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In the title compound, C₁₀H₈N₂·2C₆H₅NO₃, 4-nitrophenol and 4,4′-bipyridine crystallized together in a 2:1 ratio in the space groupP2₁/n. There is a hydrogen-bonding interaction between the nitrogen atoms on the 4,4′-bipyridine molecule and the hydrogen atom on the hydroxyl group on the 4-nitrophenol, resulting in trimolecular units. This structure is a polymorph of a previously reported structure [Nayak & Pedireddi (2016).Cryst. Growth Des.16, 5966–5975], which differs mainly due to a twist in the 4,4′-bipyridine molecule. 

The crystal structure of the title compound, hexaaquanickel(II) dichloride–1,4,7,10,13,16-hexaoxacyclooctadecane–water (1/2/2), [Ni(H₂O)₆]Cl₂·2C₁₂H₂₄O₆·2H₂O, is reported. The asymmetric unit contains half of the Ni(OH₂)₆moiