Copper Hydride Research Articles

DFT Study on Copper‐Catalyzed Hydroboration of 1,3‐Diynes: Mechanism, Selectivity, and Comparison with Ruthenium

Density functional theory calculations have been performed to explore the mechanism of copper‐catalyzed hydroboration of 1,3‐diyne with HBpin. The catalytic cycles are composed of three elementary processes in succession, namely, the generation of copper hydride species, migratory insertion and σ‐bond metathesis, among which the σ‐bond metathesis step is rate‐determining with a free‐energy barrier of 19.7 kcal/mol. The syn‐addition selectivity originates from the high barrier for converting (Z)‐product to (E)‐product. Effects of diphosphine ligands and substituents on the reactivity were also addressed. Lastly, this copper‐catalyzed hydroboration was compared with a related ruthenium‐catalyzed one, and the obtained results indicated that copper‐catalyzed hydroboration has a more favorable σ‐bond metathesis step but more challenging migratory insertion step as compared to the ruthenium‐catalyzed counterpart. Wavefunction analyses were performed to understand the observed behaviors.

Mechanistic Investigation into Copper(I) Hydride Catalyzed Formic Acid Dehydrogenation.

Copper(I) hydride complexes are typically known to react with CO2 to form their corresponding copper formate counterparts. However, recently it has been observed that some multinuclear copper hydrides can feature the opposite reactivity and catalyze the dehydrogenation of formic acid. Here we report the use of a multinuclear PNNP copper hydride complex as an active (pre)catalyst for this reaction. Mechanistic investigations provide insights into the catalyst resting state and the rate-determining step and identify an off-cycle species that is responsible for the unexpected substrate inhibition in this reaction.

Structure Distortion Endows Copper Nanoclusters with Surface-Active Uncoordinated Sites for Boosting Catalysis.

The utilization of structure distortion to modulate the electronic structure and alter catalytic properties of metallic nanomaterials is a well-established practice, but accurately identifying and comprehensively understanding these distortions present significant challenges. Ligand-stabilized metal nanoclusters with well-defined structures serve as exemplary model systems to illustrate the structure chemistry of nanomaterials, among which few studies have investigated nanocluster models that incorporate structural distortions. In this work, a novel copper hydride nanocluster, Cu42(PPh3)8(RS)4(CF3COO)10(CH3O)4H10 (Cu42; PPh3 is triphenylphosphine and RSH is 2,4-dichlorophenylthiol), with a highly twisted structure has been synthesized in a simple way. Structural analysis reveals Cu42 comprises two Cu25 units that are conjoined in a nearly orthogonal manner. The dramatic distortion in the metal framework, which is driven by multiple interactions from the surface ligands, endows the cluster with a rich array of uncoordinated metal sites on the surface. The resulting cluster, as envisioned, exhibits remarkable activity in catalyzing carbonylation of anilines. The findings from this study not only provides atomically precise insights into the structural distortions that are pertinent to nanoparticle catalysts but also underscores the potential of structurally distorted NCs as a burgeoning generation of catalysts with precise structures and outstanding performances that can be tailored for specific functions.

Dearomative 1,2-Hydroamination of Nonactivated Arenes via Copper–Hydride Catalysis

Dearomative 1,2-Hydroamination of Nonactivated Arenes via Copper–Hydride Catalysis

Asymmetric Hydroacetalization of Vinyl Arenes under Copper Hydride Catalysis

Asymmetric Hydroacetalization of Vinyl Arenes under Copper Hydride Catalysis

Theoretical study of vibronic absorption spectra and Franck-Condon factors of copper and silver hydrides

The electronic absorption spectra of CuH and AgH molecules are calculated using the analytical expression for the spectral density related to the thermal dipole time correlation function. In addition, the vibronic transition probabilities between the initial and final states are determined by calculating the transition dipole moments and the Franck-Condon factors using the LEVEL program. The spectroscopic constants recently obtained from MRCI + SOC calculations are used to calculate the absorption spectral line shapes of CuH and AgH molecules and plotted in the time and frequency domains for the vibronic transitions from the ground state Ω = 0+(I) to the excited states Ω = 0+(II), 0+(III), 1(I), 1(II), 1(III), and 1(IV) for CuH and to the excited states Ω = 0+(II), 0+(III), 0+(IV), 1(II), 1(III), 1(IV), 1(V), and 1(VI) for AgH.

