Organometallics最新文献

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.

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.

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.

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.

In the coordination chemistry of heavier tetrylenes (:ER₂, where E = Si, Ge, Sn, Pb), chelating P,N-donor ligands occupy a privileged position, though phosphinoamido ligands, [R₂P–NR′]⁻, have been barely investigated. Herein, we report the synthesis and structural characterization of such complexes, whose structures drastically differ depending on the group 9 metal precursor used. Strained four-membered {P–N–Ge–M} metallacycles (M = Rh, Ir) are produced from the reaction of phosphinoamido germylenes with [MCl₂Cp*]₂ precursors (Cp* = η⁵-C₅Me₅). At variance, [MCl(COD)]₂ dimers are not broken apart; instead, they afford bimetallic species featuring bridging phosphinoamido–germyl and chloride ligands between the two metals. All new compounds were isolated on a preparative scale and spectroscopically characterized and their structures confirmed by X-ray diffraction. Computational studies support the σ-donor character of the Ge–M interaction and the absence of significant π-backbonding.

The strong fluoroaryl borane Lewis acid B(C₆F₅)₃ (FAB) is known to catalyze the Piers–Rubinsztajn (PR) reaction (coupling of silyl hydrides with alkoxysilanes), among other related reactions relevant to the formation of commercially useful siloxane intermediates or cured siloxane networks. However, the catalyst induces undesired self-cure of Si–H-containing siloxanes, limiting its industrial applicability in polymer systems. Despite the versatility of this catalyst, there has been relatively little focus on optimizing the performance of the catalyst through structural modifications. In this work, we show that simple changes, either steric or electronic, to the structure of the Lewis acid help modulate the catalytic activity of such Lewis acids, eliminating the undesirable self-cure and improving their usefulness in reactions of industrial interest.

Protonolysis of the half-sandwich complex [Cp*Sc(AlMe₄)Cl]₂ (Cp* = C₅Me₅) with [Et₃NH][BPh₄] leads to deprotonation and rearrangement of the [BPh₄]⁻ anion to form the half-sandwich scandium boracycle complex Cp*Sc(η⁶-C₂₄H₁₉B). The new dianionic fragment [C₂₄H₁₉B]^2– results from a B–C and C–C bond breaking/formation sequence where the boron atom has been inserted into a phenyl ring, and one carbon atom is now sp³ hybridized. Complex Cp*Sc(η⁶-C₂₄H₁₉B) was analyzed by SC-XRD, ¹H, ¹³C{¹H}, ¹¹B{¹H}, and ⁴⁵Sc{¹H} NMR, and elemental analysis. The high reactivity of transient the [Cp*Sc(Me)Cl] species is further tracked by the structural snapshot of a scandium 1,2,3-benztriyne complex, resulting from the reaction of partly methylated Cp’Sc(AlMe₄)(Me/Cl) (Cp’ = C₅Me₄SiMe₃) with [Et₃NH][BPh₄]. Both reactions illustrate new activations of the [BPh₄]⁻ anion by organo-rare-earth-metal complexes.