Exploration of Solid-State vs Solution-State Structure in Contact Ion Pair Systems: Synthesis, Characterization, and Solution-State Dynamics of Zinc Diphenyl Phosphate, [Zn{O2P(OPh)2}2], Donor-Base-Supported Complexes

A family of zinc phosphate complexes supported by nitrogen donor-base ligands have been synthesized, and their molecular structures were identified in both the solid (X-ray crystallography) and solution state (DOSY NMR spectroscopy). [Zn{O₂P(OPh)₂}₂]_∞ (1), formed from the reaction of Zn[N(SiMe₃)₂]₂ with HO(O)P(OPh)₂ coordinates to donor-base ligands, i.e., pyridine (Py), 4-methylpyridine (4-MePy), 2,2-bipyridine (bipy), tetramethylethylenediamine (TMEDA), pentamethyldiethylenetriamine (PMDETA), and 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me₃-TAC), to produce polymeric 1D structures, [(Py)₂Zn{O₂P(OPh)₂}₂]_∞ (2) and [(4-MePy)₂Zn{O₂P(OPh)₂}₂]_∞ (3), the bimetalic systems, [(Bipy)Zn{O₂P(OPh)₂}₂]₂ (4), [(TMEDA)Zn{O₂P(OPh)₂}₂]₂ (5), and [(Me₃-TAC)Zn{O₂P(OPh)₂}₂]₂ (7), as well as a mono-nuclear zinc bis-diphenylphosphate complex, [(PMDETA)Zn{O₂P(OPh)₂}₂] (6). ¹H NMR DOSY has been used to calculate averaged molecular weights of the species. Studies are consistent with the disassembly of polymeric 3 into the bimetallic species [(Me-Py)₂·Zn₂{O₂P(OPh)₂}₄], where the Me-Py ligand is in rapid exchange with free Me-Py in solution. Further ¹H DOSY NMR studies of 4 and 5 reveal that dissolution of the complex results in a monomer dimer equilibrium, i.e., [(Bipy)Zn{O₂P(OPh)₂}₂]₂ ⇆ 2[(Bipy)Zn{O₂P(OPh)₂}₂] and [(TMEDA)Zn{O₂P(OPh)₂}₂]₂ ⇆ 2[(TMEDA)Zn{O₂P(OPh)₂}₂], respectively, in which the equilibria lie toward formation of the monomer. As part of our studies, variable temperature ¹H DOSY experiments (223 to 313 K) were performed upon 5 in d₈-tol, which allowed us to approximate the enthalpy [ΔH = -43.2 kJ mol^-1 (±3.79)], entropy [ΔS = 109 J mol^-1 K^-1 (±13.9)], and approximate Gibbs free energy [ΔG = 75.6 kJ mol^-1 (±5.62) at 293 K)] of monomer-dimer equilibria. While complex 6 is shown to maintain its monomeric solid-state structure, ¹H DOSY experiments of 7 at 298 K reveal two separate normalized diffusion coefficients consistent with the presence of the bimetallic species [(TAC)_2-xZn₂{O₂P(OPh)₂}₄], (x = 1 or 0) and free TAC ligand.

Study of Lithium-Extraction Systems Based on Benzo-15-Crown-5 Ether and Alkylimidazolium-Based Ionic Liquid

The extraction of lithium from aqueous solutions of LiNTf₂ and LiCl salts using benzo-15-crown-5 ether (B15C5) as an extractant in [C8mim][NTf₂] ionic liquid was studied. The transition of the extractant into the aqueous phase and the distribution of Cl^- ions during lithium extraction from LiCl solutions were determined. LiNTf₂ complexes with B15C5 with different LiNTf₂:B15C5 ratios were isolated for the first time and characterized via X-ray diffraction and IR spectroscopy. Differences in the extraction process of LiCl and LiNTf₂ were determined via an infrared spectroscopic study of the extraction systems.

