An ab initio study of the structural, vibrational and electronic properties of some tetrel-bonded complexes of methane and tetrafluoromethane

Abstract

The binary complexes of ammonia, water, hydrogen fluoride, phosphine, hydrogen sulphide and hydrogen chloride, as electron donors, with methane and tetrafluoromethane, as electron acceptors, have been studied by means of ab initio molecular orbital theory. The properties of interest are the molecular structures, interaction energies and vibrational spectra of the complexes, and the interactions of the molecular orbitals which result in the formation of the complexes. The adducts were found to fall into a number of structural types, including tetrel-bonded, hydrogen-bonded, halogen-bonded, pnicogen-bonded and chalcogen-bonded, depending on the particular combination of electron donor and acceptor. The complexes, irrespective of the type of interaction, were found to be uniformly very weakly bound. The results have been rationalized in terms of the properties of the donors and, together with the conclusions of previous studies involving methyl fluoride, difluoromethane and fluoroform, with the extent of fluorine substitution in the parent molecule, methane.