SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATION OF R3SNIV DERIVATIVES OFN-ACETYLDIPEPTIDES

Triorganotin(IV) derivatives of N-acetyldipeptides R3SnAcDip; R = Me, Et, n-Bu, n-Oct, (v or Ph (HAcDip = N-acetylglycylglycine and N-acetyl glycylvaline; R = Me, n-Bu, Cy, HAcDip = N-acetylglycylalanine) were o btained by neutralization of R3SnOH and HAcDip. The complexes were stu died by means of Sn-119 Mossbauer, IR and H-1, C-13 and Sn-119 NMR spe ctroscopy. The C-Sn-C bond angles have been inferred by rationalizatio n of Mossbauer nuclear quadrupole splittings as well as from NMR coupl ing constants. Correlations of Mossbauer isomer shifts with partial at omic charges on tin atoms have been determined. Polymeric trigonal bip yramidal structures, with near-planar R3Sn units and axial carboxylate (unidentate) and C=O amide donor groups are inferred for all the comp ounds in the solid state, except for Cy3SnAcGlyVal for which a tetrahe dral structure is proposed. In solution the complexes are monomeric; i n methanol a solvent molecule is coordinated to tin which then is stil l in a trigonal bipyramidal environment.