Organometallics最新文献

Pincer complexes efficiently catalyze reactions to generate medicinally important scaffolds using either acceptorless dehydrogenative coupling (ADC) or borrowing hydrogen process (BHP)-based catalytic reactions. A few pincer complexes have been reported to catalyze both pathways. Recently, our group reported the generation of the NNN-Pd(II) pincer complex and established its catalytic efficiency in ADC and BHP in two different reactions. The current work discusses the application of the NNN-Pd(II) catalyst for ADC and BHP on fluorene. Control experiments and quantum chemical studies were conducted to examine the mechanistic pathway of the reaction. Utilization of intermediate II-B toward H₂ gas elimination or the reduction of alkenylated fluorene determines the control of selectivity in the formation of alkylated vs. alkenylated products, depending upon the amount of alcohol and base.

This report describes the synthesis and reactivity of the heteroleptic phosphinimide/phosphinimine Cr(II) complex HL′CrAdHMDS, which was obtained by incomplete protonolysis of Cr(HMDS)2(THF)2 in the presence of the bisphosphinimine pro-ligand H2L′Ad. Addition of common ligands such as N-heterocyclic carbenes and isocyanides displaces the remaining HMDS ligand concomitant with complete deprotonation of the phosphinimine pro-ligand furnishing three- and four-coordinated complexes, respectively. The resulting tetrahedral chromium(II) bis(isocyanide) species was found to adopt an unusual S = 1 spin state at room temperature. Under certain reaction conditions, one coordinated isocyanide ligand was found to insert into a chromium-phosphinimide bond. The described compounds are characterized by single-crystal X-ray diffraction and solution-phase spectroscopy, and the mechanism for isocyanide insertion was investigated by DFT calculations.

Two carborane-functionalized thiocarbohydrazone derivatives, TCH-m-CB and TCH-p-CB, were synthesized and well-characterized. The anticancer potential of these compounds was evaluated in vitro against the MCF-7 human breast cancer cell line and NIH/3T3 mouse embryo fibroblast cell line. The cytotoxicity study shows that the meta-carborane derivative, TCH-m-CB, shows higher cytotoxicity toward cancer cells with an IC₅₀ value of 36.96 μM. The caspase-3 activity assays confirmed that both compounds induce cell death through apoptosis. The computational DFT studies indicated a higher HOMO–LUMO energy gap for TCH-m-CB (3.870 eV) compared to TCH-p-CB (2.811 eV), indicating a higher stability of the meta-carborane derivative, TCH-m-CB, in the ground state. The molecular docking study shows that the thiocarbohydrazone derivatives of carboranes exhibit stronger binding affinities to key cancer-related protein targets (Erα, Topo IIα, and PARP-1) than the reference drug, doxorubicin. The in silico analysis of the ADMET properties of thiocarbohydrazone derivatives of carboranes also exhibits highly promising drug-like properties as compared to the reference drug doxorubicin. Overall, the results indicate that the carborane-functionalized thiocarbohydrazone derivatives have the potential to be effective anticancer agents.

The reaction between (C₅Me₅)₂Y(μ–Ph)₂BPh₂ and NaC≡CH was explored to examine the reactivity of an intermediate like “(C₅Me₅)₂Y(C≡CH).” One of the products identified from the reaction mixture is a bimetallic Y(III) complex that contains a rare example of a planar and dianionic bridging butatrienylidene ligand, namely (C₅Me₅)₂Y(μ-η³:η¹-CCCCH₂)Y(C₅Me₅)₂. The bridging butatrienylidene ligand is presumably formed from the C–C coupling of two (C≡CH)^1– moieties that also involve the migration of a hydrogen atom to form the terminal methylidene group. Density functional theory (DFT) studies were conducted to probe the electronic structure of the unsaturated (C₄H₂)^2– dianion.

The development of main-group compounds for the activation of inert bonds is crucial for transition-metal-free catalysis. Herein, we report the synthesis and characterization of a carboranyl silylene–borane (1). The cooperative interaction between silylene and borane moieties enables 1 to activate pyridine, 4-(trifluoromethyl)pyridine and 4-dimethylaminopyridine, leading to the formation of azasilepins. These results illustrate a novel main-group cooperative platform for bond activation, underscoring its potential to advance molecular transformations.

Herein, we report the synthesis and characterization of an N-heterocyclic silylene-stabilized digermanium radical cation (3) via the single-electron oxidation of a digermanium(0) compound (2). Characterization data and DFT calculations show that compound 3 possesses a Ge═Ge double bond, and the unpaired electron is primarily localized at the p-orbitals of the two Ge centers.

Complexes of a new PNONP ligand that combines a central alkoxide with two diarylamido and two phosphine donors have been prepared. The PNONP functions as a pentadentate ligand in an octahedral Re complex but forms bimetallic complexes with two square-planar Ni or Pd centers. The Ni or Pd centers can be viewed as each supported by a PNO pincer, with the alkoxide O bridging the two metals.

The ligand exchange mechanisms of titanocene complexes were investigated by using density functional theory (DFT) to elucidate the reactivity trends of halogenation and deprotection reactions involving dithiolate-substituted species. Specifically, the transformations of titanocene dithiolate into dichloride and difluoride complexes via HCl, HF, and XeF₂ were examined. The study reveals that these processes follow an associative interchange (I_a) mechanism, with significant differences in activation barriers and intermediates depending on the halogen source. While HCl-mediated substitution proceeds through defined multistep pathways with moderate activation energies, HF requires higher activation energy and slower reaction rates. In contrast, XeF₂ enables a radical-mediated pathway characterized by near-barrierless energy profiles, explaining its experimentally observed rapid fluorination. Additionally, the reverse reaction, formation of the dithiolate complex from titanocene dichloride, was shown to be thermodynamically unfavorable without base-mediated deprotonation. This comprehensive analysis underscores the role of ligand electronics and the unique reactivity of XeF₂, offering mechanistic insights that may aid future applications of titanocenes in positron emission tomography (PET) imaging and medicinal chemistry.

In this work, we interrogate the reactivity of pentaphenylborole with 4,4′-bis(dimethylamino)benzophenone (Michler’s ketone) and its heavier congener, bis(dimethylamino)thiobenzophenone (Michler’s thioketone). The ketone inserts the CO unit to generate an unsaturated BOC₅ heterocycle while the thioketone coordinates to the boron center but the adduct thermally isomerizes via migration of a C-Ph unit and insertion of the sulfur atom to furnish a BSC₃ boracycle with a pendent alkene.

The actinide elements and, in particular, the transuranic elements are some of the least studied elements on the periodic table. As a consequence, there is not currently a consensus on the impact of covalency in actinide complexes. Dithiolene/dithiolate ligands provided a revolution in understanding the bonding in transition metals through the geometric differences the ligands exhibit when interacting with electron-deficient or -abundant metal centers. To test if dithiolene/dithiolate ligands can be utilized to provide an analogous understanding of transuranic element bonding, density functional theory calculations have been performed on U, Np, and Pu complexes of the formula Cp₂AnS₂C₂H₂. These calculations show that the dithiolate maintains its non-innocent redox-active nature when bonding with actinides. In stark contrast with the transition metals, the direction of electron donation is reversed; in the actinide series, the direction of electron flow in high-fold cases is from the metal center to the ligand. This suggests that the communication is between the π* system of the ligand interacting with the f orbitals of the metal center.