Activation of carbon-halogen bond with n-heterocyclic carbene catalysts

ABSTRACTPh.D. ThesisACTIVATION OF CARBON-HALOGEN BOND WITH N-HETEROCYCLIC CARBENE CATALYSTSSedat YAŞARİnönü UniversityGraduate School of Natural and Applied SciencesChemistry Departmentxxxi+1902008Supervisor: Prof. Dr. İsmail ÖZDEMİRRecently, N-heterocyclic carbenes (NHC) and transition metal complexes prepared from them have attracted considerable attention in the field of organometallic chemistry. In comparasion, NHC showed better catalytic activity than the corresponding phosphine ligands , not only due to their strong ? -donating and weak ? -accepting abilities but also the easy of controlling steric effects on nitrogen atoms. The complexes formed between NHC ligands and transition metals more stable than the corresponding analogues phosphine complexes because of the role of the bonding ability of M-NHC. This bond could stand high temperatures so that complexes with NHC bonds could be highly active catalyst. Lately, the need of environmental friendly complexes and the upcoming interest to green chemistry raised importance of NHC ligands and NHC derivative transition metal complexes. These type of complexes could be used in C-C coupling reactions, olefin metathesis, hydroformylation, C-H activation and polymerization as a catalyst. Since the monodentate NHC complexes show higher catalytic activity than the corresponding analogs phosphine complexes, we have chosen monodentate carbene precursors, therefore NHC complexes with transition metals have been prepared and tested for C-H bond activation in various reactions as catalysts.This work could be summarized in five chapters.In the first chapter, 1,3-dialkylimidazolinium 1a-1, 1,3-dialkil-1,3,4,5-tetrahidroprimidinium 5a-ı and 1,3-dialkilbenzimidazolium 8a-p NHC precursors were prepared and their structure were elucidated by spectroscopic techniques.In the second chapter, NHC complexes, obtained by the interaction of a monodentate carbene precursors and a base, reacted with [RuCl2(p-cimene)]2 complexes and the corresponding complexes 3a-g and 3??h, if reacted with [RhCl(COD)]2 4a-e complexes were prepared and their structure was investigated with proper techniques.In the third chapter, NHC obtained from monodentate 1,3,4,5-tetrahydropyrimidinium carbene precursors interacted with a proper base were reacted with [RhCl(COD)]2 compound and 7a-b complexes were synthesized and their structures were figured with proper techniques.In the fourth part, NHC obtained from monodentate 1,3,dialkylbenimidazolidinium carbene precursors interacted with a proper base were reacted with [RuCl2(p-cymene)]2 and 9a-g, 9?b complexes were synthesized at the same time complexes 10a-e were obtained with the reaction of Pd(OAc)2 with the same ligands, and all complexes were structurally elucidated by means of spectroscopy.In the last chapter, prepared monodentate azolinium salts, and carbenes formed in the presence of Pd(OAc)2 have been tested in Suzuki-Miyaura and Mizoroki-Heck bond forming reactions and catalytic activities were investigated. Hence, the catalytic activity of the allylic substrates of the carbene complexes with those of azolinium salts in nucleophilic substitution reactions were given.Keywords: N-Heterocyclic carbene, monodentate carbene precursors, carbenes, C-C bond formation, allylic substitution, monodentate ruthenium, rhodium and palladium carbene complexes.