Titre :	From homogeneous to heterogeneous catalysis for solvent-free olefin epoxidation using molybdenum pre-catalysts
Type de document :	texte imprimé
Auteurs :	Weili Wang, Auteur ; Rinaldo Poli, Directeur de thèse ; Dominique Agustin, Directeur de thèse
Langues :	Français (fre)
Tags :	HOMOGENEOUS CATALYSIS  HETEROGENEOUS CATALYSIS  EPOXIDATION WITHOUT ORGANIC SOLVENT MOLYBDENUM  GREEN CHEMISTRY  GRAFTING ON SUPPORT  LIMONENE  CYCLOOCTENE
Résumé :	"The work of this PhD thesis deals with the study of molybdenum complexes of general formula [MoO2L]n (L being a tridentate Schiff base ligand with an ONO or ONS coordination sphere around the molybdenum) as catalysts for the organic solvent-free epoxidation of olefins. Within the spirit of Green Chemistry, the work has focused on four of the twelve Green Chemistry principles: the use of catalysis rather than stoichiometric transformations, the use of organic solvent-free procedures rather than operating in solution of organic solvents, the use of renewable substrates and the grafting of catalysts for their recovery. The first part of the manuscript presents a concise state of the art on the chemistry of molybdenum complexes with ligands similar to those used within the thesis. Specific aspects such as the effect of ligand substituents and the different activities – mainly catalytic – observed in organic media are reviewed. A section of this chapter is dedicated to the different strategies employed for the grafting of molybdenum complexes to solid supports as well as to the use of the resulting supported complexes in heterogenized homogeneous catalysis. The next chapter details the synthesis and characterization of all the molecular complexes used as catalysts. This chapter shows the different substitutions operated on the ligands, i.e. changing the ONO coordination sphere to ONS and adding different substituents on the ligands, i.e. OH free functions or additional donor (diethylamino) and/or withdrawing (nitro) substituents at different positions on the tridentate ligand in order to modify the catalytic activity. Six of the synthesized complexes could be characterized by X-ray crystallography. The third chapter reports the results obtained for the catalyzed organic solvent-free epoxidation of cyclooctene as a model substrate using all the molybdenum complexes presented in the previous chapter. It is shown that the nature of the coordination sphere around the molybdenum (ONO vs ONS) is in favour of the latter in terms of catalytic activity towards the formation of the desired epoxide. The catalyzed reactions with complexes containing an OH substituent at different positions on the aromatic ring have shown more significant effects in the case of the ONO coordination sphere than in the corresponding ONS case. The epoxidation performed in the presence of a dimethylamino and/or a nitro substituent on the ONO ligand revealed that the catalytic activity is enhanced by the electron withdrawing group. The catalytic investigations were pursued by the epoxidation of cyclohexene and of one natural substrate, limonene. This study has shown that limonene oxides and/or limonene diols are generated, depending on the nature of the catalyst. The ONS complexes are very reactive and quickly lead to the limonene diols. The effect of different parameters has been studied with particular attention to the reaction temperature. Finally, one stable molybdenum complex with an ONO coordination sphere has been grafted onto a commercial Merrifield resin. Different grafting strategies are presented. The isolated objects have been tested as catalysts under organic solvent-free conditions for the epoxidation of cyclooctene. The catalytic results are promising in terms of activity and the recovery/recycling tests have shown that the catalysts could be used three times without significant decrease of conversion and selectivity, but some metal leaching was observed."
Document :	Thèse de Doctorat
Etablissement_delivrance :	Université Toulouse 3
Date_soutenance :	17/09/2015
Ecole_doctorale :	Sciences de la matière (SdM)
Domaine :	Chimie organométallique de coordination
En ligne :	http://thesesups.ups-tlse.fr/2917/

From homogeneous to heterogeneous catalysis for solvent-free olefin epoxidation using molybdenum pre-catalysts [texte imprimé] / Weili Wang, Auteur ; Rinaldo Poli, Directeur de thèse ; Dominique Agustin, Directeur de thèse . - [s.d.].
Langues : Français (fre)

Tags :	HOMOGENEOUS CATALYSIS  HETEROGENEOUS CATALYSIS  EPOXIDATION WITHOUT ORGANIC SOLVENT MOLYBDENUM  GREEN CHEMISTRY  GRAFTING ON SUPPORT  LIMONENE  CYCLOOCTENE
Résumé :	"The work of this PhD thesis deals with the study of molybdenum complexes of general formula [MoO2L]n (L being a tridentate Schiff base ligand with an ONO or ONS coordination sphere around the molybdenum) as catalysts for the organic solvent-free epoxidation of olefins. Within the spirit of Green Chemistry, the work has focused on four of the twelve Green Chemistry principles: the use of catalysis rather than stoichiometric transformations, the use of organic solvent-free procedures rather than operating in solution of organic solvents, the use of renewable substrates and the grafting of catalysts for their recovery. The first part of the manuscript presents a concise state of the art on the chemistry of molybdenum complexes with ligands similar to those used within the thesis. Specific aspects such as the effect of ligand substituents and the different activities – mainly catalytic – observed in organic media are reviewed. A section of this chapter is dedicated to the different strategies employed for the grafting of molybdenum complexes to solid supports as well as to the use of the resulting supported complexes in heterogenized homogeneous catalysis. The next chapter details the synthesis and characterization of all the molecular complexes used as catalysts. This chapter shows the different substitutions operated on the ligands, i.e. changing the ONO coordination sphere to ONS and adding different substituents on the ligands, i.e. OH free functions or additional donor (diethylamino) and/or withdrawing (nitro) substituents at different positions on the tridentate ligand in order to modify the catalytic activity. Six of the synthesized complexes could be characterized by X-ray crystallography. The third chapter reports the results obtained for the catalyzed organic solvent-free epoxidation of cyclooctene as a model substrate using all the molybdenum complexes presented in the previous chapter. It is shown that the nature of the coordination sphere around the molybdenum (ONO vs ONS) is in favour of the latter in terms of catalytic activity towards the formation of the desired epoxide. The catalyzed reactions with complexes containing an OH substituent at different positions on the aromatic ring have shown more significant effects in the case of the ONO coordination sphere than in the corresponding ONS case. The epoxidation performed in the presence of a dimethylamino and/or a nitro substituent on the ONO ligand revealed that the catalytic activity is enhanced by the electron withdrawing group. The catalytic investigations were pursued by the epoxidation of cyclohexene and of one natural substrate, limonene. This study has shown that limonene oxides and/or limonene diols are generated, depending on the nature of the catalyst. The ONS complexes are very reactive and quickly lead to the limonene diols. The effect of different parameters has been studied with particular attention to the reaction temperature. Finally, one stable molybdenum complex with an ONO coordination sphere has been grafted onto a commercial Merrifield resin. Different grafting strategies are presented. The isolated objects have been tested as catalysts under organic solvent-free conditions for the epoxidation of cyclooctene. The catalytic results are promising in terms of activity and the recovery/recycling tests have shown that the catalysts could be used three times without significant decrease of conversion and selectivity, but some metal leaching was observed."
Document :	Thèse de Doctorat
Etablissement_delivrance :	Université Toulouse 3
Date_soutenance :	17/09/2015
Ecole_doctorale :	Sciences de la matière (SdM)
Domaine :	Chimie organométallique de coordination
En ligne :	http://thesesups.ups-tlse.fr/2917/