skip to main content


This content will become publicly available on August 22, 2025

Title: Reductive samarium (electro)catalysis enabled by Sm III -alkoxide protonolysis

Samarium diiodide (SmI2) is a privileged, single-electron reductant deployed in diverse synthetic settings. However, generalizable methods for catalytic turnover remain elusive because of the well-known challenge associated with cleaving strong SmIII–O bonds. Prior efforts have focused on the use of highly reactive oxophiles to enable catalyst turnover. However, such approaches give rise to complex catalyst speciation and intrinsically limit the synthetic scope. Herein, we leveraged a mild and selective protonolysis strategy to achieve samarium-catalyzed, intermolecular reductive cross-coupling of ketones and acrylates with broad scope. The modularity of our approach allows rational control of selectivity based on solvent, pKa(whereKais the acid dissociation constant), and the samarium coordination sphere and provides a basis for future developments in catalytic and electrocatalytic lanthanide chemistry.

 
more » « less
Award ID(s):
2002158
PAR ID:
10535434
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
American Association for the Advancement of Science
Date Published:
Journal Name:
Science
Volume:
385
Issue:
6711
ISSN:
0036-8075
Page Range / eLocation ID:
847 to 853
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    A novel, selective and high‐yielding palladium‐catalyzed carbonylative arylation of a variety of weakly acidic (pKa25–35 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.

     
    more » « less
  2. Abstract

    A novel, selective and high‐yielding palladium‐catalyzed carbonylative arylation of a variety of weakly acidic (pKa25–35 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.

     
    more » « less
  3. Abstract

    Jeffbenite (Mg3Al2Si3O12) is a tetragonal phase found in so far only in superdeep diamonds, and its thermoelastic parameters are a prerequisite for determining entrapment pressures as it is regarded as a potential indicator for superdeep diamonds. In this study, the thermoelastic properties of synthetic Fe3+‐jeffbenite were measured up to 33.7 GPa and 750 K. High‐temperature static compression data were fitted, giving (∂KT0/T)P = −0.0107 (4) GPa/K andαT = 3.50 (3) × 10−5 K−1. The thermoelastic properties and phase stability are applied to modeling isomekes, orP‐Tpaths intersecting possible conditions of entrapment in diamond. We calculate that under ideal exhumation, jeffbenite entrapped at mantle transition zone conditions will exhibit a high remnant pressure at 300 K (Pinc) of ∼5.0 GPa. Elastic geobarometry on future finds of jeffbenite inclusions can use the new equation of state to estimate entrapment pressures for this phase with still highly uncertain stability field in the mantle.

     
    more » « less
  4. Abstract

    A series of molecular Mn catalysts featuring aniline groups in the second‐coordination sphere has been developed for electrochemical and photochemical CO2reduction. The arylamine moieties were installed at the 6 position of 2,2’‐bipyridine (bpy) to generate a family of isomers in which the primary amine is located at theortho‐(1‐Mn),meta‐(2‐Mn), orpara‐site (3‐Mn) of the aniline ring. The proximity of the second‐sphere functionality to the active site is a critical factor in determining catalytic performance. Catalyst1‐Mn, possessing the shortest distance between the amine and the active site, significantly outperformed the rest of the series and exhibited a 9‐fold improvement in turnover frequency relative to parent catalyst Mn(bpy)(CO)3Br (901 vs. 102 s−1, respectively) at 150 mV lower overpotential. The electrocatalysts operated with high faradaic efficiencies (≥70 %) for CO evolution using trifluoroethanol as a proton source. Notably, under photocatalytic conditions, a concentration‐dependent shift in product selectivity from CO (at high [catalyst]) to HCO2H (at low [catalyst]) was observed with turnover numbers up to 4760 for formic acid and high selectivities for reduced carbon products.

     
    more » « less
  5. Abstract

    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-co−1-octene, isotactic polypropylene, and a post-consumer food container cap are rapidly hydrogenolyzed to low molecular mass hydrocarbons. Regarding mechanism, theory and experiment identify a turnover-limiting C-C scission pathway involvingß-alkyl transfer rather than the more common σ-bond metathesis.

     
    more » « less