Ruthenium(II) Complexes Containing Bis(2-(diphenylphosphino)phenyl) Ether and Their Catalytic Activity in Hydrogenation Reactions

The half-sandwich complexes [(η⁵-C₅H₅)RuCl(DPEphos)] (1) and [{(η⁶-p-cymene)RuCl₂}₂(μ-DPEphos)] (2) were synthesized by the reaction of bis(2-(diphenylphosphino)phenyl) ether (DPEphos) with a mixture of ruthenium trichloride trihydrate and cyclopentadiene and with [(η⁶-p-cymene)RuCl₂]₂, respectively. Treatment of DPEphos with cis-[RuCl₂(dmso)₄] afforded fac-[RuCl₂(κ³-P,O,P-DPEphos)(dmso)] (3). The dmso ligand in 3 can be substituted by pyridine, 2,2‘-bipyridine, 4,4‘-bipyridine, and PPh₃ to yield trans,cis-[RuCl₂(DPEphos)(C₅H₅N)₂] (4), cis,cis-[RuCl₂(DPEphos)(2,2‘-bipyridine)] (5), trans,cis-[RuCl₂(DPEphos)(μ-4,4‘-bipyridine)]_n (6), and mer,trans-[RuCl₂(κ³-P,P,O-DPEphos)(PPh₃)] (7), respectively. Refluxing [(η⁶-p-cymene)RuCl₂]₂ with DPEphos in moist acetonitrile leads to the elimination of the p-cymene group and the formation of the octahedral complex cis,cis-[RuCl₂(DPEphos)(H₂O)(CH₃CN)] (8). The structures of the complexes 1−5, 7, and 8 are confirmed by X-ray crystallography. The catalytic activity of these complexes for the hydrogenation of styrene is studied.