Partial Deoxygenation of Glycerol Catalyzed by Iridium Pincer Complexes

Lao, David; Owens, Alisa C. E.; Heinekey, D. Michael; Goldberg, Karen I.

doi:10.1021/cs400551g

Cited by 53 publications

(69 citation statements)

References 26 publications

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“…We previously reported the five coordinate complex [ (tBu)4 (POCOP)Ir(CO)(H)]BArF 20 ( 1 ) [BArF 20 = B(C 6 F 5 ) 4 ] and reported our failure to observe coordination of hydrogen (under 8 atm of H 2 ) to the open site trans to the iridium–hydride . Additionally, we found that low temperature protonation of the Ir(III) trans -dihydride (tBu)4 (POCOP)Ir(CO)(H) 2 gave rapid evolution of hydrogen . We were unable to directly detect the dihydrogen complex which is proposed as an intermediate in the mechanism for our Ir catalyzed glycerol deoxygenation …”

Section: Resultsmentioning

confidence: 86%

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Detection of an Iridium–Dihydrogen Complex: A Proposed Intermediate in Ionic Hydrogenation

Goldberg

Heinekey

et al. 2017

J. Am. Chem. Soc.

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Addition of high pressures of H to five-coordinate [(POCOP)Ir(CO)(H)]OTf [(POCOP) = κ-CH-2,6-(OP(Bu))] complexes results in observation of two new iridium-dihydrogen complexes. If the aryl moiety of the POCOP ligand is substituted with an electron withdrawing protonated dimethylamino group at the para position, hydrogen coordination is enhanced. Five-coordinate Ir-H complexes generated by addition of triflic acid to (POCOP)Ir(CO) species show an Ir-HH NMR chemical shift dependence on the number of equivalents of acid present. It is proposed that excess triflic acid in solution facilitates triflate dissociation from iridium, resulting in unsaturated five-coordinate Ir-H complexes. The five-coordinate iridium-hydride complexes were found to catalyze H/D exchange between H and CDOD. The existence of the dihydrogen complexes, as well as isotope exchange reactions, provide evidence for proposed ionic hydrogenation intermediates for glycerol deoxygenation.

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Section: Resultsmentioning

confidence: 86%

“…We previously showed that (tBu)4 (POCOP)Ir(CO) [ (tBu)4 (POCOP) = κ 3 -C 6 H 3 -2,6-(OP( t Bu) 2 ) 2 ] complexes could selectively catalyze the deoxygenation of glycerol to 1,3-propanediol and 1-propanol . The former is a useful precursor for the production of polyesters, and the latter is a potential fuel building block .…”

Section: Introductionmentioning

confidence: 99%

Detection of an Iridium–Dihydrogen Complex: A Proposed Intermediate in Ionic Hydrogenation

Goldberg

Heinekey

et al. 2017

J. Am. Chem. Soc.

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“…13,14 Carbon monoxide has been long known to coordinatively add to both PC(sp 2 )P- 15 and PC(sp 3 )P-supported 16 iridium(III) complexes, and such iridium carbonyl complexes have later been found to be involved in catalytic transformations such as transfer hydrogenations of ketones 8 and olen hydroformylation. 17 PCP iridium(I) carbonyl complexes are well known for benzene based pincer structures, 7,[18][19][20][21][22] and have been reported to catalyse the decarbonylation of 2-naphtaldehyde 23 and the partial deoxygenation of diols 24 and glycerol, 25 but there are no PC(sp 3 ) P-supported iridium(I) carbonyl complexes reported to this date.…”

Section: Introductionmentioning

confidence: 99%

PC(sp³)P pincer carbonyl complexes of iridium(i), and iridium(iii)

2015

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The previously reported complex trans-[IrHCl{cis-1,3-bis-(di-tert-butylphosphino)methyl}cyclohexane] (2) forms the 18-electron carbonyl compound anti-[Ir(CO)HCl{cis-1,3-bis-((di-tert-butylphosphino)methyl)} cyclohexane] (5a) upon reaction with 1 atm CO. The structural isomer syn-[IrH(CO)Cl{cis-1,3-bis-((ditert-butylphosphino)methyl)}cyclohexane] (5b) is obtained directly upon complexation of the ligand (1) with IrCl 3 $H 2 O in refluxing DMF. syn-5b is the first iridium aliphatic pincer complex with this orientation of the hydrogens and is the thermodynamically more stable isomer. Both compounds 5a and 5b afford the Ir(I) complex trans-[Ir(CO){cis-1,3-bis-((di-tert-butylphosphino)methyl)}cyclohexane] (4) upon treatment with KO t Bu. Complex 4 was also synthesised in a more straightforward fashion from the previously known terminal nitrogen complex trans-[Ir(N 2 ){cis-1,3-bis-((di-tert-butylphosphino)-methyl)} cyclohexane] (3) under atmospheric CO. The complexes 4, 5a and 5b were characterised spectroscopically and in the solid state. IR data point to a more electron rich metal centre as compared to the corresponding aromatic complexes.

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“…Therefore over-hydrogenolysis to propanols and even propane can proceed over the catalysts that can work by the dehydration + hydrogenation route. Homogeneous Ru and Ir complexes combined with external acid are typical catalysts for production of propanols or propane from glycerol [10,11] and 1,2-PrD [12][13][14]. In contrast, under more basic conditions over heterogeneous metal catalysts, the dehydrogenation + dehydration + hydrogenation route is preferred to the dehydration + hydrogenation route.…”

Section: Conventional Hydrogenolysis Of Glycerol and Tetrahydrofurfurmentioning

confidence: 99%

Selective Hydrogenolysis of C–O Bonds Using the Interaction of the Catalyst Surface and OH Groups

Tomishige

Nakagawa

Tamura

2014

Topics in Current Chemistry

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Hydrogenolysis of C-O bonds is becoming more and more important for the production of biomass-derived chemicals. Since substrates originated from biomass usually have high oxygen content and various kinds of C-O bonds, selective hydrogenolysis is required. Rhenium or molybdenum oxide modified rhodium and iridium metal catalysts (Rh-ReO(x), Rh-MoO(x), and Ir-ReO(x)) have been reported to be effective for selective hydrogenolysis. This review introduces the catalytic performance and reaction kinetics of Rh-ReO(x), Rh-MoO(x), and Ir-ReO(x) in the hydrogenolysis of various substrates, where selectivity is especially characteristic. Based the model structure of the catalysts and the reaction mechanism, the role of the oxide components is to make the interaction between the OH groups in the substrates and the catalyst surface, and the role of metal components is to dissociate hydrogen molecule heterolytically to give hydride and proton.

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Partial Deoxygenation of Glycerol Catalyzed by Iridium Pincer Complexes

Cited by 53 publications

References 26 publications

Detection of an Iridium–Dihydrogen Complex: A Proposed Intermediate in Ionic Hydrogenation

Detection of an Iridium–Dihydrogen Complex: A Proposed Intermediate in Ionic Hydrogenation

PC(sp³)P pincer carbonyl complexes of iridium(i), and iridium(iii)

Selective Hydrogenolysis of C–O Bonds Using the Interaction of the Catalyst Surface and OH Groups

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Partial Deoxygenation of Glycerol Catalyzed by Iridium Pincer Complexes

Cited by 53 publications

References 26 publications

Detection of an Iridium–Dihydrogen Complex: A Proposed Intermediate in Ionic Hydrogenation

Detection of an Iridium–Dihydrogen Complex: A Proposed Intermediate in Ionic Hydrogenation

PC(sp3)P pincer carbonyl complexes of iridium(i), and iridium(iii)

Selective Hydrogenolysis of C–O Bonds Using the Interaction of the Catalyst Surface and OH Groups

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PC(sp³)P pincer carbonyl complexes of iridium(i), and iridium(iii)