Reactivity and dissociation of organic ions and organometallics compounds by mass spectrometry

Author(s)

Daniela Maria Tomazela

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2004-12-14

Examining board members

Marcos Nogueira Eberlin; Koiti Araki; Paolo Di Mascio; Susanne Rath; Carlos Roque Duarte Correia

• Advisor: Marcos Nogueira Eberlin

Abstract

The first and second parts of this theses are based on experiments carried out on a pentaquadrupole mass spectrometer. In the first part is proposed a revised and more general definition for distonic ions: "distonic ions should be those displaying high degree of actual charge and spin separation". We choose the ionized compound 2-methylene 1,3-dioxolane to be submitted on some ion-molecule reations that have been used as diagnostic for distonic ion. These results experimentally corroborate the distonic ion nature of this ion as predicted by the theoretical calculations. In the second part is shown the intrinsic gas-phase reactivity of cyclic N-acyliminium ions in Mannish-type reactions with the parent enol silane (vinyloxytrimethylsilane). N-acyliminium ions with endocyclic carbonyl groups locked in s-trans forms participate in an interesting tandem N-acyliminium ion reaction. Product ions were isolated by mass-selection, and structurally characterized by triple-stage mass spectrometric experiments. Becke3LYP/6-311G(d,p) calculations corroborate the proposed reaction mechanisms. The third and fourth parts were carried out on a Q-Tof mass spectrometer using electrospray ionization. The third part is on the caracterization of supermolecular porphyrin species obtained by the coordination of [Ru(bipy)2Cl]+ cations to the pyridyl N-atoms of the meta and para series of isomers of meso-(phenylpyridyl) porphyrins by ESI-MS and ESI-MS/MS. All MS and MS/MS data are fully consistent with the proposed structures showing that the Ru-N(pyP) bond is the weakest bond and the most susceptible to dissociation. The fourth chapter is on the identification of a series of neutral chloro dimers, pincer type, and monomeric palladacycles by ESI(+)-MS and ESI(+)-MS/MS. In most of the applications that involves the use of palladacycles dissolved in organic solvents is often assumed that the neutral nature of the halogen dimers or pincer type structures is usually maintained. The investigations of its acetonitrile solution revealed several of their derived ionic species. In the last part variety of [Ru3O(CH3COO)6(py)2(L')] cationic complexes with three mixed ligands rather loosely bonded via the ruthenium atoms to a central, entirely symmetrical tridentaded and spherical Ru3O-cation and with two pyridines as "anchor" reference ligands have been synthesized and transferred intact and efficiently from methanol solutions to the gas phase environment of a mass spectrometer by soft electrospray ionization (ESI). Using these gaseous and isolated (by mass-selection) complexes, the relative strengths of ligand-metal binding of organometallic complexes have been, for the first time, measured. (AU)