过渡金属卡宾正离子的从头算研究

过渡金属卡宾正离子被认为是如烯烃的聚合和烷基金属的分解过程等许多反应的中间体．较为稳定的环丁烷金属离子和环戊烷金属离子已从相应酮的脱羰反应获得［１］．Ｊａｃｏｂｓｏｎ等［２］研究了ＦｅＣＨ＋２和ＣｏＣＨ＋２与烯烃和环烷烃的气相反应．Ｍｃｋｅｅ［３］在...     

Valence Isomerization of a 1,3-Diphosphacyclobutane-2,4-diyl: Photochemical Ring Closure to 2,4-diphosphabicyclo[1.1.0]butane and Its Thermal Ring Opening to gauche-1,4-Diphosphabutadiene

The bond stretch isomer 1,3-diphosphacyclobutane-2,4-diyl 1 was transformed photochemically to give the previously unknown 2,4-diphosphabicyclo[1.1.0]butane 2 , which itself can be converted thermally into gauche-1,4-diphosphabutadiene 3 . The crystal structures of these three energy-rich valence isomers of 1,2-diphosphete have been determined. R=SiMe₃; Mes*=2,4,6-tBu₃C₆H₂.     

Unusual Stability despite a P‐bonded Proton: Phospha and Diphospha Ureas with the TrtP(H)‐Moiety

As the first diphospha‐urea with P‐bonded protons, [TrtP(H)]₂C=O ( 3 ) was found to be of amazing stability, which is thought to be due to the presence of the triphenylmethyl groups. Unlike known cyclic or non‐cyclic analogues, 3 showed next to no tendency to eliminate carbon monoxide. 3 was obtained by reaction of the dimeric phospha‐isocyanate (TrtPCO)₂ ( 1 ) with LiAlH₄, in which the intermediary phosphaalkene 2 was observed. Caused by its two asymmetric phosphorus atoms, 3 appeared as a mixture of two isomers, meso‐3 and rac‐3 (ratio: 20 : 1). Theoretical considerations, and the analysis of the proton‐coupled ³¹P NMR spectrum (spin system: AA′XX′), allowed the assignment of the signals to the two isomers. The action of anhydrous hydrogen chloride on 3 led to the cleavage of one P–C(:O)‐bond, and formation of an equimolar mixture of TrtPH₂ ( 5 ) and TrtP(H)C(:O)Cl ( 6 ). Cleavage of a P–C(:O)‐bond in 3 was also observed in its reaction with tetramethylguanidine (TMG) or ammonia. As proved by ³¹P NMR spectroscopy in the case of TMG, the reaction proceeded via the phosphaalkene intermediate 8 . Acting as nucleophiles, TMG and ammonia substituted TrtP(H) in 3 , and the P,N‐ureas 9 and 10 , with TrtPH₂ ( 5 ) as a side product, were obtained.     

Synthese und Struktur eines 1,5-Diphospha-2,3,4,6,7,8hexasilabicyclo[3.2.1]octans mit einem neuen Cyclosilaphosphangerüst

Synthesis and Structure of a 1,5-Diphospha-2,3,4,6,7,8-hexasilabicyclo[3.2.1]octane with an New Cyclosilaphosphane Skeleton The reaction of tert-butyl-tris(chlorodimethylsilyl)silane 1 with three mole-equiv. [LiPH₂(dme)] in THF from –40 to 25 °C surprisingly furnishes the novel bicyclic cyclosilaphosphane 3 , which has been isolated in the form of colorless crystals in 29% yield. The practically unstrained Si₆P₂ skeleton in 3 is a constitutional isomer of the higher symmetric 1,4-Diphospha-2,3,5,6,7,8-hexasilabicyclo[2.2.2]octane. Multinuclear-NMR spectroscopic investigations and a single-crystal structure analysis prove the constitution of 3 . Whereas the Si–P distances are without peculiarity, the Si–Si distances in the Si₂ and Si₃ bridges are significantly different. This can be explained by different magnitudes of through bond interactions between the n-orbitals at phosphorus and the σ* acceptor orbitals of the Si–Si bonds which depend on the bridge lengths and are in analogy to the electronic features observed in 1,4-diphospha-2,3,5,6,7,8-hexasilabicyclo[2.2.2]octane.     

Common Features in the Crystal Structures of the Compounds Bis(dimethylstibanyl)oxane and ‐sulfane,and the Minerals Valentinite and Stibnite (Grauspießglanz)

