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A series of hydrogen-bonding catalysts have been designed for the aromatic Claisen rearrangement of a 1,1-dimethylallyl coumarin. These catalysts were designed as mimics of the two-point hydrogen-bonding interaction present in ketosteroid isomerase that has been proposed to stabilize a developing negative charge on the ether oxygen in the migration of the double bond.1 Two hydrogen bond donating groups, a phenol alcohol and a carboxylic acid, were grafted onto a conformationally restrained spirocyclic scaffold, and together they enhance the rate of the Claisen rearrangement by a factor of 58 over the background reaction. Theoretical calculations correctly predict the most active catalyst and suggest that both preorganization and favorable interactions with the transition state of the reaction are responsible for the observed rate enhancement.

N-Butyl-2,3-bis(dicyclohexylamino)cyclopropenimine (1) crystallizes from benzene and hexanes in the presence of HCl as a monobenzene solvate of the hydrochloride salt, [1H]Cl⋅C6H6 or C31H54N3 +⋅Cl⋅C6H6, in the P21/n space group. The protonation of 1 results in the generation of an aromatic structure based upon the delocalization of the cyclopropene double bond around the cyclopropene ring, giving three intermediate C--C bond lengths of 1.41 A °, and the delocalization of the imine-type C--N double bond, giving three intermediate C--N bond lengths of 1.32 A °. Ion-ion and ion-benzene packing interactions are described and illustrated. [ABSTRACT FROM AUTHOR]

The crystal structures of two closely related compounds, 1-cyclo­hexyl-2-(2-nitro­phen­yl)-1,3-thia­zolidin-4-one, C15H18N2O3S, (1) and 1-cyclo­hexyl-2-(2-nitro­phen­yl)-1,3-thia­zolidin-4-one 1,1-dioxide, C15H18N2O5S, (2), are presented. These compounds are comprised of three types of rings: thia­zolidinone, nitrophenyl and cyclo­hexyl. In both structures, the rings are close to mutually perpendicular, with inter­planar dihedral angles greater than 80° in each case. The thia­zol­idinone rings in both structures exhibit envelope puckering with the S atom as flap and the cyclo­hexyl rings are in their expected chair conformations. The two structures superpose fairly well, except for the orientation of the nitro groups with respect to their host phenyl ring, with a difference of about 10° between 1 and 2. The extended structure of 1 has two kinds of weak C—H. . .O inter­actions, giving rise to a closed ring formation involving three symmetry-related molecules. Structure 2 has four C—H. . .O inter­actions, two of which are exclusively between symmetry-related thia­zolidinone dioxide moieties and have a parallel `give-and-take-fashion' counterpart. In the other two inter­actions, the nitrophenyl ring and the cyclo­hexane ring each offer an H atom to the two O atoms on the sulfone group. Additionally, a C—H. . .π inter­action between a C—H group of the cyclo­hexane ring and the nitrophenyl ring of an adjacent mol­ecule helps to consolidate the structure. [ABSTRACT FROM AUTHOR]

The solid-state structures of the Na+, Li+, and NH4+ salts of the 4,5-dihydroxybenzene-1,3-disulfonate (tiron) dianion are reported, namely disodium 4,5-dihydroxybenzene-1,3-disulfonate, 2Na+·C6H4O8S22-,·-4,5-dihydroxybenzene-1,3-disulfonato-bis[aqualithium(I)] hemihydrate, [Li2(C6H4O8S2)(H2O)2]·0.5H2O, and diammonium 4,5-dihydroxybenzene-1,3-disulfonate monohydrate, 2NH4+·C6H4O8S22-·H2O. Intermolecular interactions vary with the size of the cation, and the asymmetric unit cell, and the macromolecular features are also affected. The sodium in Na2(tiron) is coordinated in a distorted octahedral environment through the sulfonate oxygen and hydroxyl oxygen donors on tiron, as well as an interstitial water molecule. Lithium, with its smaller ionic radius, is coordinated in a distorted tetrahedral environment by sulfonic and phenolic O atoms, as well as water in Li2(tiron). The surrounding tiron anions coordinating to sodium or lithium in Na2(tiron) and Li2(tiron), respectively, result in a three-dimensional network held together by the coordinate bonds to the alkali metal cations. The formation of such a three-dimensional network for tiron salts is relatively rare and has not been observed with monovalent cations. Finally, (NH4)2(tiron) exhibits extensive hydrogen-bonding arrays between NH4+ and the surrounding tiron anions and interstitial water molecules. This series of structures may be valuable for understanding charge transfer in a putative solid-state fuel cell utilizing tiron. [ABSTRACT FROM AUTHOR]

