Vibrational and 119Sn Moessbauer spectra and X-ray crystal structure of ammonium tetrafluorodimethylstannate(IV)

Article abstract of DOI:10.1016/0022-328X(94)88107-3

Ammonium tetrafluorodimethylstannate(IV) has been prepared and characterized by IR, Raman and 119Sn Moessbauer spectroscopies.The Moessbauer parameters place this compound at the frontier between the dimethyltin(IV) compounds that gave rise to the quadrupole splitting (OS) vs.C-Sn-C angle correlation, and the dimethyltin(IV) salts of strong protic acids and superacids.The Moessbauer QS, as well as the IR and Raman spectra, indicate that the C-Sn-C angle is 180^o.The IR-active ν(Sn-F) E_u mode appears at 345 cm^-1, and this mode is related to the Moessbauer QS for trans- because strong donors have a negative partial quadrupole splitting (pqs) and weaken the Sn-F bond.The IR spectrum also suggests the existence of normal (not polyfurcated) N-H...F hydrogen bonds.The X-ray crystal structure contains two crystallographically independent centrosymmetric ^2- anions, but only one kind of NH⁺4 cation.The cations and the anions are linked by nearly linear N-H...F hydrogen bonds giving rise to a three-dimensional network.The average Sn-F distance is 2.127 Angstroem and the usefulness of covalent radii to predict accurate bond distances is challenged.An equation to calculate the average Sn-F distance in complexes from the Moessbauer QS is proposed.Key words: Tin; Moessbauer spectroscoopy; Infrared spectroscopy; Raman spectroscopy; Hydrogen bonding; Crystal structure