Advances in PNP-ligated rare-earth-metal complexes: Reactivity and catalytic performances

Due to the large ionic radius and high electro-positivity nature, rare earth metal complexes are difficult to stabilize and undergo pathways like ligand redistribution and intramolecular C-H activation. To solve such problems and retain reactive versatility, rare earth complexes supported by a variety of tridentate PNP pincer ligands have been explored. Such complexes can serve as perfect precursors for preparing ultra-active rare earth species containing two metal-carbon bands, let alone Ln=N and Ln=P multiple bonds. In addition, the combined stability and activity of the cation rare earth mediates made them the best catalysts for the polymerization of olefins and other non-polar hydrocarbon monomers, especially conjugated dienes. The practical utilization of rare earth metal catalysts for new materials production have also extensively explored by experts from the academic and industries

Some catalytic and stoichiometric reactions of titanocene and chiral ansa-titanocene derivatives with silanes and siloxanes

Several types of catalytic and stoichiometric reactions of titanocenes and chiral ansa-titanocenes were studied.Dimethyltitanocene (DMT) and rac- (EBTHI) TiMe$sb2$ (EBTHI = ethylene-1,2-bis (4,5,6,7-tetrahydro-1-indenyl)) are effective catalyst precursors for hydrosilation of a variety of ketones when using in conjunction with secondary silanes. A catalyst generated by in situ reaction of enantiomerically pure S- (EBTHI) TiX$sb2$ (X = Cl, 1/2(S-1,1$sp prime$-binaphthyl-2,2$sp prime$-diolate)) with MeLi catalyzes hydrosilation of dialkyl ketones to give, after hydrolysis, the enantioenriched secondary alcohols in up to 70% ee. This result compares favorably with the best chiral-phosphine/Rh catalysts for asymmetric hydrosilation of dialkyl ketones. DMT and rac-(EBTHI) TiMe$sb2$ are also very active catalyst precursors for cross dehydrocoupling/co-intramolecular hydrosilation of allylic and homoallylic alcohols with secondary silanes. This is the first time such reactions catalyzed by group 4 metallocenes have been reported.Photochemical stoichiometric reactions of DMT and rac-(EBTHI) TiMe$sb2$ with hydrosiloxanes in the presence of pyridine produce two novel Ti(III)-pyridine complexes Cp$sb2$Ti(Me)(Py) and rac-(EBTHI) Ti(Me)(Py). Their structures were characterized by X-ray crystallography and EPR spectroscopy. Stoichiometric reaction of rac-(EBTHI) TiMe$sb2$ with phenylmethylsilane gives a Ti(III) hydride dimer, rac-((EBTHI)Ti($mu$-H)) $sb2$, which is the first structurally characterized Ti(III) hydride dimer without a bridging organic ligand. EPR spectroscopic study revealed that the dimer exists in equilibrium with its monomer in solution. Reaction of this hydride dimer in the presence of excess phenylphosphine produces a Ti(IV) diphosphanediyl complex, rac-(EBTHI) Ti(PPh)$sb2$, in quantitative yield. The structure of rac-(EBTHI) Ti(PPh)$sb2$ was also characterized by X-ray crystallography

Preface [to New Material and Chemical Industry, Proceedings of the Sixth International Conference on New Material and Chemical Industry]

[Excerpt] The Sixth International Conference on New Material and Chemical Industry (NMCI2021) was scheduled to be held in Sanya, China. Due to the COVID-19 pandemic, the meeting had to be changed from onsite to online during November 13-14, 2021 for academic exchanges & discussions. Three sessions were included: keynote speeches, oral presentations and poster presentations, covering a wide range of materials science and chemical industry, details about the presentations can be found in the Conference Overview part. [...

Study on the Hydraulic Characteristics of an Eccentric Tapering Outlet Pressure Box Culvert in a Pumping Station

The outlet pressure box culvert is often used as the drainage building of a pumping station. Because of its compact structure, it produces transverse flow velocity and then forms poor flow patterns, such as bias flow, reflux, and flow separation, which affect the discharge efficiency of the pumping station. Based on the combination of a physical model test and numerical simulation, the hydraulic characteristics of an eccentric tapering outlet pressure box culvert were analyzed. Focusing on the poor flow pattern in the box culvert, different optimization schemes were proposed to adjust the flow pattern. The flow pattern, transverse velocity distribution ratio (which represents the proportion of transverse velocity in velocity), average angle of the axial velocity, axial velocity uniformity, and pressure distribution of each scheme were compared to obtain the best scheme. The results show that the combination scheme of “diversion pier position and angle with deflecting flow baseplate” has the best optimization effect on the flow pattern. This scheme can effectively improve the bad flow pattern, significantly reduce the transverse velocity distribution ratio, and make the pressure distribution on both sides of the long diversion pier uniform. The axial velocity uniformity was increased by 17.45%, and the average angle of the axial velocity was increased by 8.23°

Development and validation of a nomogram for predicting recurrence-free survival in endometrial cancer: a multicenter study

Abstract Recurrence is the main cause of death in patients with endometrial cancer (EC). This study aimed to construct and validate a nomogram to predict the recurrence-free survival of patients with EC. This was a multicenter retrospective study. A total of 812 patients from Wuhan Tongji Hospital were divided into training and validation cohorts, and 347 and 580 patients from People’s Hospital of Peking University and Qilu Hospital of Shandong, respectively, were used for validation. Univariate and multivariate Cox regression analyses were used to construct a nomogram for predicting recurrence-free survival of EC. Calibration curves, receiver operating characteristic (ROC) curves, and consistency indexes (C-indexes) were used to estimate the performance of the model. Decision curve analysis (DCA) curves were used to assess the clinical utility of the model. Age (P = 0.013), cancer antigen 125 level (P = 0.014), lymphovascular space invasion (P = 0.004), International Federation of Gynecology and Obstetrics stage (P = 0.034), and P53 (P < 0.001) were independently associated with recurrence, and we constructed a nomogram based on these variables. The C-indexes of the validation cohorts were 0.880, 0.835, and 0.875, respectively. The calibration, ROC, and DCA curves revealed that this model had excellent performance and clinical utility. Combining clinical data, clinicopathological factors, serological indicators, and immunohistochemical marks, a multicenter externally verified nomogram with robust performance was constructed to predict the recurrence of patients with EC

Advances in Catalytic C–F Bond Activation and Transformation of Aromatic Fluorides

The activation and transformation of C–F bonds in fluoro-aromatics is a highly desirable process in organic chemistry. It provides synthetic methods/protocols for the generation of organic compounds possessing single or multiple C–F bonds, and effective catalytic systems for further study of the activation mode of inert chemical bonds. Due to the high polarity of the C–F bond and it having the highest bond energy in organics, C–F activation often faces considerable academic challenges. In this mini-review, the important research achievements in the activation and transformation of aromatic C–F bond, catalyzed by transition metal and metal-free systems, are presented

Strong and tunable magnetoelectric coupling in 2D trilayer heterostructures

The quest for electric-field control of nanoscale magnetic states such as skyrmions, which would impact the field of spintronics, has led to a challenging search for multiferroic materials or structures with strong magnetoelectric coupling and efficient electric-field control. Here we report a theoretical prediction that such phenomena can be realized in two-dimensional (2D) bilayer FE/PMM and trilayer FE/PMM/FE heterostructures (two-terminal and three-terminal devices), where FE is a 2D ferroelectric and PMM is a polar magnetic metal with strong spin-orbit coupling. Such a PMM has strong Dzyaloshinskii-Moriya interactions (DMI) that can generate skyrmions, while the FE can generate strong magnetoelectric coupling through polarization-polarization interactions. In trilayer heterostructures, contact to the metallic PMM layer enables multiple polarization configurations for electric-field control of skyrmions. We report density-functional-theory calculations for particular material choices that demonstrate the effectiveness of these arrangements, with the key driver being the polarization-polarization interactions between the PMM and FE layers. The present findings provide a method to achieve strong magnetoelectric coupling in the 2D limit and a new perspective for the design of related spintronics

PNP-Ligated Rare-Earth Metal Catalysts for Efficient Polymerization of Isoprene

The tridentate PNP ligand-supported rare-earth metal complexes, i.e., bis[o-diphenylphosphinophenyl]amido-Re-bis[o-dimethylaminobenzyl], [(Ph2P-o-C6H4)2N]Re[(CH2-o-Me2N(C6H4))2]: (Re = Y, 1; Nd, 2; Gd, 3) were applied to isoprene polymerization. When activated with borate activator ([PhMe2NH][B(C6F5)4] (NH-BARF), catalysts 1 and 3 exhibited excellent catalytic efficiency in aromatic media, produced very-high to ultrahigh molecular weight (Mw over 130 × 104 g/moL) polyisoprene rubber (PIR), and the obtained PIR contained over 98% cis-1,4 head-to-tail repeating unites. In most cases, the borate-activated polymerization reaction proceeded in a quasi-living pattern (PDI = 1.2–1.5) under controlled monomer conversion; whereas, activated with the commercially available modified methylaluminoxane (MMAO3A) in aliphatic hydrocarbon media, complexes 1, 2 and 3 all showed high catalytic efficiency, produced high molecular weight PIR with narrow molecular weight distribution (PDI ≤ 2.0) and high cis-1,4 head-to tail repeating unites in the range of 91–95%. Thus, the catalyst systems that consisted of 1, 2 and 3/MMAO3A, are closely relevant to the current industrial polybutadiene rubber (PBR) and PIR production processes