Multimetallic compounds and nanoparticles functionalised with transitional metal units for application in catalysis

The introduction (Chapter 1) provides an overview of the main topics encountered in the thesis including the stepwise generation of multimetallic assemblies based on different chelating ligands; gold nanoparticles and surface functionalization; palladium-based catalysts (homogeneous and heterogeneous). This last part focuses on C-H functionalization and Suzuki-Miyaura reactions, reporting examples and dealing with the recovery process and re-use of palladium from secondary sources. Chapter 2 outlines the stepwise generation of mono-, bi- and multimetallic assemblies based on different polyfunctional ligands including dicarboxylates, pyridine derivatives and dithiocarbamates. The synthesis and characterisation of the novel complexes are described along with the immobilisation of a ruthenium compound bearing a disulfide ligand on the surface of gold and palladium nanoparticles. In the third Chapter, the research focus shifts to the synthesis and characterisation of mono- and bi-metallic novel palladium complexes bearing dithiocarbamate ligands. In addition, the preparation of palladium dithiooxamide complexes derived from secondary sources (spent catalytic converters) is described. All the palladium complexes were screened as potential homogeneous catalysts in the C-H activation of benzo[h]quinoline and 8-methylquinoline. The optimisation of the reaction conditions by varying three different factors: catalyst loading, temperature and time; is tested and discussed. In Chapter 4, the use of simple and commercially available iodine and a tetrabutylammonium salt as leaching agents in a palladium recovery process is described. The reactivity of bimetallic palladium complexes generated from the process was then investigated in the C-H activation and Suzuki-Miyaura cross-coupling reactions. Furthermore, a novel route to produce a variety Pd(II) catalyst via ligand exchange reaction of bimetallic palladium complex with inexpensive phosphine ligands is also presented. These catalysts were tested using electron- donating and withdrawing substrates in the cross-coupling reaction of phenylboronic acid. Chapter 5 extends the scope of the research to heterogeneous catalysis. The preparation, characterisation and immobilisation of novel palladium(II) dithiocarbamate complexes are described, along with construction of silica and silica-coated iron-oxide nanoparticles and the support of the complex on the nanoparticles. The reactivity of unsupported and supported complexes toward C-H functionalization of benzo[h]quinoline is discussed. The overall conclusions of the thesis are discussed in Chapter 6. Experimental procedures related to the synthesis, characterisation and catalytic studies of the compounds in Chapter 2 to 5 are detailed in Chapter 7.Open Acces