Reactivity of Ruthenium(II) Complexes Bearing Bis-NHC Ligands

Bis-imidazolium salts bearing N-2- fluorobenzyl substituents and methylene, ethylene, or propylene linkers ([H-2-4]Br-2-[H-2-6]Br-2) and the bis-imidazolium salt [H-2-8]Br-2 featuring an ethylene linker and N-3-fluorophenyl substituents have been prepared. Salts [H-2-5]Br-2 and [H-2-6]Br-2 react with [RuCl2(CO)(2)](n) to give the bis-NHC chelate complexes [9] and [10]. Chloride substitution in [10] for the 2-nitrophenyl isocyanide ligand 11 yielded the complex [12]PF6. The nitro group of the isocyanide in [12]PF6 could not be reduced. Salts [H-2-4]Br-2 and [H-2-5]Br-2 yield with [RuCp*(MeCN)(3)]PF6 the chelate complexes [13]PF6 and [14]PF6, respectively. The propylene-bridged bis-imidazolium salt [H-2-6]Br-2 reacts with [RuCp*(MeCN)(3)]PF6 to give, via an oxidative addition of a C-H bond of the central methylene group of the linker, the seven-coordinate RuIV complex [15]PF6 bearing a tridentate CNHCCalkylCNHC ligand and a hydrido ligand. Introduction of a nitrophenyl isocyanide ligand to [14]PF6 and reduction of the nitro group to the primary amine was also possible. Finally, [H-2-8]Br-2 reacts with [RuCp*(MeCN)(3)]PF6 to give, after intramolecular oxidative addition of a C-aryl-H bond followed by reductive elimination of an imidazolium group, the complex [20]PF6 bearing a unique tridentate CarylCNHCC=C-imidazolium chelate ligand.

Automated summary

Various bis-imidazolium salts were synthesized and their reactions with metal complexes were studied in this research, resulting in the successful preparation of several coordination compounds, with an investigation into the relationship between their structures and properties.