ACS Organic & Inorganic Au最新文献

Desulfurization of organosulfur substrates is highly important due to its relation with the industrial hydrodesulfurization (HDS) process of fossil fuels, which helps to eliminate the sulfur-containing impurities such as thiols, sulfide, thiophenes, etc. from crude oil for the production of easily processed and more cleanly combusted fuel with very low sulfur content. While the HDS process involves a hydrogenolysis reaction under a high pressure of hydrogen gas at high temperature, the hydrolysis of C–S bonds of organosulfur substrates at ambient conditions may very well be considered as a potential alternative for model desulfurization reactions. However, unlike the availability of an appreciable number of reports on base, acid, and metal ion mediated hydrolysis of thioesters in the literature, reports on the hydrolysis of more difficult substrates such as thiolates, sulfides, and other organosulfur substrates remained unavailable until 2017. The very recent discovery of a transition metal mediated hydrolysis reaction of C–S bonds at ambient conditions, however, has rapidly filled in this gap within the past few years. Development of this new stoichiometric reaction allowed the desulfurization of a large number of organosulfur substrates, including aliphatic and aromatic thiols, thiocarboxylic acids, sulfides, disulfides, thiophenes, and dibenzothiophene, at ambient conditions and was subsequently converted to a catalytic process for the hydrolysis of thiols. A brief overview of this new reaction strategy, a proposed reaction mechanism, a critical analysis of the efficiency, and future prospects are presented.

Heterotrimetallic complexes with (N₂S₂)M metallodithiolates, M = Ni²⁺, [Fe(NO)]²⁺, and [Co(NO)]²⁺, as bidentate chelating ligands to a central trans-Cr(NO)(MeCN) unit were characterized as the first members of a new class, NiCrNi, FeCrFe, CoCrCo. The complexes exhibit a cisoid structural topology, ascribed to the stereoactivity of the available lone pair(s) on the sulfur donors, resulting in a dispersed, electropositive pocket from the N/N and N/S hydrocarbon linkers wherein the Cr-NO site is housed. Computational studies explored alternative isomers (transoid and inverted cisoid) that suggest a combination of electronic and steric effects govern the geometrical selectivity. Electrostatic potential maps readily display the dominant electronegative potential from the sulfurs which force the NO to the electropositive pocket. The available S lone pairs work in synergy with the π-withdrawing ability of NO to lift Cr out of the S₄ plane toward the NO and stabilize the geometry. The metallodithiolate ligands bound to Cr(NO) thus find structural consistency across the three congeners. Although the dinitrosyl [(bme-dach)Co(NO)-Mo(NO)(MeCN)-(bme-dach)Co(MeCN)][PF₆]₂ (CoMoCo′) analogue displays chemical noninnocence and a partial Mo–Co bond toward (N₂S₂)Co′(NCCH₃) in an “asymmetric butterfly” topology [Guerrero-Almaraz, P. Inorg. Chem. 2021, 60(2121), 15975–15979], the stability of the {Cr(NO)}⁵ unit prohibits such bond rearrangement. Magnetism and EPR studies illustrate spin coupling across the sulfur thiolate sulfur bridges.

Although stereochemical control of carbon centers is a well-established technique in modern synthetic chemistry, that of tetrahedral metal complexes with a stereogenic metal center remains difficult due to the dynamic nature of their coordination bonds. Here we report the synthesis of a tetrahedral d⁸ high-spin chiral-at-nickel(II) complex composed exclusively of achiral ligands and the supramolecular control of its temperature-dependent spontaneous resolution in crystals. Under certain conditions, complex molecules with the same absolute configuration of the nickel(II) center grow into conglomerate crystals with a helically arranged structure due to intermolecular hydrogen bonding. This process is highly spontaneous, does not require any chiral sources, and is closely related to the origin of homochirality in biological systems. The obtained enantiopure nickel(II) complex will be a new type of redox-active chiral source for asymmetric synthetic chemistry.

This Account highlights the recent contributions made by our laboratory in the development of novel strategies to synthesize fluorinated amines. These strategies allow the practitioner to efficiently access carbamoyl fluorides, thiocarbamoyl fluorides as well as trifluoromethylamines using CO₂ or CS₂ as benign C1 sources. In addition, a novel N(SCF₃)CF₃ moiety was synthesized. Noteworthy, we demonstrated that this reagent could also be used in radical- or electrophilic-based trifluoromethylthiolation reactions.

