Potassium hexahydroperoxostannate: synthesis and structure
Potassium hexahydroperoxostannate: synthesis and structure. Ippolitov E.G., Tripol'skaya T.A., Prikhodchenko P.V., Pankratov D.A. //Russian Journal of Inorganic Chemistry. 2001. V.46. №6. P.851-857
Polycrystalline potassium hexahydroperoxostannate was prepared by replacement of hydroxo groups in potassium hexahydroxostannate upon its dissolution in hydrogen peroxide. A comparative study of the product and the starting hydroxostannate by powder X-ray diffraction analysis, thermogravimetry, and IR, 2H, 39K, and 119Sn NMR, and Mössbauer spectroscopy was carried out. The peroxo compound K2Sn(OOH)6 crystallizes in the hexagonal system with a = 7.264(7) Å, c = 10.168(4) Å. IR, NMR, and Mössbauer spectroscopy data show that the tin coordination polyhedron in the peroxo compound is an octahedron formed by the coordinated hydroperoxo groups.
Previously, sodium hexahydroperoxostannate was prepared and characterized by powder X-ray diffraction analysis, thermogravimetry, IR, 1H NMR, and Mossbauer spectroscopy, and by thermodynamic and kinetic method. The tin atom in this compound were found to occur in the octahedral environment of hydroperoxo group. It appeared pertinent to confirm the possibility of formation of this type of tin compound by preparing a new hydroperoxo complex. To this end, we performed the first synthesis of potassium hexahydroperoxostannate. Comparative study of potassium hexahydrosstannate (1) and hexahydroperoxosstannate (2) and their deuterated analogue (1a and 2a, respectively) was carried out by powder X-ray diffraction analysis, thermogravimetry, and IR, NMR (2H, 39K and 119Sn), and Mossbauer spectroscopy.
The Mossbauer spectra of 1 (Fig.) at room temperature exhibit only one singlet, which confirm the octahedral environment of the tin atom (δ = -0.03 ± 0.01 mm/s, Γexp = 0.96 ± 0.01 mm/s). In compound 2, resonance absorption moves toward positive isomer shift (δ = 0.19 ± 0.01 mm/s, Γexp = 0.87 ± 0.01 mm/s) with respect to its position in hydroxo complex 1. No quadrupole splitting is observed in the hydroxoperoxo complex at 293 K. These data are consistent with the results of a Mossbauer study of sodium hexahydroperoxostannate at room temperature, in which a positive isomer shift was also observed.
The up field displacement of the isomer shift for the hydroperoxo- substituted tin complex attests to an increase in the electron density on the tin atomic orbitals. Only the hydroperoxo ligands (more precisely, their antibonding orbital) can serve as the electron density donor. Apparently in the case of compound 2, the electron density transfer from the antibonding orbitals of the hydroperoxo groups is more pronounced than in Na2Sn(OOH)6; obviously, this correlates with the higher stability of potassium hydroperoxostannate.
The absence of quadrupole splitting for compound 2 simplie, on the one hand, that the octahedral environment of the central atom is retained and, on the other hand that this environment is uniform, i.e., that the hydroxo ligands have been completely substituted by hydroperoxo ligands. The quadrupole splitting observed in the Mossbauer spectra of potassium hydroxostannate (1) and hydroperoxostannate (2) (δ = 0.07 ± 0.01 mm/s, Δ = 0.59 ± 0.01 mm/s, Γexp = 1.16 ± 0.02 mm/s for 1; and δ = 0.21 ± 0.01 mm/s, Δ = 0.47 ± 0.02 mm/s, Γexp = 1.17 ± 0.02 mm/s for 2) might be related to the presence of both intra- and intermolecular hydrogen bond in the crystal lattice of these compound. These bond in significantly distort the tin coordination polyhedron which is expressed upon heavy cooling.