Structural and energetic properties of haloacetonitrile - GeF4 complexes

The 1:1 and 2:1 complexes of FCH2CN and ClCH2CN with GeF4 have been investigated by M06/aug-cc-pVTZ calculations, low-temperature, thin-film IR spectroscopy, and an x-ray structure has been obtained for (FCH2CN)(2)-GeF4. Theoretical structures and binding energies for FCH2CN-GeF4 and ClCH2CN -GeF4 demonstrate that halogen substitution significantly weakens the Ge-N dative bonds. The Ge-N distances for the F-and Cl-complexes (2.447 and 2.407 angstrom, respectively) are about 0.2 angstrom longer than in CH3CN-GeF4, and the binding energies (6.5 and 6.9 kcal/mol) are 2-3 kcal/mol less. Furthermore, the Ge-N potential curves are flatter for the halogenated complexes, exhibit a greater response to dielectric media, and thus these systems are more prone to structural change in condensed-phases. For the 2:1 complexes, experimental and theoretical structure and frequency data are consistent with differences in the (calculated) gas-phase and solid-state structures. For (FCH2CN)(2)-GeF4 the calculated gas-phase structure has Ge-N distances about 0.3 angstrom longer those in the x-ray structure (2.366 angstrom vs. 2.059 angstrom Cave)). Also, low-temperature IR spectra of CH3CN/GeF4, FCH2CN/GeF4, and ClCH2CN/GeF4 thin films are consistent with the presence of 2:1 nitrile:GeF4 complexes, and the splitting patterns of the GeF-stretching bands (similar to 700 cm(-1)) match predictions for the corresponding complexes, but are red-shifted relative to the gas-phase predictions, and reflect Ge-N bonds that are compressed in the solid-state, relative to predicted gas-phase structures. (C) 2016 Elsevier B.V. All rights reserved.