A catalytic chemical upcycling methodology for polyesters has been developed. Commodity polyesters, such as polyethylene terephthalate (PET), are depolymerized with morpholine by using a Cp*TiCl₃ catalyst under ambient pressure without any additives, which provides morpholine amides exclusively. The method can also apply to other polyesters, polybutylene terephthalate (PBT), polyethylene adipate (PEA), polybutylene adipate (PBA), and polybutylene succinate (PBS), as well as an actual PET waste of a 50 g postconsumer beverage bottle. The product, morpholine amide, is a versatile building block in organic chemistry, and the synthetic utility has thus been demonstrated by further transformations, such as hydrolysis, selective reductive conversions, and Grignard reaction.

The selective reduction of carbon dioxide remains a significant challenge due to the complex multielectron/proton transfer process, which results in a high kinetic barrier and the production of diverse products. Inspired by the electrostatic and H-bonding interactions observed in the second sphere of the [NiFe]-CODH enzyme, researchers have extensively explored these interactions to regulate proton transfer, stabilize intermediates, and ultimately improve the performance of catalytic CO₂ reduction. In this work, a series of cobalt(II) tetraphenylporphyrins with varying numbers of redox-active nitro groups were synthesized and evaluated as CO₂ reduction electrocatalysts. Analyses of the redox properties of these complexes revealed a consistent relationship between the number of nitro groups and the corresponding accepted electron number of the ligand at −1.59 V vs. Fc^+/0. Among the catalysts tested, TNPPCo with four nitro groups exhibited the most efficient catalytic activity with a turnover frequency of 4.9 × 10⁴ s^–1 and a catalytic onset potential 820 mV more positive than that of the parent TPPCo. Furthermore, the turnover frequencies of the catalysts increased with a higher number of nitro groups. These results demonstrate the promising design strategy of incorporating multielectron redox-active ligands into CO₂ reduction catalysts to enhance catalytic performance.

We identify the factors that rule the selectivity in single-cleavage skeletal rearrangements promoted by gold(I) catalysts. We find that stereoconvergence is enabled by a rotational equilibrium when electron-rich substituents are used. The anomalous Z-selective skeletal rearrangement is found to be due to electronic factors, whereas endo-selectivity depends on both steric and electronic factors.

A tetrapyridyl ligand with a bending anthraquinodimethane linker has been synthesized, and its complexation with coinage metals has been examined. The treatment of the ligand with Ag(I) and Au(I) cations afforded binuclear complexes, wherein the two metal centers were in close proximity to the inside space of the ligand. X-ray analyses corroborated with theoretical calculations indicated that the ligand has reasonable flexibility toward a bending deformation of the linker moiety to provide a ligand pocket suitable for the proximal binuclear complexes, even though such deformations accompany a non-negligible amount of energetic cost. On the other hand, treatment with 2 equiv of Cu(I) salt afforded a binuclear complex, in which both copper atoms were coordinated at the periphery of the ligand.

A Pd-catalyzed 3,4-regioselective cyclopropanation of 2-substituted 1,3-dienes by decomposition of diazo esters is reported. The vinylcyclopropanes generated are isolated in practical chemical yields with high levels of regioselectivity but low diastereoselectivity. The system operates under mild reaction conditions, is scalable, and tolerates various sensitive functional groups. A series of original postcatalytic derivatizations is presented to highlight the synthetic potential of the catalytic method.

We herein report a novel Mn-SNS-based catalyst, which is capable of performing indirect hydrogenation of CO₂ to methanol via formylation. In this domain of CO₂ hydrogenation, pincer ligands have shown a clear predominance. Our catalyst is based on the SNS-type tridentate ligand, which is quite stable and cheap as compared to the pincer type ligands. The catalyst can also be recycled effectively after the formylation reaction without any significant change in efficiency. Various amines including both primary and secondary amines worked well under the protocol to provide the desired formylated product in good yields. The formed formylated amines can also be reduced further at higher pressures of hydrogen. As a whole, we have developed a protocol that involves indirect CO₂ hydrogenation to methanol that proceeds via formylation of amines.