Coproduction of Glycolic Acid and Hydrogen by Electroreforming Ethylene Glycol Using Palladium–Copper Hydride Hyperbranched Nanocrystals

Coproduction of Glycolic Acid and Hydrogen by Electroreforming Ethylene Glycol Using Palladium–Copper Hydride Hyperbranched Nanocrystals

Regioselective Condensation Polymerization of Propargylic Electrophiles Enabled by Catalytic Element-Cupration.

Here, we report a set of new polymerization reactions enabled by the 1,2-regioselective hydro- and silylcupration of enyne-type propargylic electrophiles. Highly regioregular head-to-tail poly(2-butyne-1,4-diyl)s (HT-PBD), bearing either methyl or silylmethyl side chains, are synthesized for the first time. A rapid entry into carbon-rich copolymers with adjustable silicon content is developed via in situ monomer bifurcation. Furthermore, a one-pot polymerization/semireduction sequence is developed to access a cis-poly(butadiene)-derived backbone by a ligand swap on copper hydride species. Interestingly, borocupration, typically exhibiting identical regioselectivity with its hydro- and silyl analogues, seems to proceed in a 3,4-selective manner. Computational studies suggest the possible role of the propargylic leaving group in this selectivity switch. This work presents a new class of regioregular sp-carbon-rich polymers and meanwhile a novel approach to organosilicon materials.

Copper hydride species activated hypophosphite hydrolysis towards litre-level and high-purity hydrogen production

Large-scale generation of high-purity hydrogen (H2) from simple hydrolysis strategy is vital, but the traditional technologies remain problems of economy and efficiency. Herein, a new and low-cost technical route is highlighted to realize the litre-level and efficient production of high-purity H2 from sodium hypophosphite (NaH2PO2) hydrolysis at room temperature. The formation and stabilization of CuH species on the designed Cu–Cu2O/CuH catalyst plays a key role in stimulating a continuous reversible NaH2PO2 hydrolysis cycle for H2. Impressively, this new technology achieves the high generated rate of 3.3 L h−1•cm−2 for H2 in alkaline media, which outperforms the other existing hydrolysis technologies. The proposed catalytic mechanism involves renewable CuH active species catalyzing the spontaneous reaction of NaH2PO2 and H2O to form H2 gas and phosphate. From the view of practical application, the developed coupling catalytic system also operates efficiently in deionized water, seawater and tap water solutions, shows unique interference immunity and high stability of convenient H2 generation.

Detection and Characterization of Hydride Ligands in Copper Complexes by Hard X-Ray Spectroscopy.

Transition metal complexes, particularly copper hydrides, play an important role in various catalytic processes and molecular inorganic chemistry. This study employs synchrotron hard X-ray spectroscopy to gain insights into the geometric and electronic properties of copper hydrides as potential catalysts for CO2 hydrogenation. The potential of high energy resolution X-ray absorption near-edge structure (HERFD-XANES) and valence-to-core X-ray emission (VtC-XES) is demonstrated with measurement on Stryker's reagent (Cu6H6) and [Cu3(μ3-H)(dpmppe)2](PF6)2 (Cu3H), alongside a non-hydride copper compound ICu(dtbppOH) (Cuy-I). The XANES analysis reveals that coordination geometries strongly influence the spectra, providing only indirect details about hydride coordination. The VtC-XES analysis exhibits a distinct signal around 8975 eV, offering a diagnostic tool to identify hydride ligands. Theoretical calculations support and extend these findings by comparing hydride-containing complexes with their hydride-free counterparts.

A heteroleptic Pt-doped Cu-rich hydrides nanocluster

An atomically precise heteroleptic Pt-doped Cu-rich hydride nanocluster [PtH2@Cu14(dtc)6(C2Ph)6] (PtH2Cu14-dtc) has been successfully synthesized. This was achieved by introducing a discrete Pt(II) precursor to the copper hydride nanocluster [Cu28H15(dtc)12](PF6) in the presence of terminal alkynes. The structure of PtH2Cu14 determined by X-ray diffraction reveals a bicapped icosahedral copper(I) cage encapsulating a linear platinum dihydride [PtH2]2- unit. The interstitial hydrides are arranged in a trigonal bipyramidal (tbp) geometry with a five-coordinated hydride as confirmed by 2H NMR and ESI-MS measurements.

