Syntheses,X-ray structure,emission and vibrational spectroscopies,DFT and thermogravimetric studies of two complexes containing the bidentate ligand 5-phenyl-1H-pyrazol-3-yl)methyl) phosphine oxide

Abstract

The coordination chemistry of (diphenyl((5-phenyl-1H-pyrazol-3-yl)methyl) phosphine oxide), 1, was explored. Reacting appropriate equivalents of this ligand and either cobalt perchlorate or MoO₂Cl₂ results in formation of [Co((C₆H₅)₂POCH₂(C₃N₂H₂)(C₆H₅))₂(C₄H₈O)₂][ClO₄]₂, 2, and MoO₂Cl₂((C₆H₅)₂POCH₂(C₃N₂H₂)(C₆H₅))(THF), 3. Complexes were characterized by FTIR, NMR, TGA and elemental analyses. Single crystal X-ray spectroscopy reveals octahedral geometries for both compounds. Complex 2 consists of two trans THF ligands in axial positions and two (diphenyl((5-phenyl-1H-pyrazol-3-yl)methyl) phosphine oxide) ligands occupying equatorial positions resulting in an overall octahedral geometry. Two perchlorate counter anions complete the structure. The Co ion resides on an inversion point. THF contains disorder with the four carbon atoms and the major orientation refined to an occupancy of 86.1(9)%. Complex 3 consists of the cis-dioxo MoO₂ unit bonded with axial trans-chloride ligands and 1 in the equatorial plane completing the disordered octahedral geometry. A THF ligand is hydrogen bonded to the H-atom on the nitrogen of the pyrazole moiety in ligand 1. DFT calculations based on geometries obtained crystallographically were useful in assigning FTIR peaks and the UV-vis spectra.