A dinuclear nickel peroxycarbonate complex: CO addition promotes HO release.

Nickel coordination compounds featuring Ni-O bonds are key structural motifs in both bioinorganic and synthetic chemistries. They serve as precursors for organic substrate oxidation and are commonly invoked intermediates in water oxidation and oxygen reduction schemes. Herein, we disclose a series of well-defined dinuclear nickel complexes that, upon treatment with CO and HO, afford the first nickel-bound peroxycarbonate.

Mechanistic insights into radical formation and functionalization in copper/-fluorobenzenesulfonimide radical-relay reactions.

Copper-catalysed radical-relay reactions that employ -fluorobenzenesulfonimide (NFSI) as the oxidant have emerged as highly effective methods for C(sp)-H functionalization. Herein, computational studies are paired with experimental data to investigate a series of key mechanistic features of these reactions, with a focus on issues related to site-selectivity, enantioselectivity, and C-H substrate scope. (1) The full reaction energetics of enantioselective benzylic C-H cyanation are probed, and an adduct between Cu and the -sulfonimidyl radical (˙NSI) is implicated as the species that promotes hydrogen-atom transfer (HAT) from the C-H substrate.

Accessing Ta/Cu Architectures via Metal-Metal Salt Metatheses: Heterobimetallic C-H Bond Activation Affords μ-Hydrides.

We employ a metal-metal salt metathesis strategy to access low-valent tantalum-copper heterometallic architectures (Ta-μ -H -Cu and Ta-μ -H -Cu ) that emulate structural elements proposed for surface alloyed nanomaterials. Whereas cluster assembly with carbonylmetalates is well precedented, the use of the corresponding polyarene transition metal anions is underexplored, despite recognition of these highly reactive fragments as storable sources of atomic M . Our application of this strategy provides structurally unique early-late bimetallic species.

The NADH recycling enzymes TsaC and TsaD regenerate reducing equivalents for Rieske oxygenase chemistry.

Many microorganisms use both biological and nonbiological molecules as sources of carbon and energy. This resourcefulness means that some microorganisms have mechanisms to assimilate pollutants found in the environment. One such organism is Comamonas testosteroni, which metabolizes 4-methylbenzenesulfonate and 4-methylbenzoate using the TsaMBCD pathway.

Synthesis, Structural Characterization, and CO 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 (CO), an early mechanistic branching point in the CO reduction reaction. Herein, we report the synthesis, characterization, and reactivity of tricopper compounds supported by a facially biased, chelating tris(carbene) ligand scaffold.

Molybdenum-Mediated Coupling of Carbon Monoxide to a C Product on a Single Metal Site.

The synthesis and characterization of a series of naphthalenediyl-diphosphine molybdenum complexes are reported. A novel dicarbonyl-Mo complex () converts to a bis(siloxy)acetylene complex () upon reduction and treatment with a silyl electrophile, MeSiCl. This process shows exclusive C-C coupling distinct from the previously reported phenylene-linked analogue that undergoes C-O cleavage.

Cu-Catalyzed Site-Selective Benzylic Chlorination Enabling Net C-H Coupling with Oxidatively Sensitive Nucleophiles.

Site-selective chlorination of benzylic C-H bonds is achieved using a CuCl/bis(oxazoline) catalyst with -fluorobenzenesulfonimide as the oxidant and KCl as a chloride source. This method exhibits higher benzylic selectivity, relative to established chlorination protocols, and is compatible with diverse alkyl arenes. Sequential benzylic C-H chlorination/nucleophilic substitution affords C-O, C-S, and C-N coupling products with oxidatively sensitive coupling partners.

Terminal, Open-Shell Mo Carbide and Carbyne Complexes: Spin Delocalization and Ligand Noninnocence.

Open-shell compounds bearing metal-carbon triple bonds, such as carbides and carbynes, are of significant interest as plausible intermediates in the reductive catenation of C oxygenates. Despite the abundance of closed-shell carbynes reported, open-shell variants are very limited, and an open-shell carbide has yet to be reported. Herein, we report the synthesis of the first terminal, open-shell carbide complexes, and ( = P2Mo(≡C:)(CO), P2 = a terphenyl diphosphine ligand), which differ by two redox states, as well as a series of related open-shell carbyne complexes.

Copper-Catalyzed C-H Fluorination/Functionalization Sequence Enabling Benzylic C-H Cross Coupling with Diverse Nucleophiles.

Site-selective transformation of benzylic C-H bonds into diverse functional groups is achieved via Cu-catalyzed C-H fluorination with -fluorobenzenesulfonimide (NFSI), followed by substitution of the resulting fluoride with various nucleophiles. The benzyl fluorides generated in these reactions are reactive electrophiles in the presence of hydrogen-bond donors or Lewis acids, allowing them to be used without isolation in C-O, C-N, and C-C coupling reactions.

Copper-Catalyzed Functionalization of Benzylic C-H Bonds with -Fluorobenzenesulfonimide: Switch from C-N to C-F Bond Formation Promoted by a Redox Buffer and Brønsted Base.

