Lanthanide triflates have been used to incorporate NdIIIand SmIIIions into the 2.2.2‐cryptand ligand (crypt) to explore their reductive chemistry. The Ln(OTf)3complexes (Ln=Nd, Sm; OTf=SO3CF3) react with crypt in THF to form the THF‐soluble complexes [LnIII(crypt)(OTf)2][OTf] with two triflates bound to the metal encapsulated in the crypt. Reduction of these LnIII‐in‐crypt complexes using KC8in THF forms the neutral LnII‐in‐crypt triflate complexes [LnII(crypt)(OTf)2]. DFT calculations on [NdII(crypt)]2+], the first NdIIcryptand complex, assign a 4f4electron configuration to this ion.
Electrophotocatalytic perfluoroalkylation by LMCT excitation of Ag(II) perfluoroalkyl carboxylates
Molecular Ag(II) complexes are superoxidizing photoredox catalysts capable of generating radicals from redox-reticent substrates. In this work, we exploited the electrophilicity of Ag(II) centers in [Ag(bpy)2(TFA)][OTf] and Ag(bpy)(TFA)2(bpy, 2,2′-bipyridine; OTf, CF3SO3–) complexes to activate trifluoroacetate (TFA) by visible light–induced homolysis. The resulting trifluoromethyl radicals may react with a variety of arenes to forge C(sp2)–CF3bonds. This methodology is general and extends to other perfluoroalkyl carboxylates of higher chain length (RFCO2–; RF, CF2CF3or CF2CF2CF3). The photoredox reaction may be rendered electrophotocatalytic by regenerating the Ag(II) complexes electrochemically during irradiation. Electrophotocatalytic perfluoroalkylation of arenes at turnover numbers exceeding 20 was accomplished by photoexciting the Ag(II)–TFA ligand-to-metal charge transfer (LMCT) state, followed by electrochemical reoxidation of the Ag(I) photoproduct back to the Ag(II) photoreactant.
more » « less- PAR ID:
- 10528475
- Publisher / Repository:
- Science
- Date Published:
- Journal Name:
- Science
- Volume:
- 383
- Issue:
- 6680
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- 279 to 284
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract -
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Abstract Lanthanide triflates have been used to incorporate NdIIIand SmIIIions into the 2.2.2‐cryptand ligand (crypt) to explore their reductive chemistry. The Ln(OTf)3complexes (Ln=Nd, Sm; OTf=SO3CF3) react with crypt in THF to form the THF‐soluble complexes [LnIII(crypt)(OTf)2][OTf] with two triflates bound to the metal encapsulated in the crypt. Reduction of these LnIII‐in‐crypt complexes using KC8in THF forms the neutral LnII‐in‐crypt triflate complexes [LnII(crypt)(OTf)2]. DFT calculations on [NdII(crypt)]2+], the first NdIIcryptand complex, assign a 4f4electron configuration to this ion.
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Abstract Visible‐light capture activates a thermodynamically inert CoIII−CF3bond for direct C−H trifluoromethylation of arenes and heteroarenes. New trifluoromethylcobalt(III) complexes supported by a redox‐active [OCO] pincer ligand were prepared. Coordinating solvents, such as MeCN, afford green, quasi‐octahedral [(SOCO)CoIII(CF3)(MeCN)2] (
2 ), but in non‐coordinating solvents the complex is red, square pyramidal [(SOCO)CoIII(CF3)(MeCN)] (3 ). Both are thermally stable, and2 is stable in light. But exposure of3 to low‐energy light results in facile homolysis of the CoIII−CF3bond, releasing.CF3radical, which is efficiently trapped by TEMPO.or (hetero)arenes. The homolytic aromatic substitution reactions do not require a sacrificial or substrate‐derived oxidant because the CoIIby‐product of CoIII−CF3homolysis produces H2. The photophysical properties of2 and3 provide a rationale for the disparate light stability. -
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Abstract Chloride abstraction from [(
R ,R )‐(iPrDuPhos)Co(μ‐Cl)]2with NaBArF4(BArF4=B[(3,5‐(CF3)2)C6H3]4) in the presence of dienes, such as 1,5‐cyclooctadiene (COD) or norbornadiene (NBD), yielded long sought‐after cationic bis(phosphine) cobalt complexes, [(R ,R )‐(iPrDuPhos)Co(η2,η2‐diene)][BArF4]. The COD complex proved substitutionally labile undergoing diene substitution with tetrahydrofuran, NBD, or arenes. The resulting 18‐electron, cationic cobalt(I) arene complexes, as well as the [(R ,R )‐(iPrDuPhos)Co(diene)][BArF4] derivatives, proved to be highly active and enantioselective precatalysts for asymmetric alkene hydrogenation. A cobalt–substrate complex, [(R ,R )‐(iPrDuPhos)Co(MAA)][BArF4] (MAA=methyl 2‐acetamidoacrylate) was crystallographically characterized as the opposite diastereomer to that expected for productive hydrogenation demonstrating a Curtin–Hammett kinetic regime similar to rhodium catalysis. -
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Abstract Chloride abstraction from [(
R ,R )‐(iPrDuPhos)Co(μ‐Cl)]2with NaBArF4(BArF4=B[(3,5‐(CF3)2)C6H3]4) in the presence of dienes, such as 1,5‐cyclooctadiene (COD) or norbornadiene (NBD), yielded long sought‐after cationic bis(phosphine) cobalt complexes, [(R ,R )‐(iPrDuPhos)Co(η2,η2‐diene)][BArF4]. The COD complex proved substitutionally labile undergoing diene substitution with tetrahydrofuran, NBD, or arenes. The resulting 18‐electron, cationic cobalt(I) arene complexes, as well as the [(R ,R )‐(iPrDuPhos)Co(diene)][BArF4] derivatives, proved to be highly active and enantioselective precatalysts for asymmetric alkene hydrogenation. A cobalt–substrate complex, [(R ,R )‐(iPrDuPhos)Co(MAA)][BArF4] (MAA=methyl 2‐acetamidoacrylate) was crystallographically characterized as the opposite diastereomer to that expected for productive hydrogenation demonstrating a Curtin–Hammett kinetic regime similar to rhodium catalysis.
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- Journal Article:
- https://doi.org/10.1126/science.adk4919
