Mechanism and Stereoselectivity Control of Terminal Alkyne Dimerization Activated by a Zr/Co Heterobimetallic Complex: A DFT Study.

Heterobimetallic complexes have recently garnered considerable attention in organic synthesis owing to their high activity and selectivity, which surpass those of monometallic complexes. In this study, the detailed mechanisms of terminal alkyne dimerization activated by the heterobimetallic Zr/Co complex, as well as the different stereoselectivities of Me3SiC≡CH and PhC≡CH dimerization, were investigated and elucidated by using density functional theory calculations. After excluding the three-molecule reaction and outer-sphere mechanisms, the inner-sphere mechanism was determined as the most optimal process. The inner-sphere mechanism involves four processes: THF dissociation and coordination of the first alkyne; ligand migration and C-H activation; N2 dissociation and insertion of the second alkyne; and reductive elimination. The stereoselectivity between the E-/Z- and gem-isomers is determined by the C-C coupling mode of the two alkynes and that of the E- and Z-isomers is determined by the sequence of the C-C coupling and hydrogen migration in the reductive elimination process. Me3SiC≡CH dimerization yields only an E-isomer owing to the large differences in the distortion and interaction energies, whereas PhC≡CH dimerization produces an E-, Z-, and gem-isomers owing to the reduced interaction energy differences.

Small molecules (CO2 , iPrNCO, and iPrNCNiPr) activation by the metallomimetics (µ-Hydrido) diborane anion: A DFT investigation on mechanism and chemoselectivity controlling.

Main-group metallomimetics provide a new way to replace transition metal complexes to activate inert small molecules under mild conditions. In this work, the activation mechanisms of CO2 , iPrNCO, and iPrNCNiPr by (µ-Hydrido) diborane anion ([1H]- ) have been investigated by density functional theory (DFT) calculations. Two different activation sites, BB versus BH bond of [1H]- , are investigated and compared. The results show that these inert molecules can be activated by [1H]- through cycloadditions under mild conditions. The reactions with iPrNCO and iPrNCNiPr are dynamic and thermodynamic controlling, the obtained products are related not only to the energy barrier but also to the stability of the products. Moreover, the competition for BB/BH bond site activation is directly related to the steric effect of small molecules. CO2 , which is without steric hindrance, can only be activated by the BB bond, whereas iPrNCNiPr can only be activated by the BH bond due to the large steric effect. The medium iPrNCO can be activated not only by the BB bond but also by the BH bond. Our study provides theoretical explanations for the reaction activity and chemoselectivity controlling of the title reaction, and displays the potential applications for compounds containing boron-boron bonds and inert small molecule activation.

Gold(III) derivatives as the noncovalent interaction donors: theoretical study of the π-hole regium bonds.

Except for the well-known σ-hole regium bonds formed by metal nanoparticles and M(I) (M = Cu, Ag, and Au) derivatives, the existence of π-hole regions located above and below the Au atom in gold(III) derivatives suggests that gold(III) also functions as an efficient electrophilic site. In this study, a comprehensive analysis was conducted on the electrophilicity of trichloro-(p-toluonitrilo-N)-gold(III) derivatives AuL3(NCC6H4X) (L = Cl, Br, CN; X = NH2, CH3, CF3, NC, and CN) and the nature of π-hole regium bonds in the AuL3(NCC6H4X)⋯LB (LB = NH3, N(NH3)3, CH2O, C2H2, C2H4, C6H6) and (AuCl3(NCC6H4Y))n (Y = Cl, CN, NC, NO2; n = 2, 3)) complexes. The characteristics of the π-hole regium bonds were studied with respect to the influence of ligands and substituents, the strength of intermolecular interactions between Au(III) derivatives and Lewis bases, and those in the polymers. In the case of the AuL3(NCC6H4X)⋯NH3 complexes, the strength of the regium bonds increases gradually in the order of L = Cl < Br < CN and X = NH2 < CH3 < CF3 ≈ NC < CN. The ligands (L) attached to the Au atom exert a significant effect on the strength of the π-hole regium bonds in comparison to the substituents (X) on the benzene ring. The regium bonds are primarily dominated by electrostatic interaction, accompanied by moderate contribution from polarization. Linear relationships were identified between the electrostatic energies and the local most positive potentials over the Au atom, as well as between the polarization energies and the amount of charge transfer. Most of the π-hole regium bonds in the AuL3(NCC6H4X)⋯LB complexes exhibit the characters of closed shell noncovalent interactions. In the polymers (AuCl3(NCC6H4Y))n, weak face-to-face π-π stacking interactions are also present, in addition to regium bonds. The trimers displayed a slightly negative cooperativity in comparison to the dimers.