Microfluidic Synthesis of CuH Nanoparticles for Antitumor Therapy through Hydrogen-Enhanced Apoptosis and Cuproptosis.

Cuproptosis has drawn enormous attention in antitumor material fields; however, the responsive activation of cuproptosis against tumors using nanomaterials with high atom utilization is still challenging. Herein, a copper-based nanoplatform consisting of acid-degradable copper hydride (CuH) nanoparticles was developed via a microfluidic synthesis. After coating with tumor-targeting hyaluronic acid (HA), the nanoplatform denoted as HA-CuH-PVP (HCP) shows conspicuous damage toward tumor cells by generating Cu+ and hydrogen (H2) simultaneously. Cu+ can induce apoptosis by relying on Fenton-like reactions and lead to cuproptosis by causing mitochondrial protein aggregation. Besides, the existence of H2 can enhance both cell death types by causing mitochondrial dysfunction and intracellular redox homeostatic disorders. In vivo experimental results further exhibit the desirable potential of HCP for killing tumor cells and inhibiting lung metastases, which will broaden the horizons of designing copper-based materials triggering apoptosis and cuproptosis for better antitumor efficacy.

Wittig-Type E-Selective Olefination of Imines with Vinyl Boronate Esters Under Copper Hydride Catalysis

Wittig-Type E-Selective Olefination of Imines with Vinyl Boronate Esters Under Copper Hydride Catalysis

The structure-activity relationship of copper hydride nanoclusters in hydrogenation and reduction reactions.

Copper hydrides are highly active catalysts in hydrogenation reactions and reduction processes. Three Stryker-type copper hydride nanoclusters (NCs), [(TPP)CuH]6, [(TCP)CuH]6 and [(TOP)CuH]6 (TPP = triphenylphosphine, TCP = tricyclohexylphosphine and TOP = tri-n-octylphosphine), were synthesized in this study. Due to variations in the electron-donating properties of the phosphine ligands, the UV-visible absorption spectra of the three NCs exhibited notable distinctions. The influence of the phosphine ligands on the effectiveness of the NCs as hydride sources in hydrogenation processes, as well as on the applicability as homogeneous catalysts for reduction reactions, was systematically studied. Due to the highest electron-donating properties of the TOP ligand, [(TOP)CuH]6 was found to exhibit superior performance in both hydrogenation reactions and catalytic reduction reactions. Moreover, these hydrophobic NCs worked well as heterogeneous catalysts in the reduction of 4-nitrophenol.

Continuous-flow copper hydride-catalyzed reduction of 2,1-benzoisoxazoles

Copper hydride catalysis was used for selective N,O-reduction of 2,1-benzoisoxazoles in continuous flow to access 2-aminobenzophenones, key intermediates and cost drivers in the synthesis of benzodiazepines.

Copper-Catalyzed Regio- and Enantioselective Hydroboration of Difluoroalkyl-Substituted Internal Alkenes.

Catalytic asymmetric hydroboration of fluoroalkyl-substituted alkenes is a straightforward approach to access chiral small molecules possessing both fluorine and boron atoms. However, enantioselective hydroboration of fluoroalkyl-substituted alkenes without fluorine elimination has been a long-standing challenge in this field. Herein, a copper-catalyzed hydroboration of difluoroalkyl-substituted internal alkenes with high levels of regio- and enantioselectivities is reported. The native carbonyl directing group, copper hydride system, and bisphosphine ligand play crucial roles in suppressing the undesired fluoride elimination. This atom-economic protocol provides a practical synthetic platform to obtain a wide scope of enantioenriched secondary boronates bearing the difluoromethylene moieties under mild conditions. Synthetic applications including functionalization of biorelevant molecules, versatile functional group interconversions, and preparation of difluoroalkylated Terfenadine derivative are also demonstrated.

Chiral Hydride Cu18 Clusters Transform to Superatomic Cu15Ag4 Clusters: Circularly Polarized Luminescence Lighting.