Fluorinated Poly-oxalate Electrolytes Stabilizing both Anode and Cathode Interfaces for All-Solid-State Li/NMC811 Batteries

The relatively narrow electrochemical steady window and low ionic conductivity are two critical challenges for Li⁺ -conducting solid polymer electrolytes (SPE). Here, a family of poly-oxalate(POE) structures were prepared as SPE; among them, POEs composed from diols with an odd number of carbons show higher ionic conductivity than those composed from diols with an even number of carbons, and the POE composed from propanediol (C5-POE) has the highest Li⁺ conductivity. The HOMO (highest occupied molecular orbital) electrons of POE were found located on the terminal units. When using trifluoroacetate as the terminating unit (POE-F), not only does the HOMO become more negative, but also the HOMO electrons shift to the middle oxalate units, improving the antioxidative capability. Furthermore, the interfacial compatibility across the Li-metal/POE-F is also improved by the generation of a LiF-based solid-electrolyte-interlayer(SEI). With the trifluoroacetate-terminated C5-POE (C5-POE-F) as the electrolyte and Li⁺ -conducting binder in the cathode, the all-solid-state Li/LiNi_0.8 Mn_0.1 Co_0.1 O₂ (NMC811) cells showed significantly improved stability than the counterpart with poly-ether, providing a promising candidate for the forthcoming all-solid-state high-voltage Li-metal batteries.

Tridentate Phosphine Ligands Bearing Aza-Crown Ether Lariats

Crown ethers are useful macrocycles that act as size-selective binding sites for alkali metals. These frameworks have been incorporated into a number of macromolecular assemblies that use simple cations as reporters and/or activity triggers. Incorporating crown ethers into secondary coordination sphere ligand frameworks for transition metal chemistry will lead to new potential methods for controlling bond formation steps, and routes that couple traditional ligand frameworks with these moieties are highly desirable. Herein we report the syntheses of a family of tridentate phosphine complexes bearing tethered aza-crown ethers (lariats) designed to modularize the variation of aza-crown size, lariat length, and distal phosphine substituents, followed by the synthesis and solid-state structures of Mo(III) complexes bearing cations in the pendent crown ethers.

Nickel complexes of a binucleating ligand derived from an SCS pincer

A new heterobimetallic complex contains Ni^II in an SCS pincer and lithium in an ether loop, bridged by bromide.

Elucidation of inorganic reaction mechanisms in ionic liquids: the important role of solvent donor and acceptor properties

In this article, we focus on the important role of solvent donor and acceptor properties of ionic liquids in the elucidation of inorganic reaction mechanisms. For this purpose, mechanistic and structural studies on typical inorganic reactions, performed in ionic liquids, have been conducted. The presented systems range from simple complex-formation and ligand-substitution reactions to the activation of small molecules by catalytically active complexes. The data obtained for the reactions in ionic liquids are compared with those for the same reactions carried out in conventional solvents, and are discussed with respect to the donor and acceptor properties of the applied ionic liquids. The intention of this perspective is to gain more insight into the role of ILs as solvents and their interaction with metal ions and complexes in solution.

Poly[bis-(acetonitrile-κN)bis-[μ(3)-bis(tri-fluoro-methane-sulfonyl)-imido-κO,O':O'':O''']dilithium]

In the title compound, [Li(2)(CF(3)SO(2)NSO(2)CF(3))(2)(CH(3)CN)(2)](n), two Li(+) cations reside on crystallographic inversion centers, each coordinated by six O atoms from bis(trifluoromethanesulfonyl)imide (TFSI(-)) anions. The third Li(+) cation on a general position is four-coordinated by two anion O atoms and two N atoms from acetonitrile mol-ecules in a tetra-hedral geometry.

Facile microwave-assisted synthesis of cyclic amidinium salts

The cyclization of N,N'-dialkyl or diaryl ethane-1,2-diamines or propane-1,3-diamines with inorganic ammonium salts and orthoesters proceeds briskly under microwave irradiation to afford the corresponding imidazolinium or tetrahydropyrimidinium salts. The transformation is highly versatile and tolerates a wide range of substituents and counterions. It could be scaled from 1 to 50 mmol without any difficulty. Because the workup is equally rapid and straightforward, this experimental procedure provides fast and convenient access to an important class of heterocyclic compounds that have found numerous applications as N-heterocyclic carbene precursors, organocatalysts, and ionic liquids.

