Borane-Bridged Ruthenium Complex Bearing a PNP Ligand: Synthesis and Structural Characterization

Reaction of the precursor complex [RuHCl(CO)(PPh3)(3)] with the PNP protioligand CbzdiphosH in toluene resulted in the formation of two stereoisomeric hydrido complexes, [(CbzdiphosH)RuHCl(CO)] (A). The addition of a strong base ((KOBu)-Bu-t or LiEt3BH), on the other hand, led to the formation of the 1,2-dehydrochlorination product [(Cbzdiphos)RuH(CO)]. The reaction of the latter with BH3.THF at room temperature led to the 1,2-addition of the BH3 moiety to the Ru-N function, forming a RuNBH cycle in [(CbzdiphosHBH(2))RuH(CO)] (B). The same borane-bridged compound was obtained when complex A was treated with NaBH4 in THF. The BH2 group forms a bridging unit between the carbazole-N atom and one of the ruthenium-bound hydrides.