The manipulation of metal cluster enantiomers and their reconstruction remain challenging. Here, for the first time, we report an enantiomeric pair of hydride copper clusters [Cu18H(R/S-PEA)12](BF4)5 (R/S-Cu18H) made using designed chiral ligands. By manipulation of R/S-Cu18H with Ag+ ions, H- ions are released, leading to the reconstruction of 15 Cu atoms. Moreover, 4 Ag atoms replaced Cu atoms at the specific sites, resulting in the formation of homochiral [Cu15Ag4(R/S-PEA)12](BF4)5 (R/S-Cu15Ag4) with an isomorphic metal skeleton. This process was accompanied by a reduction reaction generating two free valence elections in the chiral alloying counterparts, which displayed orange emission. The solid-state R/S-Cu15Ag4 exhibited a photoluminescence quantum yield of 7.02% and excellent circularly polarized luminescence. The chiral transformations were resolved by single-crystal X-ray diffraction. The development of chiral copper hydride precursor-based metal clusters with chiroptical activities holds tremendous promise for advancing the field of optoelectronics and enabling new applications in lighting, displays, and beyond.

CuH-Catalyzed Selective N-Methylation of Amines Using Paraformaldehyde as a C1 Source.

Copper hydride (CuH) complexes have been proposed as key intermediates in synthesis and catalysis. Herein, we developed a highly efficient strategy for CuH-catalyzed N-methylation of aromatic and aliphatic amines using paraformaldehyde and polymethylhydrosiloxane (PMHS) under mild reaction conditions. The reaction proceeded smoothly without additives to furnish the corresponding N-methylated products using cyclic(alkyl)(amino)carbene (CAAC)CuH as a reaction intermediate, which results from a reaction between PMHS and (CAAC)CuCl.

Synthesis, Structural Characterization, and CO2 Reactivity of a Constitutionally Analogous Series of Tricopper Mono-, Di-, and Trihydrides.

The formation of hydrides at heterogeneous copper surfaces results in dramatic structural and reactivity changes, yet the morphologies of these materials and their respective roles in catalysis are not well understood. Of particular interest is the reactivity of heterogeneous copper hydrides with carbon dioxide (CO2), an early mechanistic branching point in the CO2 reduction reaction. Herein, we report the synthesis, characterization, and reactivity of tricopper compounds supported by a facially biased, chelating tris(carbene) ligand scaffold. This sterically bulky environment affords access to an isolable series of tricopper hydrides: [LCu3H]2+ (4), [LCu3H2]+ (3), and LCu3H3 (6). Single-crystal X-ray diffraction and solution NMR spectroscopy studies reveal both geometric flexibility within the Cu3 core and fluxionality of hydride ligands across the Cu3 cluster, providing both atomically precise experimental analogues of static surface species and emulating dynamic ligand behavior proposed for surfaces. Electronic structure calculations serve as a predictor of hydricity, which was likewise benchmarked experimentally via both protonolysis and hydride abstraction reactions. Increased hydride number (and commensurately lower cluster charge) results in more hydridic complexes, with a thermodynamic hydricity range spanning >30 kcal/mol. These thermochemical studies serve as an accurate predictor of CO2 reactivity. Together, this Cu3Hx series exhibits the structure/reactivity relationships proposed for catalytically active copper surfaces, validating the application of carefully designed molecular clusters toward elucidating mechanisms in surface science.

The superiority of non-frustrated over frustrated Lewis pairs in the copper-catalyzed hydrogenation of CO2 to formate

Bertrand and we had found that typical frustrated Lewis pairs (FLPs), well-known to activate H2, were less efficient than non-frustrated Lewis Pairs (n-FLPs) for the hydrogenation of CO2 to formate in the presence of a copper hydride. Herein, through experimental and computational studies, a possible mechanism was proposed. We show that moderately bulky bases, which formed n-FLPs with tris(pentafluorophenyl)borane (BCF), are also able to activate H2 and serve as catalyst for the hydrogenation of CO2 to formate. Though FLPs are super active for H2 activation, it prevents the formation of active Cu-H. Thus, FLPs were less efficient for the hydrogenation of CO2 to formate. We expect these results to inspire and act as a guiding principle toward the development of novel Lewis pair catalyzed reactions.