title: Gas-phase interactions of organotin compounds with glycine.
abstract: Gas-phase interactions of organotins with glycine have been studied by combining mass spectrometry experiments and quantum calculations. Positive-ion electrospray spectra show that the interaction of di- and tri-organotins with glycine results in the formation of [(R)2Sn(Gly)-H](+) and [(R)3Sn(Gly)](+) ions, respectively. Di-organotin complexes appear much more reactive than those involving tri-organotins. (MS/MS) spectra of the [(R)3Sn(Gly)](+) ions are indeed simple and only show elimination of intact glycine, generating the [(R)3Sn](+) carbocation. On the other hand, MS/MS spectra of [(R)2Sn(Gly)-H](+) complexes are characterized by numerous fragmentation processes. Six of them, associated with elimination of H2O, CO, H2O + CO and formation of [(R)2SnOH](+) (-57 u),[(R)2SnNH2](+) (-58 u) and [(R)2SnH](+) (-73 u), are systematically observed. Use of labeled glycines notably concludes that the hydrogen atoms eliminated in water and H2O + CO are labile hydrogens. A similar conclusion can be made for hydrogens of [(R2)SnOH](+) and [(R2)SnNH2](+) ions. Interestingly, formation [(R)2SnH](+) ions is characterized by a migration of one the α hydrogen of glycine onto the metallic center. Finally, several dissociation routes are observed and are characteristic of a given organic substituent. Calculations indicated that the interaction between organotins and glycine is mostly electrostatic. For [(R)2Sn(Gly)-H](+) complexes, a preferable bidentate interaction of the type η(2)-O,NH2 is observed, similar to that encountered for other metal ions. [(R)3Sn](+) ions strongly stabilize the zwitterionic form of glycine, which is practically degenerate with respect to neutral glycine. In addition, the interconversion between both forms is almost barrierless. Suitable mechanisms are proposed in order to account for the most relevant fragmentation processes.
authors.affiliation: Laboratoire de Chimie-Analytique et Electrochimie, Département de Chimie, Faculté des Sciences de Tunis, Campus Universitaire, 2092, El Manar, Tunis, Tunisia. latrous_latifa@yahoo.fr
authors.forename: Latifa
authors.initials: L
authors.lastname: Latrous
authors.forename: Jeanine
authors.initials: J
authors.lastname: Tortajada
authors.forename: Violette
authors.initials: V
authors.lastname: Haldys
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Léon
authors.forename: Catarina
authors.initials: C
authors.lastname: Correia
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Salpin
mesh_terms: D005740:Gases / Q000737:chemistry; D005998:Glycine / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D009947:Organotin Compounds / Q000737:chemistry*; D011522:Protons; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D005740:Gases; D007477:Ions; D009947:Organotin Compounds; D011522:Protons; D005998:Glycine
keywords: ab initio calculations; gas-phase reaction; glycine; mass spectrometry; organotins