Synthesis of Bench-stable Polycyclic Organophosphorus Heterocycles via Staudinger-type Annulations of ortho-Azidophenols.

The formation of a five- or six-membered ring is known to stabilize unstable molecular structures such as hemiacetals. This idea can also be extended to stabilize other high-coordinated p-block element species. Herein, we synthesized two novel polycyclic organophosphorus heterocycles via Staudinger-type annulations. Reactions of either ortho-phosphinoarenesulfonyl fluorides 1 or ortho-phosphinobenzoic acid methyl esters 4 with ortho-azidophenols 2 gave rise to penta-coordinated P(V) heterocycles, benzo-benzo-1,2,3-thiazaphospholo-1,3,2-oxazaphosphole (B-B-TAP-OAP) 3 and benzo-benzo-1,2-azaphospholo-1,3,2-oxazaphosphol-12-one (B-B-AP-OAP) 5 in satisfactory yields. It is remarkable that heterocycles 3 and 5 are both bench-stable and exhibit considerable stability in a 10 % aqueous tetrahydrofuran solution. Preliminary computational studies disclosed that the formation of nitrogen gas is the key driving force for the annulations. In addition, the formation of a strong Si-F bond is another contributor to the annulation of 1 and 2.

A space-confined strategy towards stable α/ß-Bi2O3 heterojunction anode for high-energy aqueous battery.

It is very necessary to design a high-capacity and stable Bi2O3 anode for nickel-bismuth (Ni//Bi) batteries. In this work, a stable α- and ß- phase Bi2O3 heterojunction nanocomposite (α/ß - Bi2O3) was successfully prepared via a simple "space-confined" strategy and it was used as a superior anode for nickel-bismuth (Ni//Bi) battery. The α/ß-Bi2O3 obtained by using MCM-41 as a space-confined template possesses a stable structure and enhanced charge transfer capability. Such superior traits vest the designed α/ß-Bi2O3 electrode with high specific capacity (235 mAh g-1 at 1 A g-1), extraordinary rate performance (137 mAh g-1 at 40 A g-1, and ∼58% capacity retention vs 1 A g-1), and excellent cyclic durability (75% capacity retention after 5000 cycles). Such performances are far superior to that of mono-phase α-Bi2O3 and ß-Bi2O3 electrodes. Furthermore, an excellent Ni//Bi battery with outstanding energy density (∼155 Wh kg-1) and long cycle life was assembled using the obtained α/ß-Bi2O3 electrode and a NiC2O4 electrode as anode and cathode, respectively (NiC2O4//α/ß-Bi2O3). This work opens a new alternative strategy for the rational design of efficient electrodes for reliable aqueous rechargeable batteries.

Tertiary Amine-Mediated Reductions of Phosphine Oxides to Phosphines.

The reduction of phosphine oxides without the use of highly reactive reductants represents a safer and more sustainable solution for recycling of organophosphorus compounds. Herein, we disclose an N,N,N',N'-tetramethylethylenediamine (TMEDA)-mediated reduction via an unusual intermolecular hydride transfer. Mechanistic studies suggest that TMEDA serves as a hydride donor, while the P(V) halophosphonium salt acts as the hydride acceptor. This methodology provides a scalable and efficient protocol to reduce phosphine oxides under mild conditions.

An Innovative Bi12 SiO20 Multistage Cubic Nanospheres Cathode for High-Performance Bi//Zn Battery.

Alkaline Bi//Zn batteries with superb safety, low cost, and high power density are promising candidates for large-scale electrical energy storage. However, their developments are severely limited by the Bi-based cathode as the unsatisfying capacity and cycle life. Herein, an innovative multistage cubic nanospheres Bi12 SiO20 (MCS-Bi12 SiO20 ) is successfully synthesized by a simple calcination method, which shows excellent energy storage performances of superior specific capacity (294 mAh g-1 at 0.5 A g-1 ) and outstanding rate capability (134 mAh g-1 at 12 A g-1 ). When coupled with Zn anode a superior MCS-Bi12 SiO20 //Zn is fabricated, which delivers a high energy density of 247.5 Wh kg-1 at the power density of 375 W kg-1 . Additionally, the MCS-Bi12 SiO20 //Zn battery shows excellent cycle life, which reserves more than 100 % of its original capacity after 5000 cycles. Such performance is higher than previously reported Bi//Zn battery and most other Zn batteries. This is the first example of using Bi12 SiO20 as cathode for RAZBs, which may provide highly promising material towards better Bi//Zn battery.

Ortho-Phosphinoarenesulfonamide-Mediated Staudinger Reduction of Aryl and Alkyl Azides.

Conventional Staudinger reductions of organic azides are sluggish with aryl or bulky aliphatic azides. In addition, Staudinger reduction usually requires a large excess of water to promote the decomposition of the aza-ylide intermediate into phosphine oxide and amine products. To overcome the challenges above, we designed a novel triaryl phosphine reagent 2c with an ortho-SO2NH2 substituent. Herein, we report that such phosphine reagents are able to mediate the Staudinger reduction of both aryl and alkyl azides in either anhydrous or wet solvents. Good to excellent yields were obtained in all cases (even at a diluted concentration of 0.01 M). The formation of B-TAP, a cyclic aza-ylide, instead of phosphine oxide, eliminates the requirement of water in the Staudinger reduction. In addition, computational studies disclose that the intramolecular protonation of the aza-ylide by the ortho-SO2NH2 group is kinetically favorable and responsible for the acceleration of Staudinger reduction of the aryl azides.

Construction of Benzo-1,2,3-thiazaphosphole Heterocycles by Annulations of ortho-Phosphinoarenesulfonyl Fluorides with Trimethylsilyl Azide.

Annulations of ortho-phosphinoarenesulfonyl fluorides with trimethylsilyl azide were developed to access an unprecedented benzo-1,2,3-thiazaphosphole heterocycle. A corresponding reaction mechanism was proposed and further elucidated by experimental and computational studies. The reaction proceeds through a Staudinger-type iminophosphorane intermediate followed by intramolecular trapping with sulfonyl fluoride.

Structural and defect engineering of cobaltosic oxide nanoarchitectures as an ultrahigh energy density and super durable cathode for Zn-based batteries.

The key challenges of aqueous Zn-based batteries (ZBBs) are their unsatisfactory energy density and poor lifespan, mainly arising from the low capacity and irreversibility of the cathode materials. Herein, a three-dimensional (3D) ordered mesoporous nanoarchitecture cobaltosic oxide (M-Co3O4) with rich oxygen vacancies (M-Co3O4-x ) is reported as a new promising advanced cathode material for rechargeable ZBBs. The experimental results and DFT calculations reveal that the energy storage capacity is significantly enhanced by the synergistic effect of mesopores and oxygen vacancies. Benefiting from the merits of a substantially fast ion diffusion channel, high electrical conductivity, large active surface area, strong OH- adsorption capacity and stable structure, the fabricated M-Co3O4-x //Zn battery delivers a remarkable capacity of 384 mA h g-1 at 1.0 A g-1 which even rises up to 420 mA h g-1 after cycling activation with an ultrahigh energy density of 722.4 W h kg-1 (based on the weights of the cathode active material), which outperforms most of the previously reported aqueous ZBBs. More impressively, the M-Co3O4-x //Zn battery exhibits extraordinary cycling stability, both at 1 A g-1 and 10 A g-1 without any decay of capacity after 6000 and 60 000 cycles, respectively, and such high cycling stability is reported for the first time in ZBBs. The ultrahigh energy and superlong lifespan of aqueous ZBBs could make it satisfy some practical energy demands.