Platinum(II)-Catalyzed Ethylene Hydrophenylation: Switching Selectivity between Alkyl- and Vinylbenzene Production

McKeown, Bradley A.; Gonzalez, Hector Emanuel; Friedfeld, Max R.; Brosnahan, Anna M.; Gunnoe, T. Brent; Cundari, Thomas R.; Sabat, Michal

doi:10.1021/om400306w

Cited by 36 publications

(55 citation statements)

References 44 publications

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“…In the structure of 3 , as in most other structures containing dnbpy, the (NO 2 ) groups are approximately co-planar with their partnered pyridine rings. In fact, of the seven total structures of dnbpy itself [ 49 ], or those containing dnbpy [ 50 , 51 , 52 , 53 , 54 , 55 ], only one of these [ 51 ] has an O–N–C–C torsion angle greater than 13°. The observed co-planarity of the NO 2 groups and the pyridine rings suggests that there is likely strong electronic communication between these substituents and the π system of bipyridine.…”

Section: Resultsmentioning

confidence: 99%

Single-Electron Redox Chemistry on the [Cp*Rh] Platform Enabled by a Nitrated Bipyridyl Ligand

Moore¹,

Henke²,

Lionetti³

et al. 2018

Molecules

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[Cp*Rh] complexes (Cp* = pentamethylcyclopentadienyl) are attracting renewed interest in coordination chemistry and catalysis, but these useful compounds often undergo net two-electron redox cycling that precludes observation of individual one-electron reduction events. Here, we show that a [Cp*Rh] complex bearing the 4,4′-dinitro-2,2′-bipyridyl ligand (dnbpy) (3) can access a distinctive manifold of five oxidation states in organic electrolytes, contrasting with prior work that found no accessible reductions in aqueous electrolyte. These states are readily generated from a newly isolated and fully characterized rhodium(III) precursor complex 3, formulated as [Cp*Rh(dnbpy)Cl]PF6. Single-crystal X-ray diffraction (XRD) data, previously unavailable for the dnbpy ligand bound to the [Cp*Rh] platform, confirm the presence of both [η5-Cp*] and [κ2-dnbpy]. Four individual one-electron reductions of 3 are observed, contrasting sharply with the single two-electron reductions of other [Cp*Rh] complexes. Chemical preparation and the study of the singly reduced species with electronic absorption and electron paramagnetic resonance spectroscopies indicate that the first reduction is predominantly centered on the dnbpy ligand. Comparative cyclic voltammetry studies with [NBu4][PF6] and [NBu4][Cl] as supporting electrolytes indicate that the chloride ligand can be lost from 3 by ligand exchange upon reduction. Spectroelectrochemical studies with ultraviolet (UV)-visible detection reveal isosbestic behavior, confirming the clean interconversion of the reduced forms of 3 inferred from the voltammetry with [NBu4][PF6] as supporting electrolyte. Electrochemical reduction in the presence of triethylammonium results in an irreversible response, but does not give rise to catalytic H2 evolution, contrasting with the reactivity patterns observed in [Cp*Rh] complexes bearing bipyridyl ligands with less electron-withdrawing substituents.

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Section: Resultsmentioning

confidence: 99%

Single-Electron Redox Chemistry on the [Cp*Rh] Platform Enabled by a Nitrated Bipyridyl Ligand

Moore¹,

Henke²,

Lionetti³

et al. 2018

Molecules

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“…Previous work has shown these conditions to be optimal for related Pt(II) catalysts. [23][24][25] Under these conditions, catalyst precursors with bisphosphine ligands (complexes 1-6) showed < 0.1 equivalents of ethylbenzene. Styrene was the dominant product for all of the catalyst precursors 1-6.…”