Intrinsic defects at the interface of the FAPbI3/MAPbI3 superlattice: insight from first-principles calculations.

The use of a superlattice structure is an effective strategy to develop novel perovskites and obtain excellent light-absorbing materials. Based on first-principles calculations, we systematically studied the properties of intrinsic point defects at the interface of the FAPbI3/MAPbI3 superlattice. Our calculations show that charged defects are easier to form as compared to neutral ones at the superlattice interface due to low formation energies. Most defects with low formation energies have a shallow level in the band gap, and some deep level defects have high formation energies, so the superlattice perovskite exhibits high defect tolerance. PbI3+ is a dominant and detrimental defect, which acts as a non-radiative recombination center because it has low formation energy and a deep transition level. To avoid the generation of PbI3+ defects, it is suggested to synthesize FAPbI3/MAPbI3 superlattices under I-rich conditions. The calculated light absorption coefficients and photovoltaic performance parameters demonstrate that the presence of defects leads to a certain degree of reduction in light absorption and power conversion efficiency (PCE) of solar cells made of FAPbI3/MAPbI3 superlattices, but the excellent performance of the perovskite solar cell (PSC) is basically retained. The superlattice perovskites are still promising candidates for light-absorbing materials of PSCs. This study is expected to contribute to a better understanding of the properties of defects at the superlattice interface and provide theoretical support for the design of high performance PSCs.

Arginine-Glycine-Aspartic Acid-anchored Curcumin-based Nanotherapeutics Inhibit Pyroptosis-induced Cytokine Release Syndrome for In Vivo and In Vitro Sepsis Applications.

AIM: We aimed to design RGD-anchored liposomes encapsulating an antipyroptosis drug that could efficiently target macrophages and relieve the rate of cytokine release syndrome, providing a new strategy for sepsis treatment, especially sepsis-induced acute renal injury. BACKGROUND: Sepsis is a clinical syndrome of life-threatening organ dysfunction caused by host response disorders due to infection. Sepsis has a high incidence and remains one of the leading causes of death worldwide. OBJECTIVE: Macrophage-mediated pyroptosis plays an important role in the occurrence and development of cytokine release syndrome and organ injury caused by sepsis. Curcumin can inhibit inflammasome assembly and slow the progression of pyroptosis by scavenging intracellular reactive oxygen species, but it has poor water solubility and low bioavailability. The emergence of drug-delivery nanosystems has overcome this problem, but there is still a lack of research on how to accurately deliver antipyroptotic drugs to innate immune cells and subsequently hinder pyroptosis. METHODS: We constructed a curcumin-loaded RGD-modified liposome (RGD-lipo/Cur) and demonstrated that RGD-lipo/Cur could effectively target macrophages. RESULTS: In vitro, RGD-lipo/Cur reduced the upregulation of caspase-1, caspase-3, NLRP3, IL-1ß and GSDMD, inhibiting pyroptosis, reducing oxidative stress, and attenuating the proinflammatory cytokine cascade. CONCLUSION: RGD-lipo/Cur was considered to have great potential for sepsis treatment.

Evolutionary game model of construction enterprises and construction material manufacturers in the construction and demolition waste resource utilization.

With the continuous advancement of urbanization, a huge amount of construction and demolition waste (CDW) is generated in large-scaled construction activities, which has aggravated the problem of environmental pollution, waste of resources and destruction of city appearance. In the context of waste-free city, the recycling of CDW can reduce environmental pollution and promote the sustainable development of a city. However, only 20-30% of CDW in the world is recycled, showing a low rate of global CDW utilization. In order to improve the utilization rate, this paper selects construction enterprises and construction material manufacturers as main participants, applies evolutionary game theory to construct an evolutionary game model on the two parties' decision-making behaviors in CDW recycling, and uses MATLAB to make a numerical simulation. The aim of the model is to analyze the influence of various factors on the parties' decision-making behavior evolution and propose strategies to promote CDW utilization. The study found that the stable state of the CDW resource utilization system mainly depends on the difference between revenue and costs, the initial strategy, and the strength of the external environment; for the government, a supervision strategy is found to be necessary, and the best supervision level is 0.6. In the early stage of resource utilization of CDW, subsidies to construction material manufacturers should be increased to improve their initial participation; public participation can effectively improve the efficiency of government supervision, and its optimal participation level is greater than or equal to 0.4; under weak supervision, government penalty increases alone cannot prevent construction enterprises from illegally disposing of CDW. Therefore, the greater the difference, the positive the initial strategy, and the stronger the external environment, the more the behavior of the two participants tends to be {participation, use}. The results show that the government should establish effective supervision mechanisms and legal systems, improve supervision hotlines and information platforms, encourage the public to participate in CDW management and supervision, set appropriate rewards and punishments, strengthen supervision and management levels, reduce supervision costs, and ensure the effectiveness of construction management to improve the efficiency of cooperation between construction enterprises and construction material manufacturers.

