Organometallics最新文献

Complex OsH₄{κ¹-P,η²-GeH-[ⁱPr₂PCH(Me)CH₂GeEt₂H]}(PⁱPr₃) (1) breaks down formic acid into H₂ and CO₂. The decomposition is catalytic with complex 1 being the main metallic species detected spectroscopically during the process. The kinetic analysis of the catalysis reveals that the decomposition rate is first order in the catalyst and independent of the concentration of formic acid, with the calculated activation parameters being: ΔH^⧧ = 23 ± 2 kcal mol^–1, ΔS^⧧ = −1 ± 5 cal mol^–1 K^–1, and ²⁹⁸ΔG^⧧ = 23 ± 3 kcal mol^–1. Complex 1 also shows stoichiometric reactivity with benzoic and acetic acids. The reactions lead to OsH₂{κ²-O,O-[O₂CR]}{κ²-P,Ge-[ⁱPr₂PCH(Me)CH₂GeEt₂]}(PⁱPr₃) (R = Ph (9), Me (10)). On the basis of these findings and DFT calculations, the following mechanism for the decomposition is proposed: complex 1 releases one molecule of H₂ to produce an osmium(IV)-trihydride unsaturated intermediate, which promotes heterolytic activation of the O–H bond of formic acid. The metal fragment of the resulting osmium(IV)-(κ¹-O-formate)-saturated derivative slides along the formate group, following the O–C–H pathway. The displacement is assisted externally by a molecule of formic acid and generates an osmium(IV)-(κ¹-H-formate) species, which releases CO₂ to regenerate 1 and close a cycle. The dissociation of H₂ from the latter is the rate-determining step of catalysis.

According to the National Cancer Institute, breast cancer is a leading cause of death in women. The lack of progesterone and estrogen receptors in triple-negative breast cancer (TNBC) cells results in a lack of response to hormonal, monoclonal, or tyrosine kinase inhibitor therapies. Despite intensive drug discovery, there is still no approved targeted treatment for TNBC. The metalloid arsenic has been used in herbal medicines, antibiotics, and chemotherapeutic drugs for centuries. This paper demonstrates that a trivalent arsenic-containing, nonproteogenic amino acid, R-AST–OH (2-amino-4-(dihydroxyarsinoyl) butanoate), inhibits kidney-type glutaminase (KGA), the enzyme that controls glutamine metabolism and is correlated with tumor malignancy. Cell-based assays using the TNBC MDA-MB-231 and HCC1569 cell lines showed that R-AST–OH kills TNBC cells and is not cytotoxic to a control cell line. The results of in silico molecular docking predictions indicate that R-AST–OH binds to the glutamine binding site and forms a covalent bond with an active site cysteine residue. We hypothesize that R-AST–OH is a single warhead for KGA that irreversibly binds to KGA through the formation of an As–S bond. We propose that R-AST–OH is a promising lead compound for the design of new drugs for the treatment of TNBC.

The synthesis and characterization of a series of mono-, homo-, and heterobimetallic complexes involving iridium and rhodium centers have been achieved through the reaction of the proligand, 1-pyridyl-4-phenyl-1,2,3-triazole, and [M(Cp)*Cl₂]₂ (M = Ir, Rh). The ligand undergoes coordination of the N,N fragment and subsequent N-directed C–H activation at the 1,2,3-triazole and phenyl or pyridyl moieties. Alternatively, direct N-directed C–H activation can be achieved. The structures of the prepared complexes were determined using spectroscopic techniques and confirmed by X-ray crystallography. The electrochemical properties of the complexes show a differentiate redox behavior between Ir–Ir centers and a clear influence of the second metal in heterobimetallic complexes. This flexible approach could have potential applications in catalysis and other areas of chemistry.

The gold(I) N-heterocyclic carbene (NHC) complexes, containing a combination of 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene (iPr) and the corresponding 7-azaindole derivative (HL1–4), were prepared and characterized. The complexes of the composition of [Au(iPr)(Ln)], where n = 1–4 for 5-fluoro-7-azaindole (1), 5-bromo-7-azaindole (2), 3-chloro-7-azaindole (3), and 3-iodo-7-azaindole (4), were further evaluated for their in vitro anticancer and anti-inflammatory activities. The results showed that complexes (1–4) behave as considerably cytotoxic against human ovarian cancer cell line A2780 (with IC₅₀ ≈ 4–9 μM) and cisplatin-resistant cell line A2780R (with IC₅₀ ≈ 7–12 μM, except for 2 with IC₅₀ > 25 μM), providing significantly higher cytotoxicity than the anticancer drug cisplatin. Moreover, they also revealed a relatively good selectivity over normal cells (MRC-5), with selectivity index values of SI > 2.5. Complex 4 showed the ability to interact with l-cysteine and reduced glutathione at normal extracellular and intracellular levels, respectively. Complex 4 was further studied for its cellular effects in A2780 cells using flow cytometry. The ability of complexes (1–4) to influence the activity of pro-inflammatory transcription factor NF-κB and secretion of TNF-α were evaluated, showing that complex 4 reveals comparable effects as the inflammatory drug auranofin.

