Bis{[2,6-diacetylpyridine bis(2-furoylhydrazone)(1–)]dimethyltin(IV)}trans-Tetrachlorodi-methylstannate(IV)

Theoretical and Experimental Study of Tri- and Tetrahalodiorganostannate(IV) Salts. Solvent Dependence in the Reaction of Dimethyltin Dibromide with Tetraethylammonium Bromide

“…Although a highly anisotropic motion was noted for C(1), no evidence was found for split sites. In contrast to the structure of most [SnMe 2 Cl 3 ] - anions, which are associated as dimers, 8c, the structure of 3 contains isolated [SnMe 2 Br 3 ] - anions with the shortest intermolecular Sn···Br distance being 4.240(2) Å. In agreement with the spectroscopic results for 2 , the [SnMe 2 Br 3 ] - anions have a trigonal-bipyramidal structure with the Me groups in equatorial positions.…”

“…The simplest one is vibrational spectroscopy, because the octahedral centrosymmetrical [SnMe 2 Br 4 ] 2- anions (idealized D 4 h symmetry) show only one tin−carbon stretching vibration in the IR and Raman spectra, with mutual exclusion, while the trigonal-bipyramidal [SnMe 2 Br 3 ] - anion (idealized C 2 v symmetry) shows two ν(Sn−C) bands in the IR and Raman spectra, with concordance of activities (see Experimental Section). The above conclusion would not be altered if [SnMe 2 Br 3 ] - anions were associated into dimers as most [SnMe 2 Cl 3 ] - anions are, 8c, because the bent C−Sn−C arrangement would also lead to the appearance of two ν(Sn−C) bands in the IR and Raman spectra.…”

“…The isotropic chemical shifts, −305 ppm for 1 and −135 ppm for 2 , are in the middle of the ranges corresponding to coordination numbers 6 and 5, respectively. It is interesting to note that the isotropic chemical shift for 2 is not close to the limit corresponding to hexacoordinated complexes, so that it could have a structure containing isolated anions, in contrast to the structures observed for [SnMe 2 Cl 3 ] - anions that are generally associated as dimers. 8c, …”

“…For example, we have recently shown that the previously reported [Bu n 4 N] 2 [SnMe 2 I 4 ] is actually a 1:1 mixture of Bu n 4 NI and [Bu n 4 N][SnMe 2 I 3 ], and it is interesting to learn about the factors that influence the crystallization of either type of salt. In the case of [SnR 2 X 4 ] 2- anions, many crystal structures with X = Cl (R = Me, Et, vinyl, Ph) are known, while for the other halides, only the crystal structures of (NH 4 ) 2 [SnMe 2 F 4 ],12a (C 5 H 5 NH) 2 [SnPh 2 Br 4 ],12b and the zwitterionic species [Me 2 (ClCH 2 )N(CH 2 ) 3 ] 2 SnF 4 12c have been reported. In the case of [SnR 2 X 3 ] - anions, only when X = Cl, there are crystal structures available in the literature. 8c,11d,− While the crystal structures reported for [SnPh 2 Cl 3 ] - anions, 11d, one structure containing [SnEt 2 Cl 3 ] - ,14a and one structure containing [SnMe 2 Cl 3 ] - show isolated ions with the organic groups in the equatorial positions of a trigonal-bipyramidal structure, most [SnMe 2 Cl 3 ] - anions are associated into dimers through more or less strong chlorine bridges. 8c, To improve our understanding of the energetic factors affecting the formation of [SnR 2 X 4 ] 2- and [SnR 2 X 3 ] - anions, as well as the bonding and structural features of both kinds of anions, we have performed ab initio SCF MO calculations on the gas-phase structures of SnMe 2 X 2 , [SnMe 2 X 3 ] - , trans -[SnMe 2 X 4 ] 2- (X = F, Cl, Br, I), cis -[SnR 2 Cl 4 ] 2- (R = Me, Et), SnEt 2 Cl 2 , [SnEt 2 Cl 3 ] - , and trans -[SnEt 2 Cl 4 ] 2- .…”

“…In the case of [SnR 2 X 4 ] 2- anions, many crystal structures with X = Cl (R = Me, Et, vinyl, Ph) are known, while for the other halides, only the crystal structures of (NH 4 ) 2 [SnMe 2 F 4 ],12a (C 5 H 5 NH) 2 [SnPh 2 Br 4 ],12b and the zwitterionic species [Me 2 (ClCH 2 )N(CH 2 ) 3 ] 2 SnF 4 12c have been reported. In the case of [SnR 2 X 3 ] - anions, only when X = Cl, there are crystal structures available in the literature. 8c,11d,− While the crystal structures reported for [SnPh 2 Cl 3 ] - anions, 11d, one structure containing [SnEt 2 Cl 3 ] - ,14a and one structure containing [SnMe 2 Cl 3 ] - show isolated ions with the organic groups in the equatorial positions of a trigonal-bipyramidal structure, most [SnMe 2 Cl 3 ] - anions are associated into dimers through more or less strong chlorine bridges. 8c, To improve our understanding of the energetic factors affecting the formation of [SnR 2 X 4 ] 2- and [SnR 2 X 3 ] - anions, as well as the bonding and structural features of both kinds of anions, we have performed ab initio SCF MO calculations on the gas-phase structures of SnMe 2 X 2 , [SnMe 2 X 3 ] - , trans -[SnMe 2 X 4 ] 2- (X = F, Cl, Br, I), cis -[SnR 2 Cl 4 ] 2- (R = Me, Et), SnEt 2 Cl 2 , [SnEt 2 Cl 3 ] - , and trans -[SnEt 2 Cl 4 ] 2- . The calculated gas-phase structures can show small bonding and structural trends that cannot be disclosed by the experimental X-ray crystal structures because of the strong influence of crystal-packing effects on the bond lengths and angles. ,, Given the scarcity of structural data for [SnR 2 Br 4 ] 2- and [SnR 2 Br 3 ] - complexes, we have solved the crystal structure of one complex of each kind and compared the calculated gas-phase structures with the experimental solution and solid-state structures.…”