Final Activity Report Summary - CATALMET (Design of catalysts and alkene metathesis)
The project objectives aimed at the preparation of new metal catalysts for selective Catalytic combinations /transformations of molecules in order to contribute to greener aspects of chemistry and sustainable development via energy and atom economy. The main objectives focused on preparation of alkene metathesis catalysts and catalysis and related cross C-C bond formation reactions in order to selectively transform simple molecules and natural products into valuable compounds. The preparation of ruthenium catalysts was planned as the first target.
Cationic nitrogen-heterocyclic carbene (NHC) containing Ru-complexes were prepared and activated to obtain in situ metathesis initiator for ring-closing metathesis. Their activity was in the range of that of phosphine containing complexes.
Two types of polydentate ligands and related ruthenium complexes were prepared. hexakis(benzimidazolyl) ligand was prepared and allowed to bind six Ruthenium atoms. This complex was fully characterised and showed a spherical structure and its catalytic activity was studied in ring-closing metathesis and cross-metathesis reactions.
The synthesis of new dendrimer-like ligands containing six benzimidazolium halide moieties was performed. They can serve as precursors for polycarbenes which were used to make polyruthenium intermediates with potential in alkene metathesis and cross C-C bond formation.
A croos coupling reaction with unsaturated aminoacid derivative and long chain unsaturated ester was performed and needs developments toward surfactants for example. The polyimidazolium and polybenzimidazolium salts as NHC precursors were studied as well for direct C-C bond formation via C-H bond activation. Three important results were obtained:
-The poly NHC-Ru catalysts perform direct C-C bond formation of phenylpyridine and heterocycles,
-The (NHC)RuCl2 based systems are not the most efficient catalysts and the replacement of chlorides by carboxylates largely improves the ruthenium catalyst activity for C-C bond formation.
-Simple ruthenium-carboxylate catalysts favour the direct arylation of heterocycles with arylchlorides with respect to arylbromides.
Similar direct C-C bond formation via C-H bond functionalisation was performed with ligand free palladium-acetate in the direct arylation of heteroaromatics. It was demonstrated that low-loading (less than 0.1 mol %) of Pd(OAc)2 as catalyst precursor can be used in direct arylation via C-H bond activation of thiazoles, thiophenes and furans for a wide range of functions. However in that case the procedure is limited to more reactive electron-poor aryl bromides. Turnover numbers up to 10000 have been obtained for the coupling of activated aryl bromides.
Cationic nitrogen-heterocyclic carbene (NHC) containing Ru-complexes were prepared and activated to obtain in situ metathesis initiator for ring-closing metathesis. Their activity was in the range of that of phosphine containing complexes.
Two types of polydentate ligands and related ruthenium complexes were prepared. hexakis(benzimidazolyl) ligand was prepared and allowed to bind six Ruthenium atoms. This complex was fully characterised and showed a spherical structure and its catalytic activity was studied in ring-closing metathesis and cross-metathesis reactions.
The synthesis of new dendrimer-like ligands containing six benzimidazolium halide moieties was performed. They can serve as precursors for polycarbenes which were used to make polyruthenium intermediates with potential in alkene metathesis and cross C-C bond formation.
A croos coupling reaction with unsaturated aminoacid derivative and long chain unsaturated ester was performed and needs developments toward surfactants for example. The polyimidazolium and polybenzimidazolium salts as NHC precursors were studied as well for direct C-C bond formation via C-H bond activation. Three important results were obtained:
-The poly NHC-Ru catalysts perform direct C-C bond formation of phenylpyridine and heterocycles,
-The (NHC)RuCl2 based systems are not the most efficient catalysts and the replacement of chlorides by carboxylates largely improves the ruthenium catalyst activity for C-C bond formation.
-Simple ruthenium-carboxylate catalysts favour the direct arylation of heterocycles with arylchlorides with respect to arylbromides.
Similar direct C-C bond formation via C-H bond functionalisation was performed with ligand free palladium-acetate in the direct arylation of heteroaromatics. It was demonstrated that low-loading (less than 0.1 mol %) of Pd(OAc)2 as catalyst precursor can be used in direct arylation via C-H bond activation of thiazoles, thiophenes and furans for a wide range of functions. However in that case the procedure is limited to more reactive electron-poor aryl bromides. Turnover numbers up to 10000 have been obtained for the coupling of activated aryl bromides.