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RESEARCH PRODUCT

Hypervalent tin-organic compounds: Vibrational spectroscopy in the solid as a tool for structure determination

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Abstract A full set of IR- and Raman spectra down from 600 cm1 has been determined and assigned for 60 penta- or hexacoordinated tin-compounds in the groups RSn(CH2CH2CH2)3N (R = Cl, Br, I, Me), RR'Sn(MCH2CH2)2X (R,R′ = Cl, Br, I, Me, Ph, M = CH2 S; X = NMe, O, S), RPh2SnCH2CH2CH2NMe2 (R = Cl, Br, I) and RMe2Sn—CHD—COOMe (R = F, Cl, Br, I, Me). In these hypervalent compounds an approach of the donor atom X to the central atom tin outlines a ‘path’ of nucleophilic attack from a tetrahedron to a trigonal bipyramid. Along this ‘reaction path’ the bond lengths of the axial ligand increase continuously while the bond lengths of the equatorial ligands slightly decrease. The number of similar hypervalent structures discussed in this paper enabled us to investigate the change of stretching vibrations in a wide range of bond lengths in different atom pairs. Force constants were calculated from the data concerning the stretching vibrations at tin and plotted versus the according distances obtained from X-ray structure analysis. The resulting behavior is discussed with the help of Morse potentials.