Single and double metallic layer-containing ruthenium dendrimers. Synthesis and catalytic properties

The reaction of a series of phosphanyl-terminated carbosilane dendrimers displaying only one phosphorus ligand per arm with [RuCl2(p-cymene)](2) resulted in the grafting of RuCl(p-cymene) moieties on the periphery of the dendrimer. In these species, the chloride ligand is easily displaced by the organic bases pyridine, 4-cyanopyridine and 4,4'-bipyridine to afford new cationic metallodendrimers. NMR studies have confirmed the chirality of the ruthenium centre. The species containing 4,4'-bipyridine reacts through the uncoordinated pyridyl nitrogen with a new equivalent of [RuCl2(p-cymene)](2) or [RhCl(CO)(2)](2) to lead to homo- or hetero-bimetallic layer-containing dendrimeric systems. The ruthenodendrimers were tested as catalysts in the transfer hydrogenation of cyclohexanone by propan-2-ol and their activity compared with that of some analogous mononuclear ruthenium(II) complexes.