Isolable N-heterocyclic phosphenium (NHP) complexes of vanadium were prepared by cophotolysis of Na[V(CO)₆] and 2-bromo-1,3,2-diazaphospholenes. Single-crystal XRD studies revealed that the complexes exhibit trigonal planar coordination at phosphorus and short P–V distances indicative of phosphorus–metal double bonding. An exemplary reaction with Li[BEt₃H] proceeded via hydride transfer to the phosphorus atom to yield an anionic secondary phosphine complex, which resisted protonation by [Et₃NH]Cl and differed in this aspect from a previously reported manganese-based analogue. DFT calculations were carried out to analyze metal–ligand interactions in the NHP vanadium complexes and to rationalize the different behavior of the vanadium- and manganese-based species in H^–/H⁺-transfer reactions.

Hydrosilylation of double-decker silsesquioxanes is an efficient approach for preparing hybrid materials, especially polymeric materials. Karstedt’s catalyst, Pt(dvs), is widely used for this purpose due to its commercial availability, high yields, and good hydrosilylation selectivity. Despite this, vinylbenzenes have been shown to produce multiple hydrosilylated products. This study employs a method involving an iridium catalyst that was significantly more selective for the anti-Markovnikov hydrosilylation product with vinylbenzenes and bis-silane-capped double-decker silsesquioxanes. Obtaining higher purity of hydrosilylated products will allow for the development of the fundamental structure–property relationship of hybrid materials.

A dinucleating 1,8-naphthyridine ligand featuring fluorene-9,9-diyl-linked phosphino side arms (PNNP^Flu) was synthesized and used to obtain the cationic dicopper complexes 2, [(PNNP^Flu)Cu₂(μ-Ph)][NTf₂]; [NTf₂] = bis(trifluoromethane)sulfonimide, 6, [(PNNP^Flu)Cu₂(μ-CCPh)][NTf₂], and 3, [(PNNP^Flu)Cu₂(μ-O^tBu)][NTf₂]. Complex 3 reacted with diboranes to afford dicopper μ-boryl species (4, with μ-Bcat; cat = catecholate and 5, with μ-Bpin; pin = pinacolate) that are more reactive in C(sp)–H bond activations and toward activations of CO₂ and CS₂, compared to dicopper μ-boryl complexes supported by a 1,8-naphthyridine-based ligand with di(pyridyl) side arms. The solid-state structures and DFT analysis indicate that the higher reactivities of 4 and 5 relate to changes in the coordination sphere of copper, rather than to perturbations on the Cu–B bonding interactions. Addition of xylyl isocyanide (CNXyl) to 4 gave 7, [(PNNP^Flu)Cu₂(μ-Bcat)(CNXyl)][NTf₂], demonstrating that the lower coordination number at copper is chemically significant. Reactions of 4 and 5 with CO₂ yielded the corresponding dicopper borate complexes (8, [(PNNP^Flu)Cu₂(μ-OBcat)][NTf₂]; 9, [(PNNP^Flu)Cu₂(μ-OBpin)][NTf₂]), with 4 demonstrating catalytic reduction in the presence of excess diborane. Related reactions of 4 and 5 with CS₂ provided insertion products 10, {[(PNNP^Flu)Cu₂]₂[μ-S₂C(Bcat)₂]}[NTf₂]₂, and 11, [(PNNP^Flu)Cu₂(μ,κ²-S₂CBpin)][NTf₂], respectively. These products feature Cu–S–C–B linkages analogous to those of proposed CO₂ insertion intermediate.

The synthesis and characterization of five-coordinate rhodium(III) and iridium(III) complexes of the form [M(PNP-Np)(biph)][BAr^F₄] are described, where PNP-Np is the neopentyl-substituted pincer ligand 2,6-(Np₂PCH₂)₂C₅H₃N (Np = CH₂tBu), biph = 2,2′-biphenyl, and Ar^F = 3,5-(CF₃)₂C₆H₃. These complexes are notable for the adoption of δ-agostic interactions in the solid state, as evidenced by X-ray crystallography (50–150 K) and ATR-IR spectroscopy, but are structurally dynamic in solution, exhibiting pseudorotation of the biph ligand on the ¹H NMR time scale (185–308 K). The strength of the agostic interactions is discussed with reference to the known tert-butyl-substituted analogues [M(PNP-tBu)(biph)][BAr^F₄], probed by reaction with carbon monoxide, and quantified computationally through NBO analysis, from which the conclusion is that 3-center–2-electron bonding increases in the order M = Ir > Rh (cf. 1.5× greater perturbation energy) and pincer ligand = PNP-Np > PNP-tBu (cf. 3.3× greater perturbation energy).