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1. Encapsulation of tricopper cluster in a synthetic cryptand enables facile redox processes from Cu ^I Cu ^I Cu ^I to Cu ^II Cu ^II Cu ^II states

   https://doi.org/10.1039/D0SC05441K  

   Zhang, Weiyao; Moore, Curtis E.; Zhang, Shiyu (March 2021, Chemical Science)

   null (Ed.)

   One-pot reaction of tris(2-aminoethyl)amine (TREN), [Cu I (MeCN) 4 ]PF 6 , and paraformaldehyde affords a mixed-valent [ TREN4 Cu II Cu I Cu I (μ 3 -OH)](PF 6 ) 3 complex. The macrocyclic azacryptand TREN4 contains four TREN motifs, three of which provide a bowl-shape binding pocket for the [Cu 3 (μ 3 -OH)] 3+ core. The fourth TREN caps on top of the tricopper cluster to form a cryptand, imposing conformational constraints and preventing solvent interaction. Contrasting the limited redox capability of synthetic tricopper complexes reported so far, [ TREN4 Cu II Cu I Cu I (μ 3 -OH)](PF 6 ) 3 exhibits several reversible single-electron redox events. The distinct electrochemical behaviors of [ TREN4 Cu II Cu I Cu I (μ 3 -OH)](PF 6 ) 3 and its solvent-exposed analog [ TREN3 Cu II Cu II Cu II (μ 3 -O)](PF 6 ) 4 suggest that isolation of tricopper core in a cryptand enables facile electron transfer, allowing potential application of synthetic tricopper complexes as redox catalysts. Indeed, the fully reduced [ TREN4 Cu I Cu I Cu I (μ 3 -OH)](PF 6 ) 2 can reduce O 2 under acidic conditions. The geometric constraints provided by the cryptand are reminiscent of Nature's multicopper oxidases (MCOs). For the first time, a synthetic tricopper cluster was isolated and fully characterized at Cu I Cu I Cu I ( 4a ), Cu II Cu I Cu I ( 4b ), and Cu II Cu II Cu I ( 4c ) states, providing structural and spectroscopic models for many intermediates in MCOs. Fast electron transfer rates (10 5 to 10 6 M −1 s −1 ) were observed for both Cu I Cu I Cu I /Cu II Cu I Cu I and Cu II Cu I Cu I /Cu II Cu II Cu I redox couples, approaching the rapid electron transfer rates of copper sites in MCO. 

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2. Theoretical Insights into H ₂ Activation over Anatase TiO ₂ Supported Metal Adatoms

   https://doi.org/10.1021/acscatal.3c04201  

   Li, Qiang; Yan, George; Vlachos, Dionisios G (January 2024, ACS Catalysis)

   H2 activation is fundamental in catalysis. Single-atom catalysts (SACs) can be highly selective hydrogenation catalysts due to their tunable geometric and electronic properties. In this work, H2 activation (adsorption, splitting, and diffusion) on the anatase TiO2-supported SAC has been modeled in detail. The stable configurations of 14 transition metals from 3d to 5d (Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Os, Ir, Pt, and Au) and Sn have been screened. We compared H and H2 adsorption and H2 heterolytic and homolytic splitting on SA/TiO2. H on the SAC in neutral, hydridic, and proton forms and the preferred H2 dissociation paths are revealed. We found that the metal adatoms strengthen the Brønsted acids via forming the SA-O bonds and promote the H adsorption on Ti sites via forming the Ti3+ sites. The electronic descriptor using the energy level of the frontier d orbital, referenced to vacuum, can predict the single H and H2 dissociative adsorption energies on the metal site. As the SA-Hδ- interaction is stronger than Ti-Hδ-, the activation barriers for heterolytic paths over SA-O sites are lower than over Ti-O sites. H2 adsorption is activated on Au, Ru, Rh, Pd, and Ir in a dihydrogen complex structure with an elongated H-H bond. Homolytic splitting over SA sites is favored thermodynamically and kinetically on Rh, Pd, Os, Ir, and Pt. In contrast, for the remaining SA/TiO2, H-H splitting at the SA-O is kinetically favored compared to the Ti-O sites, but the products are less thermodynamically favored. 