A copper catalyst in combination with -fluorobenzenesulfonimide (NFSI) has been reported to functionalize benzylic C-H bonds to the corresponding benzylic sulfonimides via C-N coupling. Here, we reported a closely related Cu-catalyzed method with NFSI that instead leads to C-F coupling. This switch in selectivity arises from changes to the reaction conditions (Cu/ligand ratio, temperature, addition of base) and further benefits from inclusion of MeB(OH) in the reaction.

Copper-catalysed benzylic C-H coupling with alcohols via radical relay enabled by redox buffering.

Cross-coupling reactions enable rapid, convergent synthesis of diverse molecules and provide the foundation for modern chemical synthesis. The most widely used methods employ sp-hybridized coupling partners, such as aryl halides or related pre-functionalized substrates. Here, we demonstrate copper-catalysed oxidative cross coupling of benzylic C-H bonds with alcohols to afford benzyl ethers, enabled by a redox-buffering strategy that maintains the activity of the copper catalyst throughout the reaction.

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone.

The mechanism originally proposed by Fischer and Tropsch for carbon monoxide (CO) hydrogenative catenation involves C-C coupling from a carbide-derived surface methylidene. A single molecular system capable of capturing these complex chemical steps is hitherto unknown. Herein, we demonstrate the sequential addition of proton and hydride to a terminal Mo carbide derived from CO.

Molecular Mimics of Heterogeneous Metal Phosphides: Thermochemistry, Hydride-Proton Isomerism, and HER Reactivity.

A new series of low-valent dinuclear molybdenum complexes bearing phosphido or phosphinidene bridging ligands was synthesized as a structural model of heterogeneous metal phosphide catalysts. Addition of acid to a monocationic Mo -μ-P complex results in phosphide protonation, affording a dicationic Mo -μ-PH species. Alternatively, reaction of an isoelectronic Mo -μ-P precursor with LiBEt H gives a Mo H-μ-P complex.

Lewis Acid Enhancement of Proton Induced CO Cleavage: Bond Weakening and Ligand Residence Time Effects.

Though Lewis acids (LAs) have been shown to have profound effects on carbon dioxide (CO) reduction catalysis, the underlying cause of the improved reactivity remains unclear. Herein, we report a well-defined molecular system for probing the role of LA additives in the reduction of CO to carbon monoxide (CO) and water. Mo(0) CO complex (2) forms adducts with a series of LAs, demonstrating CO activation that correlates linearly with the strength of the LA.

A Low-Valent Molybdenum Nitride Complex: Reduction Promotes Carbonylation Chemistry.

Toward nitrogen functionalization, reactive terminal transition metal nitrides with high d-electron counts are of interest. A series of terminal Mo nitride complexes were prepared within the context of exploring nitride/carbonyl coupling to cyanate. Reduction affords the first Mo nitrido complex, an early metal nitride with four valence d-electrons.

Mild electrochemical synthesis of metal phosphides with dibenzo-7-phosphanorbornadiene derivatives: mechanistic insights and application to proton reduction in water.

Transition metal phosphide films were synthesized using a mild electrochemical method. Dibenzo-7-phosphanorbornadiene derivatives (XPA) are introduced as versatile precursors to amorphous metal phosphide electrocatalysts for proton reduction in acidic water. Homogeneous model reactions reveal distinct reactivity between XPA and nickel in different oxidation states, with Ni(0) resulting in NiP formation.

Terminal Molybdenum Phosphides with d Electrons: Radical Character Promotes Coupling Chemistry.

A terminal Mo phosphide was prepared through the group transfer of both P and Cl atoms from chloro-substituted dibenzo-7λ -phosphanorbornadiene. This compound represents the first structurally characterized terminal transition-metal phosphide with valence d electrons. In the tetragonal ligand field, these electrons populate an orbital of d parentage, an electronic configuration that accommodates both metal d electrons and a formal M≡P triple bond.

Mechanism of Molybdenum-Mediated Carbon Monoxide Deoxygenation and Coupling: Mono- and Dicarbyne Complexes Precede C-O Bond Cleavage and C-C Bond Formation.

Deoxygenative coupling of CO to value-added C products is challenging and mechanistically poorly understood. Herein, we report a mechanistic investigation into the reductive coupling of CO, which provides new fundamental insights into a multielectron bond-breaking and bond-making transformation. In our studies, the formation of a bis(siloxycarbyne) complex precedes C-O bond cleavage.

Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site.

Carbon dioxide is the ultimate source of the fossil fuels that are both central to modern life and problematic: their use increases atmospheric levels of greenhouse gases, and their availability is geopolitically constrained. Using carbon dioxide as a feedstock to produce synthetic fuels might, in principle, alleviate these concerns. Although many homogeneous and heterogeneous catalysts convert carbon dioxide to carbon monoxide, further deoxygenative coupling of carbon monoxide to generate useful multicarbon products is challenging.

Molybdenum catalyzed ammonia borane dehydrogenation: oxidation state specific mechanisms.

Though numerous catalysts for the dehydrogenation of ammonia borane (AB) are known, those that release >2 equiv of H2 are uncommon. Herein, we report the synthesis of Mo complexes supported by a para-terphenyl diphosphine ligand, 1, displaying metal-arene interactions. Both a Mo(0) N2 complex, 5, and a Mo(II) bis(acetonitrile) complex, 4, exhibit high levels of AB dehydrogenation, releasing over 2.