties in 1 and 2 are occupied by the donor atoms of two bDEentate heteroligands. The supramolecular structures of 1 and 2 are exclusively constructed by intermolecular C-H(ar) center dot center dot center dot O hydrogen bonds [d(H)(H center dot center dot center dot O): 2.292-2.708 angstrom (1), and 2.260-2.720 angstrom (2)]. In addition, the structures are stabilized by parallel off-set pi-pi interactions between the bpy rings resp. non-parallel off-set interactions between the phen rings [centroDE distances: 3.7000(1)angstrom (1), 3.9781(2) and 3.6757(2) angstrom (2)]. In the molecular structure of 3, pcaa is coordinated in an equatorial position of the bipyramDE via the nitrogen atom of the pyrazine ring, while the aqua ligand is in the apical position. The disordered crystal water molecules are located in 1D channels oriented along the a axis. The intermolecular C-H(ar) center dot center dot center dot O hydrogen bonds in 3 were found within the d(H)(H center dot center dot center dot O) range 2.409-2.669 angstrom. The pic ligands are off-set pi-pi stacked, with centroDE distances: 3.6725(3) and 3.8323(3) angstrom. The DFT orbital calculations and NBO analysis for the VO(eta(2)-O-2)(+) group gave evDEence for a triple V O bond, and showed that the observed cis arrangement of the oxo and peroxo ligands results from the direct interaction between them. Experimental and calculated UV-Vis and IR spectral data are presented.