Section: Resultsmentioning

confidence: 98%

“…[13][14][15][16][17][18][19][20][21][22] Our group has been studying Pt(II) complexes of the type [(N~N)Pt(THF)(Ph)][BAr' 4 ] (N~N = bis-chelating dipyridyl ligand, Ar' = 3,5-bis(trifluoromethyl)phenyl), which have been found to be active catalysts for ethylene hydrophenylation to yield ethylbenzene. 4,[23][24][25][26][27][28] In addition to ethylbenzene, the formation of styrene is typically observed when using these Pt(II) complexes as catalysts. For the [(N~N)Pt(THF)(Ph)][BAr' 4 ] catalysts, the formation of styrene is proposed to occur via β-hydride elimination from [(N~N)Pt(CH 2 CH 2 Ph)] + intermediates followed by styrene dissociation.…”

Section: Introductionmentioning

confidence: 99%

“…23,29,30 We found that variation of the 4,4'-substituents of 2,2'-bipyridyl (bpy) ligands in a series of Pt(II) complexes of the type [( x bpy)Pt(L')(Ph)] + ( x bpy = 4,4'-X-2,2'-bipyridyl; L' = THF or NCMe) results in a systematic change in the ratio of ethylbenzene to styrene. 25 As the substituents in the 4,4′-position became more electron withdrawing, styrene formation becomes more competitive with ethylbenzene production.…”

Section: Introductionmentioning

confidence: 99%

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Phosphine and N-heterocyclic carbene ligands on Pt(II) shift selectivity from ethylene hydrophenylation toward benzene vinylation

Brosnahan

Talbot

McKeown

et al. 2015

Journal of Organometallic Chemistry

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“…Initial exchange of coordinated NCMe with ethylene forms [(MeOTTM)Ru(P(OCH 2 ) 3 CEt)( η 2 ‐C 2 H 4 )Ph][BAr′ 4 ]. Then ethylene inserts into the Ru–Ph bond and results in the formation of a phenethyl intermediate . The complex [(MeOTTM)Ru(P(OCH 2 ) 3 CEt)( η 2 ‐styrene)(H)] + can be formed via β‐hydride elimination from [(MeOTTM)Ru(P(OCH 2 ) 3 CEt)(CH 2 CH 2 Ph)] + .…”

Section: Resultsmentioning

confidence: 99%

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

Jia

Gary

et al. 2017

Israel Journal of Chemistry

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The complex [(MeOTTM)Ru(P(OCH2)3CEt)(NCMe)Ph][BAr′4] (MeOTMM=4,4’,4’’‐(methoxymethanetriyl)‐tris(1‐benzyl‐1H‐1,2,3‐triazole), BAr′4=tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate) is used to catalyze the hydrophenylation of ethylene to produce styrene and ethylbenzene. The selectivity of styrene versus ethylbenzene varies as a function of ethylene pressure, and replacing the MeOTTM ligand with tris(1‐phenyl‐1H‐1,2,3‐triazol‐4‐yl)methanol reduces the selectivity toward styrene. For styrene production ethylene serves as the oxidant to produce ethane, as determined by both 1H NMR spectroscopy and GC‐MS. The Ru(III/II) potentials of [(MeOTTM)Ru[P(OCH2)3CEt](NCMe)Ph][BAr′4] (0.86 V) and [(HC(pz5)3)Ru[P(OCH2)3CEt](NCMe)Ph][BAr′4] (0.82 V) (HC(pz5)3=tris(5‐methyl‐pyrazolyl)methane) are nearly identical. Since catalytic conversion of ethylene and benzene by [(HC(pz5)3)Ru[P(OCH2)3CEt](NCMe)Ph][BAr′4] is known to selectively produce ethylbenzene, the formation of styrene using [(MeOTTM)Ru[P(OCH2)3CEt](NCMe)Ph][BAr′4] is attributed to the substituents on the triazole rings of the MeOTTM ligand.

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Platinum(II)-Catalyzed Ethylene Hydrophenylation: Switching Selectivity between Alkyl- and Vinylbenzene Production

Cited by 36 publications

References 44 publications

Single-Electron Redox Chemistry on the [Cp*Rh] Platform Enabled by a Nitrated Bipyridyl Ligand

Single-Electron Redox Chemistry on the [Cp*Rh] Platform Enabled by a Nitrated Bipyridyl Ligand

Phosphine and N-heterocyclic carbene ligands on Pt(II) shift selectivity from ethylene hydrophenylation toward benzene vinylation

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

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