New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine as models for metal–protein interactions: Synthesis and structural characterization. Crystal structure of Me 2Sn(Tyr-Phe) · MeOH

Abstract

New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine (H 2Tyr-Phe) with general formulae R 2Sn(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 1H, 13C and 119Sn NMR and 119Sn Mössbauer spectroscopic studies. These investigations suggest that dipeptide in R 2Sn(Tyr-Phe) acts as dianionic tridentate coordinating through −C(O)O −, –NH 2 and (–CO)N − peptide groups while in case of R ′ 3Sn(HTyr-Phe) the ligand acts as monoanionic bidentate coordinating through –C(O)O − and –NH 2, and the polyhedron around tin in R 2Sn(Tyr-Phe) and R ′ 3Sn(HTyr-Phe) is a distorted trigonal-bipyramidal. It is further confirmed by the single crystal X-ray structure of Me 2Sn(Tyr-Phe) · 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.