CRYSTAL AND MOLECULAR-STRUCTURE OF METHYL(L-TRYPTOPHYL-L-ALANINATO)TIN(IV)-METHANOL(1 1) AND MOSSBAUER-SPECTROSCOPY STUDIES OF LATTICE-DYNAMICS OF DIORGANOTIN(IV) DIPEPTIDE COMPLEXES/

The crystal and molecular structure of dimethyl(L-tryptophyl-L-alanina to)tin(IV) (1/1) has been determined by X-ray crystallography. The tin atom, bonding to two methyl carbons [Sn-C(1) 2.107(6), Sn-C(2) 2.121( 8) Angstrom; C(1)-Sn-C(2) 123.8(3)degrees], terminal amino nitrogen [S n-N-amino 2.272(5) Angstrom], deprotonated peptide nitrogen [Sn-N-pept ide 2.064(5) Angstrom] and terminal carboxylate [Sn-O-carboxylate 2.17 4(5) Angstrom], has a five-coordinated trigonal-bipyramidal environmen t. An extended hydrogen-bond network gives rise to one-dimensional pol ymeric chains. The molecular dynamics of three tryptophan-containing d ipeptide complexes with R(2)Sn(IV) (dipeptide dianion = Trp-AlaO, R = Me or Ph; dipeptide dianion = TrpTyrO, R = Me) have been investigated by variable-temperature Sn-119 Mossbauer spectroscopy. The complexes b ehaved as Debye solids and, in particular, the calculated mean-square displacements of the tin atom confirm the occurrence of monomeric stru ctures in such complexes interconnected through hydrogen bonds, which appear to be much stronger in SnMe(2)(Trp-AlaO) and SnMe(2)(Trp-TyrO) than in SnPh(2)(Trp-AlaO).