Synthesis, Structure Characterization And Catalytic Activity Evaluation Of Organophosphine-based Palladium(?) Complex As A Catalyst For Coupling Reaction

The coupling reactions catalyzed by transition metal compounds are an important means to construct new organic structures and new frameworks?C-C,C-N,C-O,etch?.Among these compounds,palladium-based complexes display best catalytic performance,owing to its unique d-electron configuration.In particular,organic phosphorus-palladium???have been found to be most useful in the synthesis of organic optoelectronic materials,drugs and natural products,for the catalytic activity and selectivity of the complexes can be improved by introducting large and electron-rich organic groups to phosphorus atoms.Based on previous work,six palladium???complexes of phosphorus ligand with large and electron-rich organic groups have been synthesized,structurally characterized and evaluated for the catalytic performance in this thesis,with an aim to meet the market demand for coupling catalysts in China.The work in the thesis mainly includes the following four parts:1.By using commercially available palladium dichloride and palladium dibromide as the starting materials,six palladium???complexes of tert-butylphenylphosphine?t-Bu?₂PPh),di-tert-butyl-?4-dimethylaminophenyl?phosphine?Xantphos?and 4,5-bisdiphenylphosphine-9,9-dimethylxanthene?Amphos?were prepared via the ligand substitution reactions,with a batch of 50-250 g and a purity of more than 98%.The yield was calculated to be 98%both for Pd[?t-Bu?₂PPh]₂X₂?X=Cl,Br?,92.5%?X=Cl?and 85.4%?X=Br?for Pd?Xantphos?X₂,90.8%?X=Cl?and 88.5%?X=Br?for Pd?Amphos?₂X₂.2.The chemical structures of all six palladium???complexes were determined by means of elemental analysis,MS,IR and NMR.Furthermore,single crystals of five complexes were successfully cultured with the conventional solvent volatilization method,and their stereochemical structures were obtained by X-ray single-crystal diffraction analysis?XRD?.3.The catalytic activity of six palladium???complexes was evaluated along with Pd?PPh₃?₄ for comparison,in three typical coupling reactions between halogenated aromatic hydrocarbon and aniline.In the Suzuki coupling reaction of 2-bromothiophene with hydroxyphenylboronic acid,the catalytic conversion rate of Pd[(?t-Bu?₂PPh]₂Br₂,Pd[?t-Bu?₂PPh]₂Cl₂ and Pd?Xantphos?Br₂ was found to be 81%,72%and 69%,respectively,higher than 60%of Pd?PPh₃?₄.In he unilateral Suzuki coupling reaction of4,7-dibromobenzothiadiazole to Penacol Hydroxyphenyl Borate,the catalytic conversion rate of Pd?Amphos?₂Br₂,Pd?Xantphos?Cl₂ and Pd?Xantphos?Br₂ was 83%,76%and 65%,respectively,also greater than that of Pd?PPh₃?₄.Whereas Pd?Xantphos?Br₂ and Pd[?t-u?₂PPh]₂Br₂ showed better catalytic activity with a yield of 62%and 55%,ompared to40%of Pd?PPh₃?₄,in the unilateral Sonogashira coupling reaction of 4,7-dibromobenzothiadiazole and methylbutynol.4.In recent years,platinum-based coupling catalysts have attracted much attention due to the soaring price of palladium in the international market,although the catalytic activity of platinum complexes are known to be lower than the corresponding palladium in many coupling reactions.To explore the substitutability of palladium with platinum,two new platinum complexes Pt[?t-Bu?₂PPh]₂Cl₂and Pt[?t-Bu?₂PPh]₂Br₂ were successfully synthesized and structurally characterized by MS,NMR and X-ray single-crystal diffraction analysis.The evaluation of their catalytic activity in some coupling reactions is under way.