A Rhodium Peroxido Complex in Mono‐, Di‐, and Peroxygenation Reactions

Meier, Gregor; Braun, Thomas

doi:10.1002/anie.201007315

Cited by 37 publications

(26 citation statements)

References 120 publications

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“…In the 19 F NMR spectrum the tetrafluoropyridyl ligand gives rise to three multiplet signals at δ = –99.8, –107.0, and –116.6 ppm in a 2:1:1 ratio, whereas the signal at δ = –99.8 ppm consists of two overlying multiplets. This indicates a hindered rotation of the tetrafluoropyridyl ligand about the Ir–C bond 3a,9,12. The formation of an iridium(III) complex is supported by an IR spectrum that shows an absorption band at $\tilde {\nu}$ = 2124 cm –1 for the CN t Bu ligand 13.…”

Section: Resultssupporting

confidence: 61%

Synthesis of an Iridium Peroxido Complex and Its Reactivity Towards Brønsted Acids

Baumgarth

Braun

et al. 2015

Eur J Inorg Chem

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Treatment of the iridium(I) complex trans‐[Ir(4‐C5F4N)(CNtBu)(PiPr3)2] (2) with O2 or H2O2 gave the iridium(III) peroxido complex trans‐[Ir(4‐C5F4N)(O2)(CNtBu)(PiPr3)2] (3a). The peroxido complex 3a reacts with Brønsted acids to give the iridium(III) complexes cis‐[Ir(4‐C5F4N)(X)2(CNtBu)(L)(PiPr3)] (4: X = Cl, L = PiPr3, 5: X = CF3COO, L = H2O) and hydrogen peroxide. In the presence of formic acid, 3a yields the carbonato complex trans‐[Ir{κ2‐OC(O)O}(4‐C5F4N)(CNtBu)(PiPr3)2] (6) as the main product. Reactions between formic acid or dihydrogen and the iridium(I) complex 2 give the isomeric dihydrido complexes trans,trans‐[Ir(4‐C5F4N)(H)2(CNtBu)(PiPr3)2] (7a) and cis,trans‐[Ir(4‐C5F4N)(H)2(CNtBu)(PiPr3)2] (9a), respectively.

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Section: Resultssupporting

confidence: 61%

Synthesis of an Iridium Peroxido Complex and Its Reactivity Towards Brønsted Acids

Baumgarth

Braun

et al. 2015

Eur J Inorg Chem

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“…The crystallographic data and spectral features of 4 are consistent with those of related Rh III (η 2 -O 2 ) complexes. 5,34,39,40 The X-ray crystal structure of 4b, which is provided in Figure 3 Inorg. Chem.…”

Section: ■ Resultsmentioning

confidence: 99%

Oxygen Reduction Mechanism of Monometallic Rhodium Hydride Complexes

2015

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The reduction of O2 to H2O mediated by a series of electronically varied rhodium hydride complexes of the form cis,trans-Rh(III)Cl2H(CNAd)(P(4-X-C6H4)3)2 (2) (CNAd = 1-adamantylisocyanide; X = F (2a), Cl (2b), Me (2c), OMe (2d)) was examined through synthetic and kinetic studies. Rhodium(III) hydride 2 reacts with O2 to afford H2O with concomitant generation of trans-Rh(III)Cl3(CNAd)(P(4-X-C6H4)3)2 (3). Kinetic studies of the reaction of the hydride complex 2 with O2 in the presence of HCl revealed a two-term rate law consistent with an HX reductive elimination (HXRE) mechanism, where O2 binds to a rhodium(I) metal center and generates an η(2)-peroxo complex intermediate, trans-Rh(III)Cl(CNAd)(η(2)-O2)(P(4-X-C6H4)3)2 (4), and a hydrogen-atom abstraction (HAA) mechanism, which entails the direct reaction of O2 with the hydride. Experimental data reveal that the rate of reduction of O2 to H2O is enhanced by electron-withdrawing phosphine ligands. Complex 4 was independently prepared by the addition of O2 to trans-Rh(I)Cl(CNAd)(P(4-X-C6H4)3)2 (1). The reactivity of 4 toward HCl reveals that such peroxo complexes are plausible intermediates in the reduction of O2 to H2O. These results show that the given series of electronically varied rhodium(III) hydride complexes facilitate the reduction of O2 to H2O according to a two-term rate law comprising HXRE and HAA pathways and that the relative rates of these two pathways, which can occur simultaneously and competitively, can be systematically modulated by variation of the electronic properties of the ancillary ligand set.

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“…The peroxynation reaction was thought to be a model reaction for direct transfer of a dioxygen unit from a peroxide complex to an organic substrate which could be utilized for the generation of anthracene endoperoxide in stoichiometric excess in a photo-catalytic reaction. 155 The substrate scope and mechanism of Rh 2 (cap) 4 -catalysed TBHP oxidation of phenol and aniline was discussed. The rate of oxidation of para-substituted phenols to 4-(t-butyldioxy)cyclohexadien ones increased significantly in aromatic hydrocarbon solvents.…”

Section: N Fementioning

confidence: 99%

“…In path 2, the formation of a transitory chelate (157) by H 3 N−BH 3 and al was fast; the elimination of NH 3 from (157) and subsequent formation of (156) was the slow step. The chelate (156) underwent a series of fast reactions before it was converted to (155). In methanol, MeOH BH 3 complex was formed initially followed by direct hydrogenation of the carbonyl compounds presumably via a single-step double H transfer.…”

Section: CLmentioning

confidence: 99%

Oxidation and Reduction

Mehrotra

2014

Organic Reaction Mechanisms Series

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A Rhodium Peroxido Complex in Mono‐, Di‐, and Peroxygenation Reactions

Cited by 37 publications

References 120 publications

Synthesis of an Iridium Peroxido Complex and Its Reactivity Towards Brønsted Acids

Synthesis of an Iridium Peroxido Complex and Its Reactivity Towards Brønsted Acids

Oxygen Reduction Mechanism of Monometallic Rhodium Hydride Complexes

Oxidation and Reduction

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