Measurement and Prediction of Urban Land Traffic Accessibility and Economic Contact Based on GIS: A Case Study of Land Transportation in Shandong Province, China.

As the basic support of regional economic and social development, land transportation is one of the important engines to promote regional development, and its construction and improvement will have an important impact on the regional economic pattern. Based on the road network of Shandong Province, China, in 2020, according to the Medium and Long-term Development Plan of Comprehensive Transportation Network of Shandong Province (2018-2035), this paper uses the GIS network analysis method, weighted average travel time, modified gravity model and other methods to study the land traffic accessibility and economic relation intensity of prefecture-level cities in Shandong Province, China, in 2020 and 2035. The results show that the distribution of land traffic accessibility in Shandong Province, China, shows a certain regional main road pointing characteristic in 2020, and the urban accessibility level gradually decreases along the Beijing-Shanghai high-speed railway and Jinan-Qingdao high-speed railway to the periphery. In 2035, the land traffic accessibility of Shandong Province, China, will be more spatially distributed as "concentric circles". From 2020 to 2035, the urban land traffic accessibility and the balance of economic contact in Shandong Province, China, will be improved significantly. The research results can provide a theoretical reference for optimizing the traffic network pattern and promoting urban economic contact in Shandong Province, China.

Matrix Regeneration Ability In Situ Induced by a Silk Fibroin Small-Caliber Artificial Blood Vessel In Vivo.

The success of a small-caliber artificial vascular graft in the host in order to obtain functional tissue regeneration and remodeling remains a great challenge in clinical application. In our previous work, a silk-based, small-caliber tubular scaffold (SFTS) showed excellent mechanical properties, long-term patency and rapid endothelialization capabilities. On this basis, the aim of the present study was to evaluate the vascular reconstruction process after implantation to replace the common carotid artery in rabbits. The new tissue on both sides of the SFTSs at 1 month was clearly observed. Inside the SFTSs, the extracellular matrix (ECM) was deposited on the pore wall at 1 month and continued to increase during the follow-up period. The self-assembled collagen fibers and elastic fibers were clearly visible in a circumferential arrangement at 6 months and were similar to autologous blood vessels. The positive expression rate of Lysyl oxidase-1 (LOXL-1) was positively correlated with the formation and maturity of collagen fibers and elastic fibers. In summary, the findings of the tissue regeneration processes indicated that the bionic SFTSs induced in situ angiogenesis in defects.

The role of halogen bonds in the catalytic mechanism of the iso-Nazarov cyclization reaction: a DFT study.

With the continuous development of halogen bonds, halogen bond donors have been used as clean and efficient catalysts in organic reactions. In this work, with inorganic halides (I2, IBr, ICl, and ICl3) as catalysts and the iso-Nazarov cyclization as the benchmark reaction, we aim at investigating the role of the halogen bond in the catalytic mechanism. The halogen bond catalyzed iso-Nazarov cyclization reaction involves three steps: carbon-carbon coupling process, [1,2]-H shift process, and [1,4]-H shift process. The halogen-bonding interaction promotes the charge accumulation of the oxygen atom in the carbonyl group and decreases the activation energy of the reaction. The catalytic activity of the halogen bond donor is enhanced in the order of I2 < IBr < ICl < ICl3, and it could be predicted that the partial covalent interaction of the I⋯O halogen bond between the catalyst ICl3 and the oxygen atom of the reactant may exhibit good catalytic activity in the experiments. In the [1,4]-H shift process, the two-step hydrogen bond/halogen bond co-catalyzed mechanism exhibits the lowest reaction energy barrier than the one-step water co-catalyzed proton transfer mechanism and the direct one.

To study the mechanism of Scutellariae Radix and Astragaloside in the treatment of lung cancer based on network pharmacology.

