An experimental and theoretical vibrational spectroscopic study of [AsPh4]2[Sn(dmit)3]·Me2CO

As shown previously by X-ray structure determinations, [tris(1,3-dithiole-2-thione-4,5-dithiolato)stannate(IV)]2− salts, [Q]2[Sn(dmit)3], contain isolated cations and dianions. While the tin centres generally having octahedral geometries, the overall shapes of the dianions of these complexes in the solid state can differ with conformations varying from T, Y to asymmetrical arrangements. We now report, as a follow up to our earlier study on the Y-shaped complex, [NEt4]2[Sn(dmit)3], an experimental and theoretical study of the vibrational spectra of solid solvated {[AsPh4]2[Sn(dmit)3]·Me2CO}, in which the dianion has a T-shaped conformation. The infrared and Raman spectra, recorded from 4000 to150 cm−1, have been analysed by different ab initio calculations based on restricted Hartree-Fock (RHF) and density functional theory (DFT-Beck3LYP). The calculations were carried out on isolated dianions and cations with the 6-31G and 6-31G(d) basis sets and effective core potentials of Steven, Bash and Krauss (SBK). Fundamentals, overtones and combinations have been assigned. Generally, the Y- and T-shaped dianions exhibit similar infrared/Raman spectra, apart from differences in the CC and the symmetrical M-S stretching frequencies: such differences can be used diagnostically to distinguish the overall shape of the tris(chelated)metallate dianion.