Generation of the 15-Electron Rhodium(II) Complex [RhCl(PPh3)3]+by 1-Electron Oxidation of Wilkinson's Catalyst

Barrière, Frédéric; Geiger, William E.

doi:10.1021/om010077b

Cited by 11 publications

(7 citation statements)

References 26 publications

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“…Cyclic voltammetry experiments were conducted in THF solution (Bu 4 NPF 6 electrolyte). As foreshadowed by the electrochemistry of Wilkinson’s complex, these voltammograms exhibit only irreversible couples. The experiments established that 1 resists reduction but is susceptible to oxidation.…”

Section: Resultsmentioning

confidence: 98%

“…The event at −0.15 V is assigned to [1] +/0 by comparison to the [RhCl(PPh 3 ) 3 ] +/0 couple at 0.035 V, which is also irreversible under comparable conditions. 42 The dichloride [4Cl 2 ] + exhibits complementary behavior: it is unchanged over the range −0.5 to +1 V. The key result is that [4Cl 2 ] + is reduced at −0.96 and −1.43 V (Figure 8, left). The reduction generates a new species that oxidizes near −0.15 V (the [1] 0/+ wave, Figure 8, right).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Specifically, 1 is not reduced at potentials <2 V, but the same solution exhibits oxidations at −0.15 and 0.4 V vs Fc +/0 . The event at −0.15 V is assigned to [ 1 ] +/0 by comparison to the [RhCl(PPh 3 ) 3 ] +/0 couple at 0.035 V, which is also irreversible under comparable conditions . The dichloride [ 4 Cl 2 ] + exhibits complementary behavior: it is unchanged over the range −0.5 to +1 V. The key result is that [ 4 Cl 2 ] + is reduced at −0.96 and −1.43 V (Figure , left).…”

Section: Resultsmentioning

confidence: 99%

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Application of Hemilabile Ligands to “At-Metal Switching” Hydrogenation Catalysis

2020

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The paper describes the development of switchable catalysts: i.e., precatalysts that are activated by a reagent and the resulting active catalyst can be shut off with a second reagent. A concept is introduced involving oxidative addition of a rhodium(I) catalyst with trityl chloride and reductive activation of dichlororhodium(III) phosphines with cobaltocene. Part 1 of the paper describes the development of the catalytic platforms, which are 2-diphenylphosphinoanisole (PPh2An) complexes of Rh and Ir. Part 2 describes the proof of concept as applied to the hydrogenation of styrene, including mechanistic investigations. The rhodium catalysts were developed from Rh2Cl2(C2H4)4, which was converted to Rh2Cl2(C2H4)2(κ1-PPh2An)2 and RhCl(κ1-PPh2An)(κ2-PPh2An). This charge-neutral chloride is a precursor to [Rh(κ2-PPh2An)2]BArF 4 and the precatalyst [RhCl2(κ2-PPh2An)2]BArF 4. The iridium catalysts were developed from Ir2Cl2(coe)4, which reacts with PPh2An to give IrClH(κ2-PPh2C6H4OCH2)(κ2-PPh2An). This cyclometalated complex behaves equivalently to IrCl(PPh2An)2. IrClH(κ2-PPh2C6H4OCH2)(κ2-PPh2An) readily reacts with H2 to form IrClH2(κ1-PPh2An)(κ2-PPh2An), which is a viable precursor to the off-state catalyst [IrCl2(κ2-PPh2An)2]BArF 4. In part 2, we demonstrate that the complexes [MCl2(κ2-PPh2An)2]BArF 4 (M = Rh, Ir) are inactive for styrene hydrogenation, in contrast with the other M-PAn compounds. Especially in the case of Rh, the hydrogenation is well controlled by the addition of selected reagents. Details of oxidative addition/reductive activation (OA/RA) are elucidated using cyclic voltammetry and stoichiometric chemical redox experiments.

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Section: Resultsmentioning

confidence: 98%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Application of Hemilabile Ligands to “At-Metal Switching” Hydrogenation Catalysis

2020

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“…The Rh(III) acyl complexes can be expected to be reducible, and once they are reduced to odd-electron species their reactivity would likely be enhanced. Such rate enhancements have been observed for migratory insertion reactions, − but not so far as we are aware for decarbonylation, other than a reductively initiated radical chain decarbonylation of a rhenium formyl complex .…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Thermal and Reductive Decarbonylation of a Rhodium Trifluoroacetyl Diphosphine Complex

2010

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Acyl complexes of rhodium(III) with chelating diphosphine ligands are well known for their stability toward decarbonylation. However, we have found that the corresponding perfluoro complexes do decarbonylate under mild conditions. In this report we address specifically Rh(dppp)-(COCF 3 )I 2 (dppp = 1,3-bis(diphenylphosphino)propane). Another difference between this compound and rhodium acyl complexes containing monodentate phosphines is that it does not undergo reductive elimination of alkyl halide after decarbonylation. Instead, slow CO dissociation from Rh(dppp)(CO)(CF 3 )I 2 occurs to yield Rh(dppp)(CF 3 )I 2 as the final product. Reduction of the trifluoroacetyl complex is a net two-electron process that also involves decarbonylation, but through a quite different mechanism. The products consist of Rh(dppp)(CO)I, CF 3 anion, and iodide. X-ray crystal structures of both Rh(dppp)(COCF 3 )I 2 and Rh(dppp)(CF 3 )I 2 have been obtained and show the expected square-pyramidal geometry with the acyl/alkyl group in the apical position.

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“…9 It was hypothesized that a Rh(I)-catalyzed cyclocarbonylation reaction of allenol acetates affording α-acetoxy cyclopentadienones may be possible due to the mildness of the reaction conditions and the unlikely prospect of the rhodium(I) catalyst participating in a single electron transfer process under these reaction conditions. 10 Moreover, allenol acetates are well-known and are prepared via a formal [3,3]-sigmatropic rearrangement of a propargyl acetates using a variety of transition metal catalysts such as Ag, Au, Cu, Pt, and Rh. 11 Thus, readily available allenol acetates afford an opportunity to directly access α-acetoxy cyclopentadienones, which in turn can be used as precursors to α-hydroxycarbonyl-containing compounds.…”

Section: Introductionmentioning

confidence: 99%

Rh(I)-Catalyzed Cyclocarbonylation of Allenol Esters To Prepare Acetoxy 4-Alkylidenecyclopent-3-en-2-ones

2009

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A Rh(I)-catalyzed cyclocarbonylation reaction of allenol esters has been examined and its synthetic viability established for the conversion of trisubstituted allenes to bicyclo-[4.3.0], and -[5.3.0] skeletons possessing an α-acetoxy cyclopentadienone. Tetrasubstituted allenol acetates gave elimination products, providing examples of a cyclocarbonylation reaction between an alkyne and a latent cumulene or cumulene equivalent. Cleavage of the acetate affords a free hydroxyl group illustrating the utility of this method for accessing α-hydroxy carbonyls from allenol esters.

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Generation of the 15-Electron Rhodium(II) Complex [RhCl(PPh₃)₃]⁺by 1-Electron Oxidation of Wilkinson's Catalyst

Cited by 11 publications

References 26 publications

Application of Hemilabile Ligands to “At-Metal Switching” Hydrogenation Catalysis

Application of Hemilabile Ligands to “At-Metal Switching” Hydrogenation Catalysis

Comparison of the Thermal and Reductive Decarbonylation of a Rhodium Trifluoroacetyl Diphosphine Complex

Rh(I)-Catalyzed Cyclocarbonylation of Allenol Esters To Prepare Acetoxy 4-Alkylidenecyclopent-3-en-2-ones

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