title: Structure and vibrational study of the trimethylammonium hexafluorosilicate [(CH3)3NH]2SiF6 compound.
abstract: The X-ray powder diffraction pattern of [(CH(3))(3)NH](2)SiF(6) was obtained and indexed on the basis of a centred cubic unit cell with the P4(1)32 as the likely space group. The Infrared and Raman spectra of this compound have been recorded at room temperature and discussed in relation to the crystal structure. In this salt, the bands corresponding to the cation vibrational modes show that the symmetry of these cations is distorted from the free C(3v) one and that they are strongly hydrogen-bonded to the respective anions. However, the spectra of the anions can be interpreted in term of ordered groups as indicated by the splitting of the bands corresponding to some degenerate vibrational modes. The harmonic frequencies, corresponding to the (CH(3))(3)NH-SiF(6)-NH(CH(3))(3) optimised geometry, were calculated using the SCF semi-empirical MNDO-PM3 method.
authors.affiliation: Laboratoire de Physico-Chimie des Matériaux Inorganiques, Faculté des Sciences, Kenitra, Morocco. lpcmi@yahoo.fr
authors.forename: Ali
authors.initials: A
authors.lastname: Ouasri
authors.forename: Ali
authors.initials: A
authors.lastname: Rhandour
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Dhamelincourt
authors.forename: Paul
authors.initials: P
authors.lastname: Dhamelincourt
authors.forename: Ahmed
authors.initials: A
authors.lastname: Mazzah
mesh_terms: D000838:Anions; D002244:Carbon / Q000737:chemistry; D002412:Cations; D005459:Fluorides / Q000032:analysis* / Q000737:chemistry; D006219:Halogens / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012824:Silicic Acid / Q000032:analysis* / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D000838:Anions; D002412:Cations; D006219:Halogens; D000644:Quaternary Ammonium Compounds; D012824:Silicic Acid; C004832:hexafluorosilicate; D002244:Carbon; D005459:Fluorides