The Initial Stages of Radiation Damage in Ionic Liquids and Ionic Liquid-Based Extraction Systems

Radical intermediates generated in radiolysis and photoionization of ionic liquids (ILs) composed of ammonium, phosphonium, pyrrolidinium, and imidazolium cations and bis(triflyl)amide, dicyanamide, and bis(oxalato)borate anions have been studied using magnetic resonance spectroscopy. Large yields of terminal and penultimate C-centered radicals are observed in the aliphatic chains of the phosphonium, ammonium, and pyrrolidinium cations, but not for imidazolium cation. This pattern is indicative of efficient deprotonation of a hole trapped on the parent cation (the radical dication) that competes with rapid electron transfer from a nearby anion. This charge transfer leads to the formation of stable N- or O-centered radicals; the dissociation of parent anions is a minor pathway. Addition of 10-40 wt % of trialkyl phosphate (a common extraction agent) has relatively little effect on the fragmentation of the ILs. The yield of the alkyl radical fragment generated by dissociative electron attachment to the trialkyl phosphate is <4% of the yield of the radical fragments derived from the IL solvent. The import of these observations for radiation stability of the prospective nuclear cycle extraction systems based upon the ILs is discussed.

Crystal Engineering in Ionic Liquids. The Crystal Structures of [Mppyr]3[NdI6] and [Bmpyr]4[NdI6][Tf2N]

Single crystals of [mppyr][NdI6] and [bmpyr][NdI6][Tf2N] are the first surprising examples of how the cation of an ionic liquid determines the compound formation from an ionic liquid. Depending upon the variation of the length of the alkyl chain of the quaternary pyrrolidinium cation (C3 and C4, respectively), incorporation of the anion of the ionic liquid, [Tf2N]-, can either be evoked or suppressed.

Homoleptic Alkaline Earth Metal Bis(trifluoromethanesulfonyl)imide Complex Compounds Obtained from an Ionic Liquid

The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+ cations to infinite (infinity)(1)[Ba(Tf2N)3] chains.

Synthesis of mono- and geminal dimetalated carbanions of bis(phenylsulfonyl)methane using alkali metal bases and structural comparisons with lithiated bis(phenylsulfonyl)imides

The alpha,alpha'-stabilized carbanion complexes [(PhSO2)2CHLi.THF]1, [(PhSO2)2CHNa.THF]2 and [(PhSO2)2CHK]3 were prepared by the direct deprotonation of bis(phenylsulfonyl)methane I in THF with one molar equivalent of MeLi, BuNa and BnK respectively. The geminal dianionic complexes [(PhSO2)2CLi2.THF]4, [(PhSO2)2CNa2.0.55THF]5 and [(PhSO2)2CK2]6 were similarly prepared by the reaction of I with two molar equivalents of MeLi, BuNa and BnK respectively in THF. NMR and MS solution studies of 1-3 are consistent with the formation of charge-separated species in DMSO media. Solutions studies of 4-6, in conjunction with trapping experiments, indicate that the dianions deprotonate DMSO and regenerate the monoanions 1-3. Crystallographic analysis of 1 revealed a 1D chain polymer in which the metal centers are chelated by the bis(sulfonyl) ligands and connect to neighboring units through Li-O(S) interactions. An unexpected feature of 1 is that the polymeric chains are homochiral, since the chelating ligands of the backbone adopt the same relative configuration. Also, the phenyl substituents of each chelate in 1 are oriented in a cisoid manner. The sodium derivative 2 adopts a related solid-state structure, where enantiomeric pairs of chains combine to give a 1D ribbon motif. The lithium bis(phenylsulfonyl)imides [(PhSO2)2NLi.THF]9 and [(PhSO2)2NLi.Pyr2]10 were also prepared and structurally characterized. In the solid state 9 has a similar connectivity to that found for 1 but with heterochiral chains. In comparison, the more highly solvated complex 10 forms a 1D polymeric arrangement without chelation of the ligands and with the phenyl substituents oriented in a transoid fashion.

Bis(triazacyclohexane) sandwich complexes of (CuI)2, CuII and ZnII: complexes with cuprophilic attraction between two cationic copper(i) leading to unusual reactivity with dioxygen

As the first 1st-row transition metal complexes having six tertiary amine donor groups, bis(triazacyclohexane) sandwich complexes [L2M](BF4)2 (L = benzyl- or p-fluorobenzyl-triazacyclohexane, M = Cu or Zn) have been obtained by the protonolysis of Et2Zn in the presence of L or by reaction of [Cu(MeCN)4](BF4) with L in CH2Cl2 and subsequent air oxidation via an unprecedented Cu(I)(2) sandwich complex containing a short Cu-Cu contact.