Birnessite, a layered-structure MnO2, is an earth-abundant functional material with potential for various energy and environmental applications, such as water oxidation. An important feature of birnessite is the existence of Mn(III) within the MnO2 layers, accompanied by interlayer charge-neutralizing cations. Using first-principles calculations, we reveal the nature of Mn(III) in birnessite with the concept of the small polaron, a special kind of point defect. Further taking into account the effect of the spatial distribution of Mn(III), we propose a theoretical model to explain the structure-performance dependence of birnessite as an oxygen evolution catalyst. We find an internal potential step which leads to the easy switching of the oxidation state between Mn(III) and Mn(IV) that is critical for enhancing the catalytic activity of birnessite. Finally, we conduct a series of comparative experiments which support our model. [ABSTRACT FROM AUTHOR]

Polynuclear metal clusters frequently feature geometric structural features not common in traditional coordination chemistry. These structures are of particular interest to bioinorganic chemists studying metallocluster enzymes, which frequently possess remarkably unusual inorganic structures. The structure of the manganese cluster μ5-oxido-di-μ3-phenoxido-hexa-μ-phenoxido-hexakis(pyridine-κ N)hexamanganese(II) pyridine monosolvate, [Mn5(C6H5O)8O(C5H5N)6]·C5H5N or MnII5(μ-OPh)6(μ3-OPh)2(μ5-O)(Py)6·Py, containing an unusual trigonal bipyramidal central oxide, is described. The compound was isolated from a reaction mixture containing bis(trimethylsilylamido)manganese(II) and phenol. The central O atom is presumed to have originated as adventitious water. The molecule crystalizes in a primitive monoclinic crystal system and is presented in the centrosymetric P2/ n space group. The molecule possesses crystallographically imposed twofold symmetry, with the central O atom centred on the twofold axis and surrounded by a distorted trigonal bipyramidal arrangement of Mn atoms, which are further bridged by phenoxide ligands, and terminally ligated by pyridine. A pyridine solvent molecule resides nearby, also situated on a crystallographic twofold axis. The cluster is compared to three closely related previously reported structures. [ABSTRACT FROM AUTHOR]

Due to the flammability of liquid electrolytes used in lithium ion batteries, solid lithium ion conductors are of interest to reduce danger and increase safety. The two dominating general classes of electrolytes under exploration as alternatives are ceramic and polymer electrolytes. Our group has been exploring the preparation of molecular solvates of lithium salts as alternatives. Dissolution of LiCl or LiPF6 in pyridine (py) or vinylpyridine (VnPy) and slow vapor diffusion with diethyl ether gives solvates of the lithium salts coordinated by pyridine ligands. For LiPF6, the solvates formed in pyridine and vinylpyridine, namely tetrakis(pyridine-κ N)lithium(I) hexafluorophosphate, [Li(C5H5N)4]PF6, and tetrakis(4-ethenylpyridine-κ N)lithium(I) hexafluorophosphate, [Li(C7H7N)4]PF6, exhibit analogous structures involving tetracoordinated lithium ions with neighboring PF6− anions in the I and Aea2 space groups, respectively. For LiCl solvates, two very different structures form. catena-Poly[[(pyridine-κ N)lithium]-μ3-chlorido], [LiCl(C5H5N)] n, crystalizes in the P212121 space group and contains channels of edge-fused LiCl rhombs templated by rows of π-stacked pyridine ligands, while the structure of the LiCl-VnPy solvate, namely di-μ-chlorido-bis[bis(4-ethenylpyridine-κ N)lithium], [Li2Cl2(C7H7N)4], is described in the P21/ n space group as dinuclear (VnPy)2Li(μ-Cl)2Li(VnPy)2 units packed with neighbors via a dense array of π-π interactions. [ABSTRACT FROM AUTHOR]

Solvent-free single crystals of 1,3,5,7,9,11,13,15-octaphenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (abbreviated as octaphenyl-POSS), C48H40O12Si8, were obtained by dehydration/condensation of the tetrol Si4O4(Ph)4(OH)4. The powder pattern generated from the single-crystal data matches well with the experimentally measured powder pattern of commercial octaphenyl-POSS. The geometry of the centrosymmetric molecule in the crystal was compared with that in the gas phase, and had shorter Si-O bond lengths and a broader range of Si-O-Si bond angles. The average Si-O bond length [1.621 (3) Å], and Si-O-Si and O-Si-O bond angles [149 (5) and 109 (1)°, respectively] were within the same range measured previously for octaphenyl-POSS solvates. [ABSTRACT FROM AUTHOR]

The article focuses on the trans-Bis(hinokitiolato)copper(II) trans-bis(hinokitiolato)palladium(II) cocyrstals with (5/1) and (3/2) formulations which contain molecules possessing crystallographic inversion symmetry. Hinokitiol has antitumor, antibacterial and antifungal properties. Metal complexes of the hinokitolate anion show antiviral and antimicrobial properties. The bis(hinokitiolato)copper(II) exists in at least three crystalline modifications including polymorphic that has four crystalline forms.

N -Butyl-2,3-bis-(di-cyclo-hexyl-amino)-cyclo-propenimine ( 1 ) crystallizes from benzene and hexa-nes in the presence of HCl as a mono-benzene solvate of the hydro-chloride salt, [ 1 H]Cl·C 6 H 6 or C 31 H 54 N 3 + ·Cl - ·C 6 H 6 , in the P 2 1 / n space group. The protonation of 1 results in the generation of an aromatic structure based upon the delocalization of the cyclo-propene double bond around the cyclo-propene ring, giving three inter-mediate C-C bond lengths of ∼1.41 Å, and the delocalization of the imine-type C-N double bond, giving three inter-mediate C-N bond lengths of ∼1.32 Å. Ion-ion and ion-benzene packing inter-actions are described and illustrated., (© Muñoz Sánchez and Zdilla 2022.)

A new type of crystalline solid, termed "solvate sponge crystal", is presented, and the chemical basis of its properties are explained for a melt- and press-castable solid sodium ion conductor. X-ray crystallography and atomistic simulations reveal details of atomic interactions and clustering in (DMF) 3 NaClO 4 and (DMF) 2 NaClO 4 (DMF = N-N '-dimethylformamide). External pressure or heating results in reversible expulsion of liquid DMF from (DMF) 3 NaClO 4 to generate (DMF) 2 NaClO 4 . The process reverses upon the release of pressure or cooling. Simulations reveal the mechanism of crystal "juicing," as well as melting. In particular, cation-solvent clusters form a chain of octahedrally coordinated Na + -DMF networks, which have perchlorate ions present in a separate sublattice space in 3 : 1 stoichiometry. Upon heating and/or pressing, the Na + ⋯DMF chains break and the replacement of a DMF molecule with a ClO 4 - anion per Na + ion leads to the conversion of the 3 : 1 stoichiometry to a 2 : 1 stoichiometry. The simulations reveal the anisotropic nature of pressure induced stoichiometric conversion. The results provide molecular level understanding of a solvate sponge crystal with novel and desirable physical castability properties for device fabrication., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Cyanuric triazide reacts with several transition metal precursors, extruding one equivalent of N 2 and reducing the putative diazidotriazeneylnitrene species by two electrons, which rearranges to N -(1' H -[1,5'-bitetrazol]-5-yl)methanediiminate (biTzI 2- ) dianionic ligand, which ligates the metal and dimerizes, and is isolated from pyridine as [M(biTzI)] 2 Py 6 (M = Mn, Fe, Zn, Cu, Ni). Reagent scope, product analysis, and quantum chemical calculations were combined to elucidate the mechanism of formation as a two-electron reduction preceding ligand rearrangement., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The solid-state structures of the Na + , Li + , and NH 4 + salts of the 4,5-di-hydroxy-benzene-1,3-di-sulfonate (tiron) dianion are reported, namely disodium 4,5-di-hydroxy-benzene-1,3-di-sulfonate, 2Na + ·C 6 H 4 O 8 S 2 2- , μ-4,5-di-hydroxy-benzene-1,3-di-sulfonato-bis-[aqua-lithium(I)] hemihydrate, [Li 2 (C 6 H 4 O 8 S 2 )(H 2 O) 2 ]·0.5H 2 O, and di-ammonium 4,5-di-hydroxy-benzene-1,3-di-sulfonate monohydrate, 2NH 4 + ·C 6 H 4 O 8 S 2 2- ·H 2 O. Inter-molecular inter-actions vary with the size of the cation, and the asymmetric unit cell, and the macromolecular features are also affected. The sodium in Na 2 (tiron) is coordinated in a distorted octa-hedral environment through the sulfonate oxygen and hydroxyl oxygen donors on tiron, as well as an inter-stitial water mol-ecule. Lithium, with its smaller ionic radius, is coordinated in a distorted tetra-hedral environment by sulfonic and phenolic O atoms, as well as water in Li 2 (tiron). The surrounding tiron anions coordinating to sodium or lithium in Na 2 (tiron) and Li 2 (tiron), respectively, result in a three-dimensional network held together by the coordinate bonds to the alkali metal cations. The formation of such a three-dimensional network for tiron salts is relatively rare and has not been observed with monovalent cations. Finally, (NH 4 ) 2 (tiron) exhibits extensive hydrogen-bonding arrays between NH 4 + and the surrounding tiron anions and inter-stitial water mol-ecules. This series of structures may be valuable for understanding charge transfer in a putative solid-state fuel cell utilizing tiron.

Due to the flammability of liquid electrolytes used in lithium ion batteries, solid lithium ion conductors are of interest to reduce danger and increase safety. The two dominating general classes of electrolytes under exploration as alternatives are ceramic and polymer electrolytes. Our group has been exploring the preparation of molecular solvates of lithium salts as alternatives. Dissolution of LiCl or LiPF 6 in pyridine (py) or vinylpyridine (VnPy) and slow vapor diffusion with diethyl ether gives solvates of the lithium salts coordinated by pyridine ligands. For LiPF 6 , the solvates formed in pyridine and vinylpyridine, namely tetrakis(pyridine-κN)lithium(I) hexafluorophosphate, [Li(C 5 H 5 N) 4 ]PF 6 , and tetrakis(4-ethenylpyridine-κN)lithium(I) hexafluorophosphate, [Li(C 7 H 7 N) 4 ]PF 6 , exhibit analogous structures involving tetracoordinated lithium ions with neighboring PF 6 - anions in the I-4 and Aea2 space groups, respectively. For LiCl solvates, two very different structures form. catena-Poly[[(pyridine-κN)lithium]-μ 3 -chlorido], [LiCl(C 5 H 5 N)] n , crystalizes in the P2 1 2 1 2 1 space group and contains channels of edge-fused LiCl rhombs templated by rows of π-stacked pyridine ligands, while the structure of the LiCl-VnPy solvate, namely di-μ-chlorido-bis[bis(4-ethenylpyridine-κN)lithium], [Li 2 Cl 2 (C 7 H 7 N) 4 ], is described in the P2 1 /n space group as dinuclear (VnPy) 2 Li(μ-Cl) 2 Li(VnPy) 2 units packed with neighbors via a dense array of π-π interactions.

Polynuclear metal clusters frequently feature geometric structural features not common in traditional coordination chemistry. These structures are of particular interest to bioinorganic chemists studying metallocluster enzymes, which frequently possess remarkably unusual inorganic structures. The structure of the manganese cluster μ 5 -oxido-di-μ 3 -phenoxido-hexa-μ-phenoxido-hexakis(pyridine-κN)hexamanganese(II) pyridine monosolvate, [Mn 5 (C 6 H 5 O) 8 O(C 5 H 5 N) 6 ]·C 5 H 5 N or Mn II 5 (μ-OPh) 6 (μ 3 -OPh) 2 (μ 5 -O)(Py) 6 ·Py, containing an unusual trigonal bipyramidal central oxide, is described. The compound was isolated from a reaction mixture containing bis(trimethylsilylamido)manganese(II) and phenol. The central O atom is presumed to have originated as adventitious water. The molecule crystalizes in a primitive monoclinic crystal system and is presented in the centrosymetric P2/n space group. The molecule possesses crystallographically imposed twofold symmetry, with the central O atom centred on the twofold axis and surrounded by a distorted trigonal bipyramidal arrangement of Mn atoms, which are further bridged by phenoxide ligands, and terminally ligated by pyridine. A pyridine solvent molecule resides nearby, also situated on a crystallographic twofold axis. The cluster is compared to three closely related previously reported structures.