HYPERVALENT TIN-ORGANIC COMPOUNDS - VIBRATIONAL SPECTROSCOPY IN THE SOLID AS A TOOL FOR STRUCTURE DETERMINATION

A full set of IR- and Raman spectra down from 600 cm(-1) has been dete rmined and assigned for 60 penta- or hexacoordinated tin-compounds in the groups RSn(CH2CH2CH2)(3)N (R = Cl, Pr, I, Me), RR'Sn(MCH2CH2)(2)X (R,R' = Cl, Br, I, Me, Ph; M = CH2, S; X = NMe, O, S), RPh2SnCH2CH2CH2 NMe2 (R = Cl, Br, I) and RMe2Sn-CHD-COOMe (R = F, Cl, Br, I, Me). In t hese hypervalent compounds an approach of the donor atom X to the cent ral atom tin outlines a 'path' of nucleophilic attack from a tetrahedr on to a trigonal bipyramid. Along this 'reaction path' the bond length s of the axial ligand increase continuously while the bond lengths of the equatorial ligands slightly decrease. The number of similar hyperv alent structures discussed in this paper enabled us to investigate the change of stretching vibrations in a wide range of bond lengths in di fferent atom pairs. Force constants were calculated from the data conc erning the stretching vibrations at tin and plotted versus the accordi ng distances obtained from X-ray structure analysis. The resulting beh avior is discussed with the help of Morse potentials. (C) 1997 Elsevie r Science B.V.