Synthesis of Phosphorus(V)-Stabilized Geminal Dianions. The Cases of Mixed P═X/P→BH3 (X = S, O) and P═S/SiMe3 Derivatives

Synthesis and reactivity of alkali metal aluminates bearing bis(organoamido)phosphane ligand

In this study, we report a group of alkali metal aluminates bearing bis(organoamido)phosphane ligand. The starting complex {[PhP(NtBu)2]AlMe2}Li·OEt2 (1) was prepared by stepwise deprotonation of the parent PhP(NHtBu)2 by nBuLi and AlMe3. Further derivatization of aluminate 1 was performed by the virtual substitution of lithium -{[PhP(NtBu)2]AlMe2}K (2), methyl substituents - {[PhP(NtBu)2]AlH2}Li·THF (3), modification of steric bulk and induction effects on the phosphorus atom - {[tBuP(N-2,6-iPr2C6H3)2]AlMe2}Li·(OEt2)2 (4), and phosphorus atom oxidation state {[Ph(Y)P(NtBu)2]AlMe2}Li (Y = O (5), S (6), Se (7), Te (8)). The structure causing non-covalent interactions in 1-4 were evaluated with the help of theoretical calculations and topological analysis ranging from π-electron system-metal to agostic interactions of various types. The further reactions of 1 with various nucleophiles were found to be a versatile tool for the preparation of iminophosphonamides via the formation of P-E bond (E = Si, Ge, Sn, Pb, P, and C) and followed by P(III) → P(V) tautomeric shift.

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and 6Li/13C NMR spectroscopic data

Dilithio sulfonyl methandiides are a synthetically and structurally highly interesting group of functionalized geminal dianions. Although very desirable, knowledge of the structure of dilithio methandiides in solution was lacking up to now. Herein, we describe the isolation and determination of the structure of tetrameric dilithio (trimethylsilyl)(phenylsulfonyl) methandiide in solution and in the crystal. The elucidation of the structure of the tetramer is based on crystal structure analysis and ¹³C/⁶Li NMR spectroscopic data. A characteristic feature of the structure of the tetramer is the C₂ symmetric C–Li chain, composed of four doubly Li-coordinated dianionic carbon and five Li atoms. Three Li atoms are devoid of a contact to a dianionic C atom. The tetramer, the dianionic C atoms of which undergo fast exchange, is in THF solution in fast equilibrium with a further aggregate, which is stable only at low temperatures.

Designing of a Phosphorus, Nitrogen, and Sulfur Three-Flame Retardant Applied in a Gel Poly-m-phenyleneisophthalamide Nanofiber Membrane for Advanced Safety Lithium-Sulfur Batteries

Based on the urgent demand of non-flammable electrospun nanofiber separators and the strong adsorption to polysulfides through chemical doping in separators for Li-S cell, in this study, a phosphorus, nitrogen, and sulfur three-flame retardant (di-(2-(5,5-dimethyl-2-sulfido-1,3,2-dioxaphosphinan-2-yl)hydrazineyl)-P-ethylphosphinic) was synthesized and a high-performance flame-retarding poly-m-phenyleneisophthalamide (PMIA) membrane was successfully prepared through blend electrospinning with the flame retardant, it is regarded as a promising gel nanofiber membrane with advanced safety for the lithium-sulfur (Li-S) cell, and it was systematically explored and analyzed. It was presented that the modified PMIA electrospun membrane with the synthesized flame retardant possessed excellent flame retardation, outstanding thermal stability, and good mechanical strength. Meanwhile, the prepared membrane showed extraordinarily high uptake and preserving retention of the liquid electrolyte and enhanced ionic conductivity. More importantly, the assembled Li-S cells using the obtained membrane exhibited excellent cycling retention and outstanding rate capability because of its fast ion transportation and good interfacial compatibility. The assembled batteries with the novel membrane exhibited a high first-cycle discharge capacity of 1121.50 mA h g^-1, superior discharge capacity retention of 713.41 mA h g^-1, and high Coulombic efficiency of 98.46% after 600 cycles at the 0.5 C rate. In addition, the limiting oxygen index of the obtained nanofiber membrane with flame retardancy was as high as ∼30.0%, which could greatly enhance the safety of the electrospun nanofiber separator. The excellent electrochemical performances and safety for the battery assembled with the prepared gel PMIA nanofiber membrane were attributed to the significantly prevented "shuttle effect" of lithium polysulfides based on the physical capturing of lithium polysulfides through the obtained jelly-like gel state and chemical binding of polysulfide intermediates through the tridoped phosphorus, nitrogen, and sulfur elements in the PMIA and the flame retardant. All of these excellent properties will promote the great development of the Li-S battery with high performance and satisfactory safety.

Geminal Dianions Stabilized by Main Group Elements

This review is dedicated to the chemistry of stable and isolable species that bear two lone pairs at the same C center, i.e., geminal dianions, stabilized by main group elements. Three cases can thus be considered: the geminal-dilithio derivative, for which the two substituents at C are neutral, the yldiide derivatives, for which one substituent is neutral while the other is charged, and finally the geminal bisylides, for which the two substituents are positively charged. In this review, the syntheses and electronic structures of the geminal dianions are presented, followed by the studies dedicated to their reactivity toward organic substrates and finally to their coordination chemistry and applications.

Instability of metal 1,3-benzodi(thiophosphinoyl)methandiide complexes: formation of hafnium, tin and zirconium complexes of 1,3-benzodi(thiophosphinoyl)thioketone dianionic ligand [1,3-C6H4(PhPS)2CS]2−

The reaction illustrates that the metal centre and ligand substituents are crucial for the stabilization of a C_methandiideHf bond.

Substitution effects on the formation of T-shaped palladium carbene and thioketone complexes from Li/Cl carbenoids

The preparation of palladium thioketone and T-shaped carbene complexes by treatment of thiophosphoryl substituted Li/Cl carbenoids with a Pd(0) precursor is reported. Depending on the steric demand, the anion-stabilizing ability of the silyl moiety (by negative hyperconjugation effects) and the remaining negative charge at the carbenic carbon atom, isolation of a three-coordinate, T-shaped palladium carbene complex is possible. In contrast, insufficient charge stabilization results in the transfer of the sulfur of the thiophosphoryl moiety and thus in the formation of a thioketone complex. While the thioketones are stable compounds the carbene complexes are revealed to be highly reactive and decompose under elimination of Pd metal. Computational studies revealed that both complexes are formed by a substitution mechanism. While the ketone turned out to be the thermodynamically favored product, the carbene is kinetically favored and thus preferentially formed at low reaction temperatures.

Synthesis and bonding in carbene complexes of an unsymmetrical dilithio methandiide: a combined experimental and theoretical study

Herein, we report the preparation of a new unsymmetrical, bis(thiophosphinoyl)-substituted dilithio methandiide and its application for the synthesis of zirconium- and palladium-carbene complexes. These complexes were found to exhibit remarkably shielded (13)C NMR shifts, which are much more highfield-shifted than those of "normal" carbene complexes. DFT calculations were performed to determine the origin of these observations and to distinguish the electronic structure of these and related carbene complexes compared with the classical Fischer and Schrock-type complexes. Various methods show that these systems are best described as highly polarized Schrock-type complexes, in which the metal-carbon bond possesses more electrostatic contributions than in the prototype Schrock systems, or even as "masked" methandiides. As such, geminal dianions represent a kind of "extreme" Schrock-type ligands favoring the ionic resonance structure M(+)-CR2(-) as often used in textbooks to explain the nucleophilic nature of Schrock complexes.