Structure and vibrational properties of ethyltrioxorhenium(VII), C2H5ReO3, investigated by gas electron diffraction, single crystal X-ray diffraction, IR spectroscopy and quantum chemical calculations

The electron diffraction pattern of gaseous ethyltrioxorhenium(VII) has been analysed in terms of a C2H5ReO3 molecule with C-s symmetry overall. Least-squares refinement yields the following dimensions (r(a) in Angstrom, angles in deg): Re-C 2.095(6), C-C 1.530(16), Re-O 1.711(2), C-H 1.106(13), Re-C-C 112.0(9), and O-Re-C 104.6(5). The compound forms monoclinic crystals [a = 6.421(3), b = 5.111(2), c = 15.108(5) Angstrom; beta = 98.01(4)degrees at 150 K] composed of discrete molecules little different dimensionally from the gaseous species. Both the structure and IR spectrum of the molecule isolated in an Ar matrix are well reproduced by density functional theory (DFT) calculations. There is no hint of anything unusual about the geometry of the C2H5Re fragment, but the C-C-Re skeleton is appreciably stiffer to bending at the C atom than is the C-C-Ti skeleton in the titanium compound C2H5TiCl3.