Synthesis, crystal structure, spectroscopic investigations, thermal behavior and DFT calculations of pentacarbonyl(2-methylpyrazine)chromium(0)

Pentacarbonyl(2-methylpyrazine)chromium(0) [Cr(CO)5(2mpyz)], complex was isolated from its n-hexane solution as orange plate-like crystals which were characterized by IR, NMR spectroscopies and X-ray crystallography. The crystallographic results show that the complex was crystallized in the monoclinic system with the unit cell parameters of a = 7.176 (5), b = 12.045 (3), c = 14.461 (3) Å, β = 90.44 (3)° and space group 2/M. The single crystal structure of the complex shows the bonding of chromium metal to 2-methylpyrazine through the less sterically hindered nitrogen-4 lone pair. The pyrazine ring plane makes an angle of 179.58° (19) with COCrN bond axis. The four carbonyl groups are slightly bent away from pyrazine with the angle of 91.28° (17) for C5CrN1 bond axis. The DFT calculations run out using the Gaussian 03 PC program show good agreement with the experimental results. The thermal properties of the complex were also investigated by differential thermal analysis and thermogravimetry techniques.

The ORTEP-3 view of the whole of the pentacarbonyl(2-ethylpyrazine)chromium(0) molecule showing the atom numbering scheme and the crystal packing projected onto bc plane and onto ab plane are given.Figure optionsDownload as PowerPoint slideHighlights
► Single crystal structure of pentacarbonyl(2-methylpyrazine)chromium(0).
► Spectroscopic investigations of pentacarbonyl(2-methylpyrazine)chromium(0).
► DFT structural analysis are in a good agreement with the experimental results.
► The B3PW916-311+G(2dp) basis set is the best method for the DFT analysis.