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3. Expansion of the (BB)Ru metallacycle with coinage metal cations: formation of B–M–Ru–B (M = Cu, Ag, Au) dimetalacyclodiboryls

   https://doi.org/10.1039/C8SC00190A  

   Eleazer, Bennett J.; Smith, Mark D.; Popov, Alexey A.; Peryshkov, Dmitry V. (January 2018, Chemical Science)

   In this work, we introduce a novel approach for the selective assembly of heterometallic complexes by unprecedented coordination of coinage metal cations to strained single ruthenium–boron bonds on a surface of icosahedral boron clusters. M( i ) cations (M = Cu, Ag, and Au) insert into B–Ru bonds of the (BB)–carboryne complex of ruthenium with the formation of four-membered B–M–Ru–B metalacycles. Results of theoretical calculations suggest that bonding within these metalacycles can be best described as unusual three-center-two-electron B–M⋯Ru interactions that are isolobal to B–H⋯Ru borane coordination for M = Cu and Ag, or the pairs of two-center-two electron B–Au and Au–Ru interactions for M = Au. These transformations comprise the first synthetic route to exohedral coinage metal boryl complexes of icosahedral closo -{C 2 B 10 } clusters, which feature short Cu–B (2.029(2) Å) and Ag–B (2.182(3) Å) bonds and the shortest Au–B bond (2.027(2) Å) reported to date. The reported heterometallic complexes contain Cu( i ) and Au( i ) centers in uncharacteristic square-planar coordination environments. These findings pave the way to rational construction of a broader class of multimetallic architectures featuring M–B bonds. 

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4. Zerovalent Triphosphine Ruthenium Complexes for Coupling Carbon Dioxide and Ethylene

   https://doi.org/10.1021/acs.organomet.4c00433  

   Adamson, Tristan T; Reeder, Laura G; Kelley, Steven P; Bernskoetter, Wesley H (January 2025, Organometallics)

   The coupling of carbon dioxide and ethylene to generate value added chemicals has been part of recent fundamental advances to improve sustainability in commercial chemical synthons. A formal zerovalent triphosphine ligated ruthenium complex, (tBuP(CH2CH2PEt2)2)Ru(κ-S-DMSO)(C2H4), was found to promote CO2 activation, affording products derived from both a 1:1 and 1:2 ethylene to CO2 coupling stoichiometry. The equimolecular coupling reaction selectively afforded a five-membered ruthenium lactone species, (tBuP(CH2CH2PEt2)2)Ru(κ-S-DMSO)(κ-C,κ-O-CH2CH2CO2), under low CO2 pressure. At higher CO2 pressure, the ruthenium lactone complex activated a second equivalent of CO2, yielding a dimeric methylmalonate ruthenium compound, [(tBuP(CH2CH2PEt2)2)Ru(μ2, κ1-O, κ2-O,O-O2CCHCH3CO2)]2. Both carbon dioxide activation products were characterized by X-ray diffraction. Preliminary mechanistic studies suggest that reversible β-H elimination is a key process in conversion between the two ruthenium carboxylate species. A rare formally zerovalent ruthenium coordination compound stabilized only by ethylene and DMSO ligands was also isolated and characterized. 

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5. Enantioconvergent Chan–Evans–Lam C(sp ³ )–O Coupling: Cu-Catalyzed Asymmetric Benzyl- and Allylborane Oxidation

   https://doi.org/10.1021/jacs.6c02555  

   Schubert, Tanner J; Carpentier, Ambre; Li, Yongxian; Hubbell, Kolter C; Oh, Jeewhan; Zheng, Shao-Liang; Paton, Robert S; Dong, Yuyang (May 2026, Journal of the American Chemical Society)

   While alkylborane oxidation constitutes one of the most widely utilized strategies to construct C–O bonds, asymmetric versions of this transformation remain elusive. Establishing such an asymmetric approach would unlock a strategically distinct disconnection to oxygen-bearing stereogenic centers, which are ubiquitous across biologically active scaffolds. Herein, we employ a Cu-catalyzed single-electron mechanism to achieve enantioconvergent alkylborane oxidation for the first time. The central challenge─suppressing the unselective carbocation pathway from alkyl radical oxidation by the Cu(II)–carboxylate─is addressed by (1) lowering the reaction temperature to attenuate the undesired radical–polar crossover while (2) leveraging photochemical activation to preserve the single-electron radical functionalization manifold. The reaction exhibits broad functional-group compatibility, engaging benzyl- and allylboronic esters; diverse carboxylic acids, including complex pharmaceutical substructures and heterocycle-containing substrates, are also well tolerated. The reported protocol is scalable to gram quantities and was utilized for the asymmetric synthesis of an immunosuppressant drug candidate. Mechanistic studies, including stoichiometric interrogation of elementary steps, rate law determination, radical trapping experiments, and density functional theory (DFT) computations, indicate that the reaction operates by balancing two light-driven processes: (1) rate-determining N–H bond homolysis followed by N-radical-mediated C–B bond activation and (2) enantioselective Cu-mediated radical functionalization via an inner-sphere pathway. The reactive Cu(II)–carboxylate intermediate was isolated and structurally characterized, permitting direct examination of its spectroscopic features and radical-trapping reactivity. Electron paramagnetic resonance (EPR) studies identified the Cu(II)–carboxylate species as the catalyst resting state, and stoichiometric reaction of the Cu(II)–carboxylate with a persistent trityl radical demonstrated its competency for C–O bond formation. Hammett analysis further revealed that the efficiency of C–O bond formation is governed by the electrophilicity of the Cu(II)–carboxylate intermediate. 

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