A second solvatomorph of poly[[μ4-N,N′-(1,3,5-oxadiazinane-3,5-diyl)bis(carbamoylmethanoato)]nickel(II)dipotassium]: crystal structure, Hirshfeld surface analysis and semi-empirical geometry optimization

The title compound, poly[triaquabis[μ4-N,N′-(1,3,5-oxadiazinane-3,5-diyl)bis(carbamoylmethanoato)]dinickel(II)tetrapotassium], [K4Ni2(C7H6N4O7)2(H2O)3] n , is a second solvatomorph of poly[(μ4-N,N′-(1,3,5-oxadiazinane-3,5-diyl)bis(carbamoylmethanoato)nickel(II)dipotassium] reported previously [Plutenko et al. (2021). Acta Cryst. E77, 298–304]. The asymmetric unit of the title compound includes two structurally independent complex anions [Ni(C7H6N4O7)]2−, which exhibit an L-shaped geometry and consist of two almost flat fragments perpendicular to one another: the 1,3,5-oxadiazinane fragment and the fragment including other atoms of the anion. The central Ni atom is in a square-planar N2O2 coordination arrangement formed by two amide N and two carboxylate O atoms. In the crystal, the title compound forms a layered structure in which layers of negatively charged complex anions and positively charged potassium cations are stacked along the a-axis direction. The polymeric framework is stabilized by a system of hydrogen-bonding interactions in which the water molecules act as donors and the carboxylic, amide and water O atoms act as acceptors.

First-Principles Study on the Mechanism of Greenhouse Gas Generation in Aluminum Electrolysis

Greenhouse gases emitted by the aluminum electrolysis industry have brought great challenges to environmental protection. To address this problem, understanding the micro-generation mechanism of greenhouse gases in the electrolysis process is of great significance to their source suppression. Based on the first principles calculation method, the formation paths of CO, CO2 and COF2 during normal electrolysis were obtained by studying the adsorption behavior of oxygen and fluorine complex anions (short for [O]2−, [F]−) on the anode surface in cryolite alumina molten salt. The calculation results indicate that the O and F atoms prefer to adsorb at bridge site 1 of Model A, with the adsorption energies of −4.82 eV and −3.33 eV. In the [O]2− priority discharge stage, Path 3 is the most likely path for CO2 generation, while in the [O]2−, [F]− co-discharge stage, Path 3 is the most likely path for COF2 generation. It is deduced that the thermal decomposition of COF2 at high temperature should account for the generation of CF4 with a low concentration of the so-called non-anode effect PFC (NAE-PFC). Experiments were also conducted to verify the calculation by disclosing the bonding information of C, O and F, which are in good accordance with the results calculated by the first principle.

A Structure Hierarchy for the Aluminofluoride Minerals

ABSTRACT The structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerization of coordination polyhedra of higher bond-valence, and such hierarchies are useful in understanding the general compositional, structural, and paragenetic variations within the structural group of interest. Here we develop a structure hierarchy for the aluminofluoride minerals based on the polymerization of the dominant (AlΦ6) octahedra and their linkage with other strongly bonded complex anionic groups. The minerals are divided first into the following categories: (1) simple aluminofluorides and (2) compound aluminofluorides containing other oxyanions. The minerals are then ordered according to the polymerization of the constituent polyhedra into a coherent structural hierarchy. The chemical composition and crystal-chemical details of the ions of the interstitial complex are a collective function of the Lewis acidity of the interstitial cations; the presence of interstitial anions, both simple [F–, (OH)–] and complex [(SO4)2–]; self-polymerization of the (AlF6)3– octahedra; and polymerization with both Mg(F,OH)6 octahedra and other complex anions: (SO4)2–, (PO4)3–, (CO3)2–.

Stabilization of Superionic-Conducting High-Temperature Phase of Li(Cb9h10) via Solid Solution Formation with Li2(B12H12)

We report the stabilization of the high-temperature (high-T) phase of lithium carba-closo-decaborate, Li(CB9H10), via the formation of solid solutions in a Li(CB9H10)-Li2(B12H12) quasi-binary system. Li(CB9H10)-based solid solutions in which [CB9H10]− is replaced by [B12H12]2− were obtained at compositions with low x values in the (1−x)Li(CB9H10)−xLi2(B12H12) system. An increase in the extent of [B12H12]2− substitution promoted stabilization of the high-T phase of Li(CB9H10), resulting in an increase in the lithium-ion conductivity. Superionic conductivities of over 10−3 S cm−1 were achieved for the compounds with 0.2 ≤ x ≤ 0.4. In addition, a comparison of the Li(CB9H10)−Li2(B12H12) system and the Li(CB9H10)−Li(CB11H12) system suggests that the valence of the complex anions plays an important role in the ionic conduction. In battery tests, an all-solid-state Li–TiS2 cell employing 0.6Li(CB9H10)−0.4Li2(B12H12) (x = 0.4) as a solid electrolyte presented reversible battery reactions during repeated discharge–charge cycles. The current study offers an insight into strategies to develop complex hydride solid electrolytes.

Crystal structure and Hirshfeld surface analysis of poly[[bis[μ4-N,N′-(1,3,5-oxadiazinane-3,5-diyl)bis(carbamoylmethanoato)]nickel(II)tetrapotassium] 4.8-hydrate]

The title compound, {[K4Ni2(C7H6N4O7)2]·4.8H2O} n , was obtained as a result of a template reaction between oxalohydrazidehydroxamic acid, formaldehyde and nickel(II) nitrate followed by partial hydrolysis of the formed intermediate. The two independent [Ni(C7H6N4O7)]2– complex anions exhibit pseudo-C S symmetry and consist of an almost planar metal-containing fragment and a 1,3,5-oxadiazinane ring with a chair conformation disposed nearly perpendicularly with respect to the former. The central NiII atom has a square-planar N2O2 coordination arrangement formed by two amide N and two carboxylate O atoms. In the crystal, the nickel(II) complex anions form layers parallel to the ab plane. Neighboring complex anion layers are connected by layers of potassium cations for which two of the four independent cations are disordered over two sites [ratios of 0.54 (3):0.46 (3) and 0.9643 (15):0.0357 (15)]. The framework is stabilized by an extensive system of hydrogen bonds where the water molecules act as donors and the carboxylic O atoms, the amide O atoms and the oxadiazinane N atoms act as acceptors.