Structural, energetic, and vibrational properties of the homodimers of the silyl, germyl, and stannyl halides, (MH3X)2 (M=Si, Ge, Sn; X=F, Cl, Br, I)

A number of properties of the homodimers of the three families of molecules MH3X, where M is Si, Ge, and Sn and X is F, Cl, Br, and I are computed. The results are compared with those of a similar study of the homodimers of the methyl halides containing the same four halogen atoms, and some notable differences are observed among related sets of monomer species. The interaction energies, the primary intermolecular geometrical parameters, the changes in the intramolecular bond lengths, and the vibrational data (wavenumber shifts and dimer/monomer infrared intensity ratios) of some of the modes most closely associated with the site of interaction show, for the most part, regular variations as the central atom and the halogen atom are systematically varied. The results are interpreted in terms of the changes in the bonding properties of the monomer molecules as they undergo dimerization.