Search Results (76)

In this work we revisit a vast amount of existing data on physical properties of Ti-Zr-Nb-(Cu,Ni,Co) glassy alloys over a broad range of concentrations (from the high-entropy range to that of conventional Cu-, Ni- or Co-rich alloys). By using our new approach based on the total content of late transition metal(s), we derive a number of physical parameters of a hypothetical amorphous TiZrNb alloy: lattice parameter $a=(3.42\pm 0.02)$ Å, Sommerfeld coefficient $\gamma =6.2\mathrm{mJ/mol}$${\mathrm{K}}^2$, density of states at $N\left(E_F\right)=2.6{\left(\mathrm{at}\mathrm{eV}\right)}^{-1}$, magnetic susceptibility $(2.00\pm 0.05)$mJ/${\mathrm{T}}^2$mol, superconducting transition temperature $T_c=(8\pm 1)$K, upper critical field ${\mathrm{\mu }}_0{H}_{c2}\left(0\right)=(20\pm 5)$T, and coherence length $\xi \left(0\right)=(40\pm 3)$Å. We show that our extrapolated results for the amorphous TiZrNb alloy would be similar to that of crystalline TiZrNb, except for superconducting properties (most notably the upper critical field $H_{c2}\left(0\right)$), which might be attributed to the strong topological disorder of the amorphous phase. Also, we offer an explanation of the discrepancy between the variations in $T_c$ with the average number of valency electrons in neighboring alloys of 4d transition metals and some high-entropy alloys. Overall, we find that our novel method of systematic analysis of results is rather general, as it can provide reliable estimates of the properties of any alloy which has not been prepared as yet. Full article

N-heterocyclic carbenes (NHCs) were first isolated as stable species by Arduengo in 1991. Since then, they have expanded the boundaries of carbene chemistry and sparked extensive research. Utilizing NHCs to modify the electronic properties of transition metal complexes represents a significant advancement in the field. Pincer-type NHCs, which occupy half or more of the vacant sites on metal centers, typically result in structurally well-defined molecular platforms with specific active sites for a variety of applications. This review provides an overview of late transition metal complexes based on pincer-type NHCs, discussing their synthetic strategies, reactivities, and electronic properties, as well as their applications. Additionally, some perspectives will be presented to highlight future directions in this rapidly growing field. Full article

Recent archaeological sites dating to the late 19th and early 20th centuries have rarely been studied to date. Among the 500 “glassy” beads excavated from Dohouan (Côte d’Ivoire), elemental analyses reveal that fewer than half contain abnormally high alumina contents, associated with a soda–potash–lime flux (three compositional groups). The remaining beads are typical lead-based glass. The Raman spectra of the alumina-rich beads are quite complex due to their glass–ceramic nature, combining features similar to the vitreous phase of porcelain glaze with the presence of various crystalline phases (quartz, wollastonite, calcium phosphate, calcite). Organic residues are also observed. Colors are primarily produced by transition metal ions, although some specific pigments have also been identified. These characteristics suggest that the alumina-rich beads were manufactured by pressing followed by sintering, as described in patents by Richard Prosser (1840, UK) and Jean Félix Bapterosse (1844, France). A comparison is made with beads from scrap piles at the site of the former Bapterosse factory in Briare, France. This process represents one of the earliest examples of replacing traditional glassmaking with a ceramic process to enhance productivity and reduce costs. Full article

Recent advances in designing multinuclear late transition metal catalysts for the oligo-/polymerization of olefins emphasize the great interest and promising approaches in the preparation and application of these catalytic systems. Accordingly, in this study, two dinuclear macrocyclic bis(iminopyridine) Fe- and Co-based complexes (FC and CC) were prepared at moderate yields through a one-pot template reaction. Upon activation by MMAO, not only did the catalysts show reasonable activities for the oligomerization of ethylene but also showed high selectivity for the production of tetramers (α-C₈). With respect to the catalyst structure, FC demonstrated higher catalyst activity (9.45 g mol⁻¹ Fe h⁻¹ × 10⁵ vs. 8.75 × 10⁵ g mol⁻¹ Co h⁻¹) along with higher selectivity for α-C₈ production compared to CC (96.6 vs. 96.1%). Both catalysts had thermal stability up to 70 °C, with FC being much more active and stable than CC under identical conditions. On the other hand, polymerization parameters had an influence on the catalyst performance and oligomer distribution. Moreover, molecular calculations were employed for geometry optimization and structural determination, which was consistent with the experimental results. Full article

