Complexes of diorganotin(IV) with aminoacids and a dipeptide. Synthesis and structural investigations.

Abstract

The aim of this work is to synthesize complexes of Arginine, effector of recognition, with organotin(IV) ions (R2Sn2+, R =Me, nBu) which are known to possess antitumour, antimicrobial, anti-inflammatory activities. The complexes were investigated by FT-IR and 119Sn Můssbauer.While identical stoichiometries are present for Me2Sn(Arg)2 and Me2Sn(Boc-Arg)2 complexes, 119Sn Můssbauer spectra give a clear evidence of different coordination modes. L-Arginine appears to behave as a chelating ligand through carboxylate and a-NH2 groups in the former, while in Nα-Boc-L-Arginine complex, the Nα-protected amino group being exempted from coordination, only the carboxylate groups are effectors of bonding to the organometallic moieties. The L-Ala-L-Arg dipeptide complex appears to adopt a trigonal-bipyramidal geometry at tin, the organometallic moiety being coordinated by α-amino, deprotonated peptide nitrogen and terminal carboxylate groups. FT-IR spectra give a clear indication that guanidino groups in all the complexes are not involved in coordination, since ν(C=N-H) frequency of the terminal guanidino group is fairly constant and unshifted relative to the free ligand.