Novel Ruthenium Complexes for Bifunctional Catalysis: the Dual Role of Cyclopentadienone and N-Heterocyclic Carbene

Cesari, Cristiana (2016) Novel Ruthenium Complexes for Bifunctional Catalysis: the Dual Role of Cyclopentadienone and N-Heterocyclic Carbene, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Chimica, 28 Ciclo. DOI 10.6092/unibo/amsdottorato/7525.
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The PhD thesis herein presented deal with the synthesis, characterization and catalytic application of new ruthenium transition metal complexes which exhibit unprecedented combination of ligands: cyclopentadienones and N-heterocyclic carbenes (NHC). In the first year of the PhD work it was developed a straightforward and efficient synthetic route to novel Ru N-heterocyclic carbenes (NHC) complexes by transmetallation of non-bulky imidazolylidene silver complexes to ruthenium dicarbonyl tetraarylcyclopentadienone. The same procedure with sterically demanding NHC resulted in the formation of unprecedented heterobimetallic Ru-Ag(NHC) complexes. During the second year six months (from March to September 2014) have been spent at the UCD School of Chemistry and Chemical Biology, University College of Dublin, under the supervision of Professor Martin Albrecht investigating the steric and electronic tunability of the catalyst precursors by replacing imidazolylidenes with triazolylidenes. Triazolylidenes are stronger donors than imidazolylidenes, and hence they further activate the ruthenium(0) oxidation state in dicarbonyl tetraarylcyclopentadienone Ru (NHC) complexes, which resulted to be beneficial in catalytic applications. During the second and third year the novel classes of ruthenium complexes were successfully employed as catalyst precursors in the transfer hydrogenation of ketones and aldehydes using iPrOH as hydrogen source. Fine tuning of several molecular parameters and reaction conditions allowed to improve catalytic performances. Furthermore, the catalysts were employed for the oxidation of alcohol with promising results. Heterogenization of the catalyst on polypropylene imine dendrimers has been also developed, moreover ionic ruthenium complexes have been also exploited as potential catalyst in ionic liquids. Greener synthetic conditions have been found both for the synthesis of ruthenium complexes under microwave irradiation and for the acid catalysed transformation of the bio-based bis-hydroxymethylfuran. Preliminary electrochemical measurements have been carried out on a triazolylidene Ru(0) complex. Its redox behaviour could be exploited in the development of electrocatalysis.

Tipologia del documento
Tesi di dottorato
Cesari, Cristiana
Dottorato di ricerca
Scuola di dottorato
Scienze chimiche
Settore disciplinare
Settore concorsuale
Parole chiave
N-heterocyclic carbene cyclopentadienone ruthenium iron complexes homogeneous catalysis transfer hydrogenation alcohol oxidation dendrimers ionic liquids microwave irradiation
Data di discussione
10 Maggio 2016

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