Approaches capable of simultaneously treating cancer and protecting susceptible patients from lethal infections are highly desirable, although they prove challenging. Taking inspiration from the well-known anticancer platinum complexes, successive studies about the complexation of organic compounds with other late transition metals, such as silver, gold, palladium, rhodium, ruthenium, iridium, and osmium, have led to remarkable anticancer activities. Among the numerous chemical moieties studied, N-heterocyclic carbenes (NHCs) have revealed very attractive activities due to their favorable chemical properties. Specifically, gold–NHC complexes emerged as some of the most active complexes acting as antitumor agents. On the other hand, some recent studies have highlighted the involvement of these complexes in antiviral research as well. The well-known gold-based, orally available complex auranofin approved by the Food and Drug Administration (FDA) for the treatment of rheumatoid arthritis has been suggested as a repositioned drug for both cancer and viral infections. In the era of the COVID-19 pandemic, the most interesting goal could be the discovery of gold–NHC complexes as dual antiviral and anticancer agents. In this review, the most recent studies regarding the anticancer and antiviral activities of gold(I)–NHC complexes will be analyzed and discussed, offering an interesting insight into the research in this field. Full article

Late transition metal olefin polymerization catalysts have received more attention in the field of catalytic olefin polymerization. Barrelene-based α-diimine nickel and palladium olefin polymerization catalysts are rising stars because of their backbone structure and catalytic properties. In this review, we present a comprehensive review of barrelene-derived α-diimine nickel and palladium olefin polymerization catalysts. α-Diimine nickel and palladium catalysts are introduced from two aspects: barrelene-derived backbone and aniline derivatives with different substituents. The relationship between catalyst structure and catalytic properties is also emphasized. This review attempts to provide an inspiration for the design of high-performance barrelene-based catalysts. Full article

As a kind of high-performance thermoplastic crystalline resin, poly(4-methyl-1-pentene) (PMP) is characterized by its low density, low dielectric constant, exceptional mechanical and chemical properties, high transparency, and gas permeability. PMP has recently received more attention since COVID-19, because it is used as a hollow-fiber membrane for extracorporeal membrane oxygenation (ECMO) based on its high permeability and excellent biocompatibility. This review summarizes the chemical structure, synthesis, properties, and application of PMP. The advancements in catalyst systems for the catalytic synthesis of PMP, including Ziegler–Natta, metallocene, post-metallocene, and late-transition metal catalysts are emphasized. Furthermore, the molecular chain structure, helical conformation, and crystallization morphology of PMP, as well as its properties and applications, are also introduced in detail. Additionally, PMP composites and functional PMP materials are also described as promising and high-performance materials. Full article

The strict connections/interactions between microbial infections and cancer are nowadays widely accepted. Hence, the dual (or multiple) targeting of microbial infections and cancer is an essential issue to be addressed. In this context, metal complexes have gained considerable importance and effectiveness in medicinal chemistry. Particularly, N-heterocyclic carbene (NHC) complexes with transition metals have emerged as very promising compounds. Among the myriad of NHC–metal complexes, those bearing silver will be the subject of this review. Numerous Ag(I)-NHC complexes have revealed high antibacterial and/or anticancer properties, even higher than those of reference drugs. Herein, we summarize the most recent studies while also discussing the proposed mechanism of action and offering an interesting remark about the research in this field. Literature databases (PubMed/MEDLINE, Scopus, and Google Scholar) were used as sources to search the literature, referring to the last five years. Full article