The aim of the study wasto explore the target and potential mechanism of Scutellariae Radix and Astragaloside in the treatment of lung cancer infection by network pharmacology. The target information of baicalein and flavonin was mined from CTD database and Swiss database. Genecards database, DRUGBANK database, and OMIM database were used to search for lung cancer related genes. The target protein network map (PPI) was drawn by using the STRING database analysis and Cytoscape3.7.1 software. With the help of Perl language, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and gene function analysis (GO) enrichment analysis were carried out by using the biological program package of R language. In total, 347 biological targets of Astragaloside and Scutellariae Radix were identified through the collection and analysis of multiple databases. In total, 1526 lung cancer targets were obtained from a multi-disease database. The "component-target" network of Astragaloside and Scutellariae Radix was constructed, and the protein interaction network (PPI) of the overlapping targets was analyzed to identify the key targets of drug-influenced diseases. In addition, KEGG pathway analysis and GO enrichment analysis were performed on the overlapping targets to explore the mechanism of Scutellariae Radix and Astragaloside in the treatment of lung cancer. Scutellariae Radix and Astragaloside have the characteristics of multi-component, multi-target and multi-pathway in the treatment of lung cancer, which provides a new idea and scientific basis for further research on the molecular mechanism of the antilung cancer effect of Scutellariae Radix and Astragaloside.

Mechanism, Stereoselectivity, and Role of O2 in Aza-Diels-Alder Reactions Catalyzed by Dinuclear Molybdenum Complexes: A Theoretical Study.

The aza-Diels-Alder-type reaction between imines and functionalized alkenes is one of the most versatile approaches to obtain piperidine derivatives. When using the Lewis acid [Mo2(OAc)4] (CAT) as a catalyst, it was found that the activation of CAT by O2 was essential for an efficient reaction. In this paper, the mechanism and stereoselectivity of the aza-Diels-Alder reaction between aromatic acyl hydrozones 1 and Danishefsky diene 2 under uncatalyzed and catalyzed (CAT not activated by O2 and CAT activated by O2) conditions have been studied by density functional theory (DFT) calculation. The results show that the uncatalyzed reaction is difficult to proceed at room temperature due to the high energy barrier. The CAT not activated by molecular oxygen has catalytic activity but not too much. When CAT is activated by O2, CATO2 may be the correct catalytic species, which results in a dramatic increase of reaction activity. The reaction mechanisms with/without the catalyst are different. The uncatalyzed reaction is concerted for both the endo and exo pathways. For the CAT-catalyzed reaction, the endo pathway is concerted, but the exo pathway is nonconcerted and involves two steps. The endo product is the main product for the reaction catalyzed by CAT, while for reactions catalyzed by CATO1 and CATO2, the endo and exo products can be obtained. The reaction activity is directly correlated to the atomic charges of two coupling C atoms. Our work explains the experimental results, determines the structure of the O2-activated catalyst species, and provides predictions for the reaction activity and stereoselectivity controlling.

BF3 -Catalyzed Mukaiyama aldol reaction of acetaldehyde with 2-siloxy-1-propene.

The Mukaiyama aldol reaction is a powerful tool for the construction of the carbon-carbon bond and the formation of ß-hydroxycarbonyl compounds. In this work, the mechanism of acetaldehyde and 2-siloxy-1-propene both in the absence and presence of the catalyst BF3 was investigated based on density functional theory. The mechanism includes two major steps: the formation of the carbon-carbon bond and the removal of SiH3 /BF2 by water. The energy barrier of the carbon-carbon bond formation process in the presence of BF3 is obviously lower, indicating that BF3 is a good catalyst for this reaction. In terms of molecular configuration, the different tensions between the five-membered-ring and six-membered-ring can be considered as the possible reason for the catalytic effect of BF3 . In terms of charge transfer, the charges of natural population analysis in the carbon atom of the carbonyl group in acetaldehyde becomes more positive, which is easier to attack by nucleophiles and promote the nucleophilic process.

Competition and conversion between pnicogen bonds and hydrogen bonds involving prototype organophosphorus compounds.

