Hydrophenylation of ethylene using a cationic Ru(ii) catalyst: comparison to a neutral Ru(ii) catalyst

Beyond Friedel and Crafts: Innate Alkylation of C−H Bonds in Arenes

“…Based on these results, more efficient catalysts with higher turnovers at lower temperatures have been reported. The electron‐deficient characters of the ligands and metal centers in these complexes noticeably increase the binding affinity of benzene, thereby favoring cleavage of the C−H bond (Scheme ) …”

Oxidative Hydrophenylation of Ethylene Using a Cationic Ru(II) Catalyst: Styrene Production with Ethylene as the Oxidant

“…Cyclic voltammetry of complex 4 shows a reversible Ru(III/II) oxidation at 0.86 V (vs. NHE), which is a +0.04 V shift compared to the previously reported complex, [(HC(pz 5 ) 3 Ru(P(OCH 2 ) 3 )CEt)(NCMe)Ph][BAr′ 4 ] . Chart 1 shows a series of Ru(II) complexes with P(OCH 2 ) 3 CEt, NCMe and Ph ligands coordinated by different tridentate ligands and Ru(III/II) potentials ,,. Surprisingly, the exchange of HC(pz 5 ) 3 with MeOTTM has negligible impact on the Ru(III/II) redox potential.…”

“…The ruthenium precursor (η 6 ‐ p ‐cymene)Ru(P(OCH 2 ) 3 CEt)(Ph)Br ( 1 ) and the proligand MeOTMM {4,4’,4’’‐(methoxymethanetriyl)tris(1‐benzyl‐1H‐1,2,3‐triazole)} were prepared according to literature procedures ,. An acetonitrile solution of complex 1 was heated for 3.5 hours at 70 °C to yield the putative complex (NCMe) 3 Ru[P(OCH 2 ) 3 CEt](Ph)Br ( 2 ) . Complex 2 was then reacted with MeOTTM to produce [(MeOTTM)Ru(P(OCH 2 ) 3 CEt)(NCMe)Ph]Br ( 3 ) in 76 % isolated yield.…”

“…Thus, the cationic Ru(II) complex was synthesized using HC(pz 5 ) 3 (HC(pz 5 ) 3 =tris(5‐methyl‐pyrazolyl)methane) in which the pyrazolyl 5‐positions are protected by incorporation of methyl substituents. Under optimized conditions, the cationic Ru(II) complex [(HC(pz 5 ) 3 )Ru(P(OCH 2 ) 3 CEt)(NCMe)Ph][BAr′ 4 ] successfully increased the TON (turnover numbers) of the ethylene hydrophenylation reaction by over 30‐fold compared to TpRu(P(OCH 2 ) 3 CEt)(NCMe)Ph ,…”

“…Thus, we sought to prepare a Ru(II) catalyst precursor supported by a tris(triazolyl)methanol ligand to test for ethylene hydrophenylation. Since we have obtained data to directly compare catalytic ethylene hydrophenylation using TpRu(P(OCH 2 ) 3 CEt)(NCMe)Ph and [(HC(pz 5 ) 3 )Ru(P(OCH 2 ) 3 CEt)(NCMe)Ph][BAr′ 4 ], we sought to prepare variations of this motif with tris(triazolyl)methanol in place of Tp and HC(pz 5 ) 3 . Herein, we report on the synthesis and studies of catalytic ethylene hydrophenylation, including the surprising result of selective styrene production in which ethylene serves as oxidant (see Ru(II) catalyst on right in Scheme ).…”