The novel electrophilic organo‐tantalum catalyst AlS/TaNpx(
Polyolefins comprise a major fraction of single-use plastics, yet their catalytic deconstruction/recycling has proven challenging due to their inert saturated hydrocarbon connectivities. Here a very electrophilic, formally cationic earth-abundant single-site organozirconium catalyst chemisorbed on a highly Brønsted acidic sulfated alumina support and characterized by a broad array of experimental and theoretical techniques, is shown to mediate the rapid hydrogenolytic cleavage of molecular and macromolecular saturated hydrocarbons under mild conditions, with catalytic onset as low as 90 °C/0.5 atm H2with 0.02 mol% catalyst loading. For polyethylene, quantitative hydrogenolysis to light hydrocarbons proceeds within 48 min with an activity of > 4000 mol(CH2units)·mol(Zr)−1·h−1at 200 °C/2 atm H2pressure. Under similar solventless conditions, polyethylene-
- NSF-PAR ID:
- 10381695
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 13
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 1 ) (Np=neopentyl) is prepared by chemisorption of the alkylidene Np3Ta=CHtBu onto highly Brønsted acidic sulfated alumina (AlS). The proposed catalyst structure is supported by EXAFS, XANES, ICP, DRIFTS, elemental analysis, and SSNMR measurements and is in good agreement with DFT analysis. Catalyst1 is highly effective for the hydrogenolysis of diverse linear and branched hydrocarbons, ranging from C2 to polyolefins. To the best of our knowledge,1 exhibits one of the highest polyolefin hydrogenolysis activities (9,800 (CH2units) ⋅ mol(Ta)−1 ⋅ h−1at 200 °C/17 atm H2) reported to date in the peer‐reviewed literature. Unlike the AlS/ZrNp2analog, the Ta catalyst is more thermally stable and offers multiple potential C−C bond activation pathways. For hydrogenolysis, AlS/TaNpxis effective for a wide variety of pre‐ and post‐consumer polyolefin plastics and is not significantly deactivated by standard polyolefin additives at typical industrial concentrations. -
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Abstract The novel electrophilic organo‐tantalum catalyst AlS/TaNpx(
1 ) (Np=neopentyl) is prepared by chemisorption of the alkylidene Np3Ta=CHtBu onto highly Brønsted acidic sulfated alumina (AlS). The proposed catalyst structure is supported by EXAFS, XANES, ICP, DRIFTS, elemental analysis, and SSNMR measurements and is in good agreement with DFT analysis. Catalyst1 is highly effective for the hydrogenolysis of diverse linear and branched hydrocarbons, ranging from C2 to polyolefins. To the best of our knowledge,1 exhibits one of the highest polyolefin hydrogenolysis activities (9,800 (CH2units) ⋅ mol(Ta)−1 ⋅ h−1at 200 °C/17 atm H2) reported to date in the peer‐reviewed literature. Unlike the AlS/ZrNp2analog, the Ta catalyst is more thermally stable and offers multiple potential C−C bond activation pathways. For hydrogenolysis, AlS/TaNpxis effective for a wide variety of pre‐ and post‐consumer polyolefin plastics and is not significantly deactivated by standard polyolefin additives at typical industrial concentrations. -
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K a25–35 in DMSO) benzylic and heterobenzylic C(sp3)−H bonds with aryl bromides has been achieved. This system is applicable to a range of pro‐nucleophiles for access to sterically and electronically diverse α‐aryl or α,α‐diaryl ketones, which are ubiquitous substructures in biologically active compounds. The Josiphos SL‐J001‐1‐based palladium catalyst was identified as the most efficient and selective, enabling carbonylative arylation with aryl bromides under 1 atm CO to provide the ketone products without the formation of direct coupling byproducts. Additionally, (Josiphos)Pd(CO)2was identified as the catalyst resting state. A kinetic study suggests that the oxidative addition of aryl bromides is the turnover‐limiting step. Key catalytic intermediates were also isolated. -
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Abstract A novel, selective and high‐yielding palladium‐catalyzed carbonylative arylation of a variety of weakly acidic (p
K a25–35 in DMSO) benzylic and heterobenzylic C(sp3)−H bonds with aryl bromides has been achieved. This system is applicable to a range of pro‐nucleophiles for access to sterically and electronically diverse α‐aryl or α,α‐diaryl ketones, which are ubiquitous substructures in biologically active compounds. The Josiphos SL‐J001‐1‐based palladium catalyst was identified as the most efficient and selective, enabling carbonylative arylation with aryl bromides under 1 atm CO to provide the ketone products without the formation of direct coupling byproducts. Additionally, (Josiphos)Pd(CO)2was identified as the catalyst resting state. A kinetic study suggests that the oxidative addition of aryl bromides is the turnover‐limiting step. Key catalytic intermediates were also isolated.