Ab initio calculations have been performed to investigate the competition and conversion between the pnicogen bonds and hydrogen bonds in complexes containing prototype organophosphorus compounds RPO2 (R = CH3 and CH3O). The competition between the pnicogen bonds and hydrogen bonds is controlled by the magnitude of Vs,min and Vs,max in the prototype organophosphorus compounds. Monomeric methyl metaphosphate (CH3OPO2), with more positive π-holes, is more likely to form pnicogen bonds with different electron donors, such as NH3, H2O, HNC and HCCH. Methoxyphosphinidene oxide (trans- and cis-CH3OPO) is inclined to form hydrogen bonds with H2O, HNC and HCCH. Most of the pnicogen bonds have covalent or partially covalent character, while most of the hydrogen bonds exhibit the noncovalent characteristics of weak interactions. The mechanisms of three typical conversions between the pnicogen bond and the hydrogen bond have been investigated and the breakage and formation of the bonds along the reaction pathways have been analyzed using topological analysis of electron density. For the three studied conversion processes, the transformation between the hydrogen-bonded complex and pnicogen-bonded complex is achieved readily through several T-shape structure transition states.

Comparison of Anion-Anion Halogen Bonds with Neutral-Anion Halogen Bonds in the Gas Phase and Polar Solvents.

In recent years, anion-anion halogen bonds and neutral-anion halogen bonds have received extensive attention. In this work, the possibility of halogen bonding of neutral and anionic forms of para-substituted iodine derivatives of dithiobenzoic acid and its Se- and Te-based congeners with halide anions has been investigated. The anion-anion complexes are not favorable in the gas phase because of the repulsive effect between anionic halogen bond donors and acceptors. A local minimum is present in the potential energy surface between the - S2 CC6 H4 I and X (X=F- , Cl- , Br- ), and the anion-anion complexes - S2 CC6 H4 I ⋅⋅⋅ X(X=F- , Cl- , Br- ) are metastable in the gas phase. Solvation is beneficial to the formation of the anion-anion complexes. The neutral-anion complexes are stable in both the gas phase and the polar solvents. The anion-anion halogen bonds tend to be stable in polar solvents, while the neutral-anion halogen bonds are stronger in the gas phase than in solvents.

Computational prediction on the catalytic activity of heterobimetallic complex featuring MM' triple bond in acetylene cyclotrimerization: Mechanistic study.

A detailed reaction mechanism of acetylene cyclotrimerization catalyzed by V(i PrNPMe2 )3 Fe-PMe3 (denote as CAT), a heterobimetallic complex featuring V-Fe triple bond, was computationally investigated using density functional theory. The calculated results show that the first acetylene firstly attaches to the V atom of CAT to get a four-membered ring structure through [2 + 2] cycloaddition reaction. For the second acetylene addition, there are two cyclotrimerization mechanisms, outer sphere mechanism and inner mechanism. The inner sphere reaction pathway is the main reaction pathway. By replacing the V with Nb and Ta, Fe with Ru and Os, a series of new catalysts are screened computationally. The calculated results show that, all of the nine heterobimetallic complexes show high activity at mild condition. The energy barrier of the rate determining step is related to the natural population analysis (NPA) charge of M' and the Wiberg bond index (WBI) of M-M' bond. The more negative NPA charge of M' and the smaller WBI of M-M' bond, the lower energy barrier is.

Substituent-regulated mechanism on reaction Cp2NbH3 (Cp = η5-C5H5) with RC[triple bond, length as m-dash]CR (R = COOMe and Me).

The reaction of alkynes with bis-cyclopentadienyl hydride complexes of niobium has aroused substantial concern due to their important roles in catalytic hydrogenation processes. In this paper, the reaction mechanisms of Cp2NbH3 (Cp = η5-C5H5) with substituted alkynes RC[triple bond, length as m-dash]CR (R = COOMe (1) and Me (2)) were investigated and compared based on density functional theory (DFT) calculations. The calculated results demonstrate that the reaction mechanisms and products of the title reactions are regulated by the characteristics of the alkyne substituent. For alkynes that feature the electron-withdrawing substituent COOMe, the corresponding fumaric ester complex, namely, Cp2NbH(trans-MeO2CCH[double bond, length as m-dash]CHCO2Me), can be obtained at ambient temperature through an insertion process. For alkynes that feature the electron-donating substituent Me, the products are hydride niobocene Cp2NbH(MeC[triple bond, length as m-dash]CMe) and H2, which are obtained via the elimination of hydrogen molecules, and they can only be obtained with irradiation by UV light. Our studies provide reasonable explanations for experimental observations and predict new chemical reactions in this domain.

Electronic structure of triangular M3 (M = B, Al, Ga): nonclassical three-center two electron π bond and σ delocalization.

