Homo- and hetero-metallic carbonyl clusters based on group 8 transition metals

This PhD thesis presents an investigation of the synthesis, characterization and catalytic properties of homo- and hetero-metallic carbonyl clusters based on Group 8 metals (Fe, Ru, Os). Comprehensive characterization of the synthesized new compounds were achieved through single crystal X-ray diffraction (SC-XRD), FT-IR, multi-nuclear NMR and ESI-MS spectroscopies. The experimental results were also complemented by computational investigations employing DFT studies. The first part of this Thesis focuses on the reactions involving the homo-metallic precursor [HRu3(CO)11]– (1) and complexes of other transition metals (Ir, Cu, Ag, Au), leading to a range of novel hetero-metallic clusters. These Ru-M clusters were tested as catalyst precursors in the transfer hydrogenation reaction of 4-fluoroacetophenone, and compound [H2Ru3Ir(CO)12]– (2) proved also to be active in the hydrogenation of trans-cynnamaldehyde. The reaction between [HRu4(CO)12]3– (12) and Au(PPh3)Cl, under different experimental conditions, yielded new peraurated Ru hydride carbonyl clusters; detailed spectroscopic and computational analyses confirmed their structures, including the identification of weak aurophilic interactions. Furthermore, the redox chemistry of the iron carbide car-bonyl cluster [Fe6C(CO)15]4– (23) was examined. Its chemical oxidation processes were investigated using various oxidants and trapping agents; moreover, electrochemical, IR spectro-electrochemical and DFT studies on 23 have been conducted, in order to unravel the experimental conditions for the functionalization of the Fe6C cage without fragmentation. The SC-XRD molecular structures of novel tri-anionic species of the type [Fe6C(CO)14(SR)]3– are reported. The chirality of the two enantiomers of [Fe6C(CO)14(Cys)]3– (33), derived from reactions with enantiopure L- and D-Cysteine, was assessed through vibrational circular dichroism (VCD) studies, supported by computational simulations. The synthesis and characterization of novel chiral Os3Rh clusters with chiral diphosphine ligands of Walphos family are reported.