Organometallics最新文献

The synthesis of a new Cp*Co(III) complex bearing a bis-carbene ligand (1,1′-dimethyl-4,4′-bi-1,2,4-triazol-5,5′-ylidene, bitz) is reported. The synthetic approach utilizes a Co(I) precursor and a bis-triazolium salt without the need for a base or an external oxidant. The electrochemical properties of the complex have been studied.

This paper reports on a synthetic approach to 1,2-disubstituted carboxonium derivatives [1,2-B₁₂H₁₀O₂CR]⁻ that combines acylation and (diacetoxyiodo)benzene-promoted cyclization reactions. The formation pathway of the carboxonium ring fused to the closo-dodecaborate was examined using DFT calculation and it was found that the reaction includes two main transition states corresponding to the deprotonation-iodination of the cluster and intramolecular cyclization. It was established that the nature of the R-substituent significantly affects the stability of the carboxonium ring to opening processes initiated by water and alcohols. It was also demonstrated that, depending on the nucleophilicity of the reagent, both mixed derivatives with hydroxy and acyloxy groups and dihydroxy derivatives can be obtained.

We report the synthesis and characterization of a new p-dimethylamino-substituted thiapyridinophane ligand (^pNMe2NCHS2) and its palladium complexes. The electron-rich dimethylamino groups engender the palladium compounds with several unusual properties compared to the parent unsubstituted NCHS2 ligand. A facile room-temperature C(sp²)–H activation of the ^pNMe2NCHS2 ligand was observed, which is facilitated by the p-dimethylamino group acting as an internal base. NMR spectroscopic and mechanistic studies were conducted to gain insight into the possible mechanism of the C–H activation process.

The reduction of carbon dioxide mediated by N-phosphinoamidinato silylenes was described. The reaction of an N-phosphinoamidinato chlorosilylene 1 with CO₂ afforded carbon monoxide and a dioxo-bridged siloxane 2. Compound 1 was then reduced with KC₈ to form base-stabilized disilyne 5, where the interconnected silylene centers reduce CO₂ to form CO and carbonate(dioxo)-bridged siloxane derivative 6. In the CO₂ reduction, the N-phosphinoamidinate ligand interchanges between N,N′- and N,P-chelate, showing the hemilabile character depending on the oxidation state of the silicon center.

The use of pyrylium and related catalysts for sp³ C–O bond reduction is reported. Studies on a cationic, divalent Ge complex ([Cp*Ge⁺][B(C₆F₅)₄^–]) used for deoxygenation reactions reveal that O₂ is required for the oxidation of the complex into an active pyrylium catalyst. Reactivity screens show pyrylium, flavylium, and xanthylium catalysts are active, leading to a diverse, bench-stable, and highly tunable catalyst library.

Treatment of a heterometallic uranium–gold complex with KC₈ facilitates the six-electron reduction of N₂, yielding a multimetallic U₄Au₄N₂ complex featuring two μ₃-bridging nitrido ligands. This work represents a rare example of N₂ cleavage promoted by a uranium–transition metal species and highlights the potential of heterometallic cooperativity for small-molecule activation.

Interaction of {Cryptand(K⁺)}(C₆₀^•–) with CpCo(CO)₂ yields the air-sensitive crystalline salt {Cryptand(K⁺)}{CpCo(CO)-η²-C₆₀^•–} (1), in which C₆₀^•– replaces carbonyl group in CpCo(CO)₂. Two Co–C bonds of 2.028(9) and 2.057(8)Å are formed. The magnetic moment of 1 is 1.72 μ_B, indicating a doublet S = 1/2 spin state of {CpCo(CO)-η²-C₆₀^•–} at 300 K. The compound shows a broad EPR signal at g = 2.0000 with a line width of 3.93 mT (295 K), characteristic of C₆₀^•–, confirming spin and electron density localization on the fullerene cage. This is the first coordination complex of a transition metal with C₆₀^•–. Below 220 K, {CpCo(CO)-η²-C₆₀^•–} dimerizes to form diamagnetic singly bonded {CpCo(CO)-η²-C₆₀^–}₂ dimers. Carbon atoms of the [6,6,5] junctions form an intercage single C–C bond of 1.619(18)Å. Dimerization elongates the Co–C bonds to 2.098(13) and 2.106(13)Å. Approximately 20% of S = 1/2 spins remain after dimerization indicating partial preservation of the paramagnetic monomeric phase. Coordination of C₆₀^•– to CpCoCO becomes asymmetric in this phase, with shorter and longer Co–C bonds of 2.012(14) and 2.262(14) Å, converting the η²-type to η -type coordination. Dimerization is partially suppressed owing to the formation of densely packed C₆₀^•– chains, where radical anions align hexagon-over-hexagon in parallel with close interplanar distances.

In this work, we report the synthesis of a Nacnac^Dipp-ligated zinc-Bpin species, compound 3, which was characterized by single-crystal X-ray analysis, NMR, and HRMS spectra. Similar to previously reported zinc-Bcat species, it can also act as a Bpin^– nucleophile toward MeI, yielding MeBpin. Furthermore, it can react with phenyl azide to produce an imide species, which can be interpreted as the result of phenylnitrene insertion into the Zn–B bond.

An efficient approach for the p-block selenium-catalyzed migratory Wacker oxidation of tetrasubstituted alkenes is developed. Under mild conditions, cyclic tetrasubstituted alkenes bearing aryl and geminal dimethyl groups can undergo six-to-seven or five-to-six ring expansion to give a series of ketones bearing a gem-dimethyl group via oxidative aryl migration. The method could be employed for the Wacker oxidation of acyclic tetrasubstituted alkenes as well. The obtained gem-dimethyl ketones are appealing in medicinal chemistry. It is believed that a selenenylation–deselenenylation followed by a semipinacol rearrangement process is involved in the reactions. This work provides a new strategy for the synthesis of gem-dimethyl molecules, and is complementary to the fields of p-block main group element catalysis and Wacker oxidation.

The unexpected formation of a bifluorene-bridged phenoxy-imine (FI) Ti(IV) complex, generated from a fluorene-functionalized phenoxy-imine ligand via in situ C–C bond formation, was established through comprehensive characterization including single-crystal X-ray analysis. The bifluorene-bridged Ti(IV) complex exhibited a selective trans-dichloride geometry, in contrast to the commonly observed cis-arrangement, offering expansion to the structural landscape of Ti(IV) FI type of olefin polymerization catalysts.