The small molecule clusters have received more and more attention due to their widespread applications in chemical insulators, explosives, semiconductors and the high energy density materials industry. The electron deficiency of group IIIA elements endows their clusters with interesting properties. In this work, the electronic structures of M3 (M = B, Al, Ga) have been investigated by means of a complete active space self-consistent field (CASSCF) method. The nature of the chemical bond has been analyzed using the quantum theory of atoms in molecules (QTAIM) and electron localization function (ELF) analyses. The following conclusions can be drawn: in M3 (M = B, Al, Ga) clusters, two π electrons are shared by three atoms forming a 3c-2e delocalization π bond. Going from B3 to Al3 to Ga3, more and more electrons move from the bond pair to the outside of the M atom, which leads to a gradual enhancement of the delocalization of σ electrons. Aromaticity and the adaptive natural density partitioning (AdNDP) analyses reveal the existence of the 3c-2e π bond and delocalization of σ electrons in the studied systems.

Organocatalysis by Halogen, Chalcogen, and Pnictogen Bond Donors in Halide Abstraction Reactions: An Alternative to Hydrogen Bond-Based Catalysis.

The application of σ-hole interactions (halogen, chalcogen, and pnictogen bonds) in organocatalysis has attracted more and more interest in recent years. The catalysis mechanism of halogen, chalcogen, and pnictogen bonds in the chloride abstraction from Reissert-type substitution of isoquinoline has been investigated by the density functional theory. Compared with the reaction without catalysts, the reactions catalyzed by the σ-hole interactions have lower energy barriers and are more favorable. The formation of the σ-hole interaction between the Cl atom and halogen, chalcogen, and pnictogen bond donors facilitates the chloride abstraction reaction by weakening the strength of the C-Cl bond and decreasing the HOMO-LUMO gap of the reactants. The catalytic activity follows the sequence of pnictogen bonds > chalcogen bonds > halogen bonds and shows an increase from period 3 to 5 in the same group, and pnictogen bond donors, especially tris (pentafluorophenyl) antimony, show the best catalysis performance.

Enhancing the stability of perovskites by constructing heterojunctions of graphene/MASnI3.

In this paper, the geometric and electronic properties of heterojunctions constructed using a graphene sheet and an MASnI3 surface were investigated by performing first-principles calculations based on the density functional theory. Our results show that the interaction between graphene and the MASnI3 surface is in the scope of van der Waals interactions. In the heterojunctions, electrons transfer from graphene to the MASnI3 surface, resulting in the formation of a built-in electric field in the interface, which is favorable for the separation of electrons and holes. The absorption spectra showed that the absorption intensity of the heterojunction in the visible region is slightly smaller than that of the pristine MASnI3 surface. The energy barriers of water molecules diffusing through MASnI3 surfaces are relatively low, but when a water molecule penetrates the graphene sheet into the interior of the MASnI3 it has to overcome an energy barrier of as high as 9 eV. It is found that the water diffusions through the surfaces cause very severe damage to the structures of the graphene sheet and MASnI3 surface. So, the graphene can block the penetration of water into the inside of the material and retard the degradation of the perovskites. Coating a graphene sheet onto the MASnI3 surface to form a heterojunction is an effective strategy of enhancing the stability and performance of perovskite solar cells. This study could provide an in-depth understanding of the properties of graphene/MASnI3 heterojunctions and contribute to the design strategy of perovskite-based solar cells.

Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO2 Me) by Cp2 TaH3.

The elementometalation process is a fundamental chemical step in several catalytic cycles. In this work, density functional theory computations have elucidated the detailed elementometalation mechanism of activated alkyne RCCR(RCO2 Me) by Cp2 TaH3 and rationalized the selectivity in experimental findings. The calculated results show that in the formation process of (E)-olefin monohydride((E)-Pro), the Gibbs free energy barrier is low and the entire reaction is spontaneous and exothermic; thus, (E)-Pro can be formed easily. The formation of (Z)-η2 -olefin monohydride complex ((Z)-Pro) is difficult due to its high Gibbs free energy barrier. The formation process (E)-Pro consists of the following five steps: hydride H1-shift, conformational isomerism 1, hydride H2-shift, conformational isomerism 2, and olefin coordination process. Topological analysis shows that there is a five-membered ring plane structure in the reaction pathway and that the final product (E)-Pro belongs to a typical η2 -olefin monohydride complex. Our calculated results provide an explanation for experimental observations and useful insights for further development of olefin functionalization. © 2019 Wiley Periodicals, Inc.