New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine as models for metal-protein interactions:: Synthesis and structural characterization.: Crystal structure of Me2Sn(Tyr-Phe) • MeOH

New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine (H(2)Tyr-Phe) with general formulae R(2)Sn(Tyr-Phe) where R = Me, n-Bu, n-Oct and Ph, and R(3)'Sn(HTyr-Phe) where R' = Me and Ph have been synthesized. The bonding and coordination behaviour in these derivatives are discussed on the basis of FT-IR, multinuclear (1)H, (13)C and (119)Sn NMR and (119)Sn Mossbauer spectroscopic studies. These investigations suggest that dipeptide in R(2)Sn(Tyr-Phe) acts as dianionic tridentate coordinating through -C(O) O, -NH(2) and (-CO)N(peptide) groups while in case of R(3)'Sn(HTyr-Phe) the ligand acts as monoanionic bidentate coordinating through -C(O)O and -NH(2), and the polyhedron around tin in R(2)Sn(Tyr-Phe) and R'(3)Sn(HTyr-Phe) is a distorted trigonal-bipyramidal. It is further confirmed by the single crystal X-ray structure of Me(2)Sn(Tyr-Phe) center dot MeOH which shows two methyl groups and peptide nitrogen (N(peptide)) in the equatorial positions, while the two axial positions are occupied by the carboxylic oxygen (O(carboxyl)) and the amino nitrogen (N(amino)) atom from the same ligand molecule. One methanol molecule is also present in the asymmetric unit. (C) 2008 Elsevier B.V. All rights reserved.