The conducted study shows that apatite is one of the key accessory minerals in the ultramafic-mafic rocks of the Khudolaz differentiated complex in the Southern Urals, including late pegmatoid gabbro. Petrographic and mineralogical investigations determine apatite crystallizing simultaneously with hornblende in pegmatoid gabbro from the residual water-saturated melt after plagioclase crystallization at a temperature of 990–800 °C, a pressure of 1–3 kbar, oxygen fugacity from −13.9 to −10.7, and water content of 3.9–5.5 wt. %. Pegmatoid gabbro apatite (Ap_pg) from the Severnyi Buskun composite massif differs from early ultramafic-mafic apatite having a fairly high potential for sulfide-platinum metal mineralization in low chlorine and high fluorine content. Low sulfur concentrations in Ap_pg testify to the lack of sulfide-platinum metal mineralization potential of pegmatoid gabbro, but a scanty potential for rare-metal mineralization (e.g., REE) is possible. Ap_pg is quite poor in REE despite the enrichment of pegmatoid gabbros in REE relative to early ultramafic-mafics, which indicates REE accumulation in the fluid. The ratios of cerium and europium anomalies characterize the Ap_pg crystallization under conditions transitional from the magmatic to the hydrothermal stage. Generally, apatite is a good indicator of the difference in the conditions of formation of late pegmatoid gabbro and early ultramafic-mafic rocks, which determines the importance of this mineral in mineralogical and petrological studies. Full article

The large-scale vein-type Zn-Pb-Ag deposit in the Eastern Qinling Orogen (EQO) has sparked a long-standing debate over whether magmatism or metamorphism was the primary control or factor in its formation. Among the region’s vein-type deposits, the large-sized Bailugou deposit offers a unique opportunity to study this style of mineralization. Similar to other deposits in the area, the vein-type orebodies of the Bailugou deposit are hosted in dolomitic marbles (carbonate–shale–chert association, CSC) of the Mesoproterozoic Guandaokou Group. Faults control the distribution of the Bailugou deposit but do not show apparent spatial links to the regional Yanshanian granitic porphyry. This study conducted comprehensive H–O–C–S–Pb isotopic analyses to constrain the sources of the ore-forming metals and metal endowments of the Bailugou deposit. The δ³⁴S_CDT values of sulfides range from 1.1‰ to 9.1‰ with an average of 4.0‰, indicating that the sulfur generated from homogenization during the high-temperature source acted on host sediments. The Pb isotopic compositions obtained from 31 sulfide samples reveal that the lead originated from the host sediments rather than from the Mesozoic granitic intrusions. The results indicate that the metals for the Bailugou deposit were jointly sourced from host sediments of the Mid-Late Proterozoic Meiyaogou Fm. and the Nannihu Fm. of the Luanchuan Group and Guandaokou Group, as well as lower crust and mantle materials. The isotopic composition of carbon, hydrogen, and oxygen collectively indicate that the metallogenic constituents of the Bailugou deposit were contributed by ore-bearing surrounding rocks, lower crust, and mantle materials. In summary, the study presents a composite geologic-metallogenic model suggesting that the Bailugou mineral system, along with other lead-zinc-silver deposits, porphyry-skarn molybdenum-tungsten deposits, and the small granitic intrusions in the Luanchuan area, are all products of contemporaneous hydrothermal diagenetic mineralization. This mineralization event transpired during a continental collision regime between the Yangtze and the North China Block (including syn- to post-collisional settings), particularly during the transition from collisional compression to extension around 140 Ma. The Bailugou lead-zinc-silver mineralization resembles an orogenic-type deposit formed by metamorphic fluid during the Yanshanian Orogeny. Full article

Late transition metal catalysts represent a significant class of olefin polymerization catalysts that have played an essential role in advancing the polyolefin industry owing to their highly tunable ligands and low oxophilicity. A key feature for the design of late transition metal catalysts lies in the steric bulk of the o-aryl substituents. Bulky 8-arylnaphthylamines have emerged as a promising aniline candidate for conducting high-performance catalysts by introducing axially steric hindrance around the metal center. This review focuses on late transition metal (Ni, Pd, Fe) catalysts derived from 8-arylnaphthylamines, surveying their synthesis, structural features, and catalytic applications in olefin (co)polymerizations. Additionally, the relationship between catalyst structure and catalytic performance is discussed, highlighting how these unique ligand systems influence polymerization activity, molecular weight, and polymer branching. Full article

For square-planar late transition metal pyridine, diimine (Rh, Ir) complexes with hydro-xido, methoxido, and thiolato ligands. We could previously establish sizable metal-O- and S π-bonding interactions. Herein, we report the hydrogenation studies of iridium hydroxido and methoxido complexes, which quantitatively lead to the trihydride compound and water/methanol. The iridium trihydride displays a highly fluctional structure with scrambling hydrogen atoms, which can be described as a dihydrogen hydride system based on NMR and DFT investigations. This contrasts the iridium sulfur compounds, which are not reacting with dihydrogen. According to DFT and LNO-CCSD(T) calculations, hydrogenation of the methoxido complex proceeds by a two-step mechanism, i.e., an oxidative addition step of H₂ to an Ir(III) dihydride intermediate with consecutive reductive O-H elimination of methanol. Based on PNO-CCSD(T) calculations, the reactivity difference between the O- and S-donors can be traced to the stronger H-O bonds in the water/methanol products compared to the S-H bonds in the sulphur congeners, which serves as a driving force for hydrogenation. Full article

