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 (KOtBu 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 [(CbzdiphosHBH2)­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.