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

Abstract

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 Å, 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) Å; β = 98.01(4)° 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_α atom than is the C–C–Ti skeleton in the titanium compound C₂H₅TiCl₃.