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Synthesis and spectroscopic characterization of dimethyl‐, di‐n‐butyl‐, di‐t‐butyl‐and diphenyl‐tin(iv) derivatives of dipeptides: Crystal and molecular structure of di‐n‐butyltin(iv) glycylvalinate
Author(s) -
MundusGlowacki Brigitte,
Huber Friedo,
Preut Hans,
Ruisi Giuseppe,
Barbieri Renato
Publication year - 1992
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.590060111
Subject(s) - chemistry , denticity , crystal structure , glycylglycine , tin , crystallography , carboxylate , stereochemistry , trigonal bipyramidal molecular geometry , x ray crystallography , diffraction , glycine , biochemistry , organic chemistry , amino acid , physics , optics
The dipeptide complexes R 2 SnL listed below have been synthesized: (a) Me 2 SnL; H 2 L = glycylalanine (H 2 GlyAla), glycylvaline (H 2 GlyVal), glycylmethionine (H 2 GlyMet), glycyltryptophan (H 2 GlyTrp), glycyltyrosine (H 2 GlyTyr); (b) nBu 2 SnL; H 2 L = H 2 GlyAla, H 2 GlyVal; (c) nBu 2 SnL.H 2 O; H 2 L = glycylglycine (H 2 GlyGly), H 2 GlyAla; (d) tBu 2 SnL; H 2 L = H 2 GlyAla, H 2 GlyVal; (e) tBu 2 SnGlyGly. H 2 O; (f) Ph 2 SnL; H 2 L = H 2 GlyAla, H 2 GlyVal, H 2 GlyTyr, H 2 GlyTrp; (g) Ph 2 Sn(HGlyVal) 2 . The crystal and molecular structures of nBu 2 SnGl Val have been determined by single‐crystal X‐ray diffraction. The polyhedron around tin is a distorted trigonal bipyramid, analogous to that of Et 2 SnGlyTyr (see Vornefeld et al. , Appl. Organomet. Chem., 1992, 6: 75). According to infrared and 119 Sn (Δ E parameters) Mössbauer spectroscopic data the R 2 SnL derivatives can be classified by their solid‐state structure into two types which are distinguished by the nature of the axial carboxylate [(i) monodentate, as in nBu 2 SnGlyVal; (ii) bidentate]. Bonding in R 2 SnL.H 2 O and Ph 2 Sn(HGlyVal) 2 has been discussed on the basis of vibrational data. Rationalization of the 119 Sn Mössbauer parameters has been attempted by ‘literal’ point‐charge model, calculations of Δ E in the structural context described above. According to 13 C NMR spectra, compounds Me 2 SnL are undissociated in methanol solutions, whilst dissociation is inferred for aqueous solutions, probably concerning the carboxyl and amino groups only. Five‐coordination in methanol and aqueous solutions has been assumed for Me 2 Snl from 119 Sn NMR chemical shifts. Values of coupling constants | 2 J ( 119 Sn, 1 H)|, determined from 1 H NMR spectra, gave estimates of CSnC angles in Me 2 SnL in the range 128–136° in methanol and aqueous solutions, which correspond to values from 119 Sn Mössbauer Δ E parameters (129.6–133.8°). The structural relationship of R 2 SnL molecules in the solid state and in solution phase has been discussed.