The Catalytic Properties Of Ru-η～6-C₆H₆-diphosphine Complexes For Hydrogenation Of Benzene

According to the reported method, six Ru-η⁶-C₆H₆-diphosphine complexes, [RuCl(η⁶-C₆H₆)(BISBI)]Cl (1) (BISBI = 2,2'-bis(diphenylphosphinomethyl)-1,1'-biphenyl), [RuCl(η⁶-C₆H₆)(BDPX)]Cl (2) (BDPX = 1,2-bis (diphenylphosphinomethyl)benzene), Ru₂Cl₄(η⁶-C₆H₆)₂(μ₂-BDNA) (3) (BDNA = 1,8-bis(diphenylphosphinomethyl)naphthalene), [RuCl(η⁶-C₆H₆)(BISBI)]BF₄ (4), [RuCl(η⁶-C₆H₆)(BDPX)]BF₄ (5) and [(η⁶-C₆H₆)₂Ru₂Cl₂(μ₂-Cl)(μ₂-BDNA)]BF₄ (6) were prepared and used as catalysts for the hydrogenation of benzene both in benzene solution and an aqueous/organic biphase. Their catalytic activities were obviously relative with the compositions or structures of these complexes.In benzene, complexes 1, 2 and 3 were homogeneous catalysts for the hydrogenations of benzene in the conditions of reaction temperature of 100°C and hydrogen pressure of 50atm, complexes 4, 5 and 6 were simultaneously homogeneous and heterogeneous in the same reaction conditions. Among these complexes, 4, 5 and 6 were of higher catalytic activities than 1, 2 and 3. The dinuclear complex 6 in which one chlorine anion was substituted by one tetrafluoroborate gave the highest activity. The higher activities of complex 4, 5 and 6 could be owing to the easy generation of catalytic active species and the formations of Ru(0) particles which were of the highly catalytic activity.In an aqueous/organic biphase, the influence of pH on these...