The main goal of this paper is to determine the order of the paragenetic sequence and phase transitions of the Ni–Fe sulfide association hosted in listvenites. Listvenites are hydrothermally altered mafic and ultramafic rocks that are often associated with active tectonic settings, such as transform faults, suture zones, and regional extensional faults, usually in contact with volcanic or carbonate rocks. Listvenitization is displayed by a carbonation process when the original olivine, pyroxene, and serpentine group minerals are altered to Mg–Fe–Ca carbonates (magnesite, calcite, dolomite, and siderite), talc, quartz, and accessory Cr spinel, fuchsite, and Ni–Fe sulfides. The formed rocks are highly reactive; therefore, very often, younger hydrothermal processes are observed, overprinting the mineralogy and geochemistry of the original listvenitization products, including accessory Ni–Fe sulfide paragenesis. The studied samples of listvenites were collected from two locations in Kosovo (Vardar Zone): Janjevo and Melenica. The Ni–Fe sulfide textures and relationships with the surrounding listvenite-hosted minerals were obtained using reflected and transmitted light microscopy, while their chemical composition was determined using an electron microprobe. They form accessory mono-or polymetallic aggregates that usually do not exceed 100 μm in size disseminated in the studied listvenites. Generally, the paragenetic sequence of Ni–Fe sulfides is divided into three stages. The first pre-listvenite magmatic phase is represented by pentlandite and millerite. The second listvenite stage consists of Ni–Co bearing pyrite I (Ni content up to 11.57 wt.% [0.24 apfu], and Co content up to 6.54 wt.% [0.14 apfu]) and differentiated thiospinels (violarite + siegenite ± polydymite). The last, late listvenite stage is represented by younger gersdorffite−ullmannite and base metal mineralization: pyrite + marcasite + sphalerite + galena ± chalcopyrite ± sulfosalts. The findings obtained should help in the interpretation of many disseminated accessory Ni–Fe–Co mineralizations associated with mafic and ultramafic rocks worldwide. Full article

The α-diimine late transition metal catalyst represents a new strategy for the synthesis of atactic polypropylene elastomer. Taking into account the properties of the material, enhancing the molecular weight of polypropylene at an elevated temperature through modifying the catalyst structure, and further increasing the activity of α-diimine catalyst for propylene polymerization, are urgent problems to be solved. In this work, two α-diimine nickel(II) catalysts with multiple hydroxymethyl phenyl substituents were synthesized and used for propylene homopolymerization. The maximum catalytic activity was 5.40 × 10⁵ gPP/molNi·h, and the activity was still maintained above 10⁵ gPP/molNi·h at 50 °C. The large steric hindrance of catalysts inhibited the chain-walking and chain-transfer reactions, resulting in polypropylene with high molecular weights (407~1101 kg/mol) and low 1,3-enchainment content (3.57~16.96%) in toluene. The low tensile strength (0.3~1.0 MPa), high elongation at break (218~403%) and strain recovery properties (S.R. ~50%, 10 tension cycles) of the resulting polypropylenes, as well as the visible light transmittance of approximately 90%, indicate the characteristics of the transparent elastomer. Full article

Ultra-high molecular weight polyethylenes (UHMWPEs) are significant engineering plastics for their unique properties, such as high impact resistance, abrasion resistance, weatherability, lubricity, and chemical resistance. Consequently, developing a suitable catalyst is vital in facilitating the preparation of UHMWPE. The late transition metal catalysts have emerged as effective catalysts in producing UHMWPE due to their availability, enhanced tolerance to heteroatom groups, active polymerization characteristics, and good copolymerization ability with polar monomers. In this review, we mainly focus on the late transition metal catalysts, summarizing advancements in their application over the past decade. Four key metals (Ni, Pd, Fe, Co) for generating linear or branched UHMWPE will be primarily explored in this manuscript. Full article