Synthesis and spectroscopic characterization of R₃Sn^IV derivatives of N‐acetyldipeptides

Abstract

Triorganotin(IV) derivatives of N‐acetyldipeptides R3SnAcDip; RMe, Et, n‐Bu, n‐Oct, Cy or Ph (HAcDipN‐acetylglycylglycine and N‐acetylglycylvaline; RMe, n‐Bu, Cy, HAcDipN‐acetylglycylalanine) were obtained by neutralization of R3SnOH and HAcDip. The complexes were studied by means of 119Sn Mössbauer, IR and 1H, 13C and 119Sn NMR spectroscopy. The CSnC bond angles have been inferred by rationalization of Mössbauer nuclear quadrupole splittings as well as from NMR coupling constants. Correlations of Mössbauer isomer shifts with partial atomic charges on tin atoms have been determined: Polymeric trigonal bipyramidal structures, with near‐planar R3Sn units and axial carboxylate (unidentate) and CO amide donor groups are inferred for all the compounds in the solid state, except for Cy3SnAcGlyVal for which a tetrahedral structure is proposed. In solution the complexes are monomeric; in methanol a solvent molecule is coordinated to tin which then is still in a trigonal bipyramidal environment.

Syntheses, characterizations, and crystal structures of organotin(IV) chloride complexes with 4,4′‐bipyridine

“…The tin-proton and tin-carbon coupling constants observed are different from those observed for the starting organotin(IV) derivatives [19], similar to those found in the literature for undissociated trans-octahedral diorganotin(IV) complexes [20]. In the 13 C NMR spectra of the complexes (1)-(6), which are generally consistent with the conclusions drawn from 1 H NMR results, the signals of ligand are shifted only very slightly from their position in the spectrum of free donor ligand. However, the magnitude of J Sn−C and the values of chemical shift of the carbons band to organotin(IV) are different from those reported for starting organotin(IV) derivatives and are similar to those indicated for petra-or hexacoordinate tin(IV) complexes [21].…”

“…They are due to asym and sym Sn C stretching vibrations and are consistent with an essentially trigonal pyramidal arrangement of organic groups [13]. The spectra of (1) is also consistent with an essentially pyramidal arrangement of phenyl groups, the asym and sym Sn C being observed at ca 277 and 229 cm −1 , respectively.…”

“…1 H, 13 C, and 119 Sn NMR spectra were recorded on a Bruker AMX-300 spectrometer operating at 300, 75.3, and 111.9 MHz, respectively. The spectra were acquired at room temperature (298 K) unless otherwise specified; 13 C spectra are broadband proton decoupled. The chemical shifts were reported in ppm with respect to the references and were stated relative to external tetramethylsilane (TMS) for 1 H and 13 C NMR, and to neat tetramethyltin for 119 Sn NMR.…”

“…We have synthesized six organotin(IV) derivatives of 4,4 -bpy and characterized them by elemental analysis, IR, 1 H, 13 C, 119 Sn NMR spectroscopy. Complexes (1), (2), (4), and (6) have also been studied by X-ray crystallography.…”

119mSn Mössbauer studies on tin compounds

“…Lastly, structural assignments by the correlation of the 119Sn M6ssbauer isomer shift parameter, D, with the partial atomic charge on tin, QSn, as described in section 14.7.1, have been effected for a series of assumed fivecoordinated species Alk2Sn 1v -and Alk3SnlV-hemoglobin and -DNA, as well as for series of model systems in the solid state and in solution phases [90,190). The structures thus inferred for the hemoglobin and DNA complexes correspond to those extracted from I'lE rationalizations (Table 14.5 and Figure 14.15).…”