Far-infrared, Raman, and Mössbauer spectra of trihalogenostannate(II) complexes, [SnX₃]^–, [SnX₂Y]^–, and [SnXYZ]^–, with different cations

Abstract

All ten of the binary and mixed trihalogeno-complexes of tin(l1).[SnXYZ] -(X, Y, or Z = CI, Br, or I), have been prepared as salts of one or more of the cations [Et,N]+, [Bun,N]+, and [Ph,As]+.Their far4.r. (to 80 cm-l) and Raman spectra show that discrete pyramidal trihalogeno-anions are present in solution. This structure is retained in the solid state for the [Bu",N]+ salts, but with [Ph,As]+ and [Et,N]+ cations there is increasing solid-state interaction resulting in a lowering of symmetry. This is shown also by the WSn Mossbauer data. For salts of a given cation, the isomer shifts show a regular variation with the sums of the electronegativities of the halide ligands. Quadrupole splitting was observed in each case, and showed an inverse relationship to the isomer shifts in each series ; this is most readily interpreted as a consequence of a quadrupole splitting-electronegativity correlation.The species absorbed by an anion-exchange resin in the halide (X-or Y-) form from SnX,-HX solutions (X or Y = CI, Br, or I) are shown to be [SnXJ-or [SnX,Y]-, and not [SnX,I2-as previously reported for X = CI.PREVIOUS studies on trifluorostannates(11) have indicated that with some cations, anion-association takes place in the solid state.lP2 With tribromo-and tri-iodostannates(I1) the vibrational spectra show that with such large cations as [Ph,As]+ the anion is three-coordinate but has lower symmetry than C, , unlike the chloro-analogue^.^ The few data available at the commencement of this work ** suggested that the Mossbauer parameters of halogeno-anions of tin (11) are also dependent upon the cation. It was therefore of interest to investigate in more detail the influence of cations on the vibrational and Mossbauer spectra of solid trihalogenostannate(I1) salts.The cations chosen for this study were such that

Cationic Cryptand Complexes of Tin(II)

“…The less shielded signal, with an isotropic shift of 165 ppm, is assigned to the tribromidostannate anion . In this case, the anion site falls slightly short of perfect axial symmetry (κ = 0.95), consistent with slight deviations from C 3 v symmetry observed in the structure of this anion . The isotropic shift of the more shielded signal is similar to that of 10 (δ iso −920) and exhibits no specific symmetry (κ = 0.7).…”

“…The isotropic shift differs from that reported for 5 ; however, the experiment was performed at a much lower spinning speed (11 kHz versus 17 kHz), leading to the possibility of temperature effects. The assignment was confirmed by preparing the anion independently as the [NBu 4 ][SnCl 3 ] salt . The 119 Sn SSNMR spectrum of the ammonium salt closely resembles the less shielded signal of the complex (Supporting Information, Figure S5).…”

“…The downfield signal differed considerably from the analogous signal assigned to the anion of 12 . While the isotropic shift of the downfield signal initially appeared reasonable (δ iso 0(50)), the overall line shape (Ω = 880 ppm, κ = −0.3(2)) was not consistent with the near axially symmetric geometry expected for the triodidostannate anion, leading to the conclusion that the anion in this solid cannot be SnI 3 – . A signal, assigned to the SnClI 2 – , was observed in the ESI negative mode mass spectrum of 12′ , and thus, the tetrabutylammonium salt of SnClI 2 – was prepared and its 119 Sn SSNMR WURST-CPMG spectrum recorded (Supporting Information, Figure S11).…”

“…In 11 , complete halogen exchange occurred. The Raman spectrum of 12 (Supporting Information, Figure S1) does not contain signals consistent with the triodidostannate anion (162, 148, 61, 48 cm –1 ). , A broad absorption at 133 cm –1 was observed. In contrast, the ESI-MS negative mode spectrum of 12 reveals a prominent mass cluster centered at m / z 500 that does correspond to SnI 3 – .…”

“…The signal has the expected line shape (Ω = 700 ppm, κ = 0.75) for a system distorted from axial symmetry. The triodidostannate anion was prepared independently as the [NBu 4 ][SnI 3 ] salt . The 119 Sn static WURST-CPMG spectrum of the salt (Supporting Information, Figure S9) resembled the deshielded signal of 12 , although the isotropic shift was considerably less shielded (δ iso 250, Ω = 900 ppm, κ = 0.8).…”