A Carbene‐Rich but Carbonyl‐Poor [Ir6(IMe)8(CO)2H14]2+ Polyhydride Cluster as a Deactivation Product from Catalytic Glycerol Dehydrogenation

Campos, Jesús; Sharninghausen, Liam S.; Crabtree, Robert H.; Balcells, David

doi:10.1002/ange.201407997

Cited by 11 publications

(2 citation statements)

References 54 publications

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“…By contrast, the transformation of organometallic complexes under reaction conditions can cause catalyst deactivation. This is shown with the evolution of a mononuclear Ir complex into Ir 6 clusters during the glycerol dehydrogenation reaction [26], which could be caused by the reduction of the mononuclear Ir complex by the product (H 2 ) or the reactant (glycerol).…”

Section: Evolution Of Molecular Metal Catalystsmentioning

confidence: 92%

Evolution of Isolated Atoms and Clusters in Catalysis

Liu

Corma

2020

Trends in Chemistry

162

134

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Structural evolution of isolated metal atoms and metal clusters with low atomicity is commonly observed in both homogeneous and heterogeneous catalysis. This evolution is directly associated with the formation of the working active sites and deactivation mechanism of the catalyst.Understanding the evolutional behavior of subnanometric metal catalysts can help to stabilize the active sites under harsh reaction conditions. Regeneration of the deactivated metal catalyst also relies on atomic-level understanding of the dynamic structural transformation processes.

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Section: Evolution Of Molecular Metal Catalystsmentioning

confidence: 92%

Evolution of Isolated Atoms and Clusters in Catalysis

Liu

Corma

2020

Trends in Chemistry

162

134

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“…Both are so inert that they do not lose hydrogen even at 140 °C and were likely formed from the small fraction of glyceraldehyde in the tautomeric equilibrium from catalytic glycerol dehydrogenation. 61,62 In earlier work, Aresta et al 42 suggest that this decarbonylative deactivation reaction impeded their ability to achieve more than a few turnovers for transfer hydrogenation of CO 2 from glycerol with their catalyst system. Similarly, Voutchkova-Kostal et al 33 find that a chelating Ru bis-NHC complex only retains full activity with i-PrOH as the H-donor solvent but not with glycerol.…”

Section: ■ Mechanismmentioning

confidence: 99%

Transfer Hydrogenation with Glycerol as H-Donor: Catalyst Activation, Deactivation and Homogeneity

Crabtree

2019

ACS Sustainable Chem. Eng.

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The title topic has risen to prominence with the increasing availability of the biomass-derived polyol, glycerol. Homogeneous precatalysts, particularly with the precious metals, have taken a role in these developments with promising initial results but with much yet to be done, notably in broadening the range of accessible valorization products and in moving to cheaper catalysts. The topics of catalyst activation, deactivation and homogeneity are particularly relevant here because of the relatively harsh conditions commonly employed in transfer hydrogenation from glycerol. This may therefore be a good field in which to address the problem of catalyst instability which has been considered the "Achilles heel" of homogeneous catalysis.

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Hierarchical Porous Organometallic Polymers Fabricated by Direct Knitting: Recyclable Single‐Site Catalysts with Enhanced Activity

et al. 2019

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supported catalysts by simply knitting rigid aromatic ligands via hypercross-linking (Friedel-Crafts reactions) has recently been proposed. [13] After further postmodification/activation, several MCPPs have been successfully developed. [14][15][16][17] However, with postmodification, avoiding the problems, like low density of catalytic sites due to incomplete modification and random/ nonselective metal anchoring, can be difficult. These issues may still lead to low catalytic activity and selectivity, especially in some challenging transformations. [18] In light of N-heterocyclic carbene-metal (NHC-M) complexes can act as robust and viable catalysts in a broad range of reactions, [19][20][21][22][23][24][25][26][27][28] various strategies have been developed for their immobilization. [29,30] Among them, selfsupporting strategy may represent one of the most practical and efficient approaches. [31][32][33][34] It has to be noted that NHC ligands still have to be carefully designed and modified before selfsupporting. Alternatively, the high catalytic activities and robustness of NHC-M complexes make them perfect candidates for direct knitting. To the best of our knowledge, there are only two reported examples on MCPPs in which the NHC ligands are firstly knitted and then coordinated to active metal ions (postmodification approach). [14,15] Direct knitting of NHC-M complexes to fabricate porous organometallic polymers (POMPs) that do not require postmodification/activation is still unknown.Herein, we have designed and prepared a series of unprecedented porous organometallic polymers POMPs-NHC-M 1-3 via direct knitting three types of bis-chelating NHC-M complexes (M = Ir, Pd, and Ru, Figure 1a). Using this facile strategy, which does not require postmodification/activation, 1) the metal active sites are atomically dispersed in the hierarchical porous matrix, and 2) the intrinsic well-defined bis-chelating mode and their molecular catalytic properties are maximally retained, which allows 3) the precise design and control of the immobilized catalysts at the molecular level. The advantages of direct knitting allow the resulting POMPs-NHC-M 1-3 to behave as recyclable solid single-site catalysts and exhibit extremely high catalytic activities in both hydrogenation and dehydrogenation reactions.In light of their robustness toward Friedel-Crafts reaction conditions, bis-chelating NHC-M (Ir, Pd and Ru) complexes 4, 5 and 6, derived from corresponding benzimidazolium salts, [24,25,27] were selected to fabricate POMPs via direct knitting with benzene ( Figure 1a). Concerning the plausible impact Porous organometallic polymers (POMPs) with hierarchical pore structures, high specific surface areas, and atomically dispersed metal (Ir, Pd, Ru) centers are successfully fabricated by a facile one-pot method through direct knitting of diverse N-heterocyclic carbene metal (NHC-M) complexes. These polymers can function as recyclable solid single-site catalysts and exhibit excellent catalytic activity and selectivity in both dehydrogenat...

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A Carbene‐Rich but Carbonyl‐Poor [Ir₆(IMe)₈(CO)₂H₁₄]²⁺ Polyhydride Cluster as a Deactivation Product from Catalytic Glycerol Dehydrogenation

Cited by 11 publications

References 54 publications

Evolution of Isolated Atoms and Clusters in Catalysis

Evolution of Isolated Atoms and Clusters in Catalysis

Transfer Hydrogenation with Glycerol as H-Donor: Catalyst Activation, Deactivation and Homogeneity

Hierarchical Porous Organometallic Polymers Fabricated by Direct Knitting: Recyclable Single‐Site Catalysts with Enhanced Activity

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