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)] (<b>A</b>). The addition of a strong base (KO^tBu 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>B</b>). The same borane-bridged compound was obtained when complex <b>A</b> 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