Bis(dimethylstibanyl)oxane ( 1 ) and ‐sulfane ( 2 ), the two simplest organoelement species with an Sb–E–Sb fragment (E = O, S), were prepared by alkaline hydrolysis of bromodimethylstibane and by oxidation of tetramethyldistibane with sulfur [18], respectively. As shown by an x‐ray structure analysis of compound 1 (m. p. < –20 °C; P2₁2₁2₁, a = 675.9(2), b = 803.1(2), c = 1666.8(4) pm at –70 ± 2 °C; Z = 4; R1 = 0.042), the molecules (O–Sb 198.8 and 209.9 pm, Sb–O–Sb 123.0°) adopt a syn‐anti conformation in the solid state and are arranged in zigzag chains along [010] via weak intermolecular O‥Sb interactions (258.5 pm, Sb–O‥Sb 117.8°, O‥Sb–O 173.5°) making use, however, of only one Me₂Sb moiety. Primary and secondary bond lengths and angles agree very well with corresponding values published for valentinite, the orthorhombic modification of antimony(III) oxide [3]. Bis(dimethylstibanyl)sulfane ( 2 ) (m. p. 29 to 31 °C) crystallizes in the uncommon space group P6₅22 (a = 927.8(3), c = 1940.9(7) pm at –100 ± 2 °C; Z = 6; R1 = 0.021). Owing to coordination numbers of (1 + 1) and (2 + 2) for both Me₂Sb groups and the sulfur atom, respectively, molecules with an approximate syn‐syn conformation (S–Sb 249.8 pm, Sb–S–Sb 92.35°) build up a three‐dimensional net of double helices which are linked together by Sb‥S contacts (316.4 pm). These parameters shed more light onto the rather complicated structure and bonding situation in stibnite (antimony(III) sulfide [4]). The molecular packing of compound 2 is compared with the structures of relevant inorganic solids, especially with that of β‐quartz [37].     

Synergetic Coupling of Redox-Active Sites on Organic Electrode Material for Robust and High-Performance Sodium-Ion Storage

Organic electrode materials (OEMs), valued for their sustainability and structural tunability, have been attracting increasing attention for wide application in sodium-ion batteries (SIBs) and other rechargeable batteries. However, most OEMs are plagued with insufficient specific capacity or poor cycling stability. Therefore, it′s imperative to enhance their specific capacity and cycling stability through molecular design. Herein, we designed and synthesized a heteroaromatic molecule 2,3,8,9,14,15-hexanol hexaazatrinaphthalene (HATN-6OH) by the synergetic coupling of catechol (the precursor of ortho-quinone)/ortho-quinone functional groups and HATN conjugated core structures. The abundance of catechol/ortho-quinone and imine redox-active moieties delivers a high specific capacity of nine-electron transfer for SIBs. Most notably, the π–π interactions and intermolecular hydrogen bond forces among HATN-6OH molecules secure the stable long-term cycling performance of SIBs. Consequently, the as-prepared HATN-6OH electrode exhibited a high specific capacity (554 mAh g⁻¹ at 0.1 A g⁻¹), excellent rate capability (202 mAh g⁻¹ at 10 A g⁻¹), and stable long-term cycling performance (73 % after 3000 cycles at 10 A g⁻¹) in SIBs. Additionally, the nine-electron transfer mechanism is confirmed by systematic density functional theory (DFT) calculation, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and Raman analysis. The achievement of the synergetic coupling of the redox-active sites on OEMs could be an important key to the enhancement of SIBs and other metal-ion batteries.     

Organoboron Reagent-Controlled Selective (Deutero)Hydrodefluorination

(Deuterium-labeled) CF₂H- and CFH₂-moieties are of high interest in drug discovery. The high demand for the incorporation of these fluoroalkyl moieties into molecular structures has witnessed significant synthetic progress, particularly in the (deutero)hydrodefluorination of CF₃-containing compounds. However, the controllable replacement of fluorine atoms while maintaining high chemoselectivity remains challenging. Herein, we describe the development of a selective (deutero)hydrodefluorination reaction via electrolysis. The reaction exhibits a remarkable chemoselectivity control, which is enabled by the addition of different organoboron sources. The procedure is operationally simple and scalable, and provides access in one step to high-value building blocks for application in medicinal chemistry. Furthermore, density functional theory (DFT) calculations have been carried out to investigate the reaction mechanism and to rationalize the chemoselectivity observed.     

C60正丙胺铂,铑配合物的合成及其催化硅氢化性能

Ｃ６０与正丙胺反应,然后分别与氯亚铂酸钾或三氯化铑配合,制得出含配位氮原子的富勒烯铂,铑 配合物,它们均能有效地催化烯烃与三乙氧基硅烷硅氢加成,铂配合物还对苯乙烯有独特的催化性能,以近１００％的区域选择性得到α－加成产物,对催化机理进行了初步的探讨。     

Complexes Featuring a cis-[M U M] Core (M=Rh,Ir): A New Route to Uranium-Metal Multiple Bonds

Although examples of multiple bonds between actinide elements and main-group elements are quite common, studies of the multiple bonds between actinide elements and transition metals are extremely rare owing to difficulties associated with their synthesis. Here we report the first example of molecular uranium complexes featuring a cis-[M U M] core (M=Rh, Ir), which exhibits an unprecedented arrangement of two M U double dative bond linkages to a single U center. These complexes were prepared by the reactions of chlorine-bridged heterometallic complexes [{U{N(CH₃)(CH₂CH₂NPⁱPr₂)₂}(Cl)₂[(μ-Cl)M(COD)]₂}] (M=Rh, Ir) with MeMgBr or MeLi, a new method for the construction of species with U−M multiple bonds. Theoretical calculations including dispersion confirmed the presence of two U M double dative bonds in these complexes. This study not only enriches the U M multiple bond chemistry, but also provides a new opportunity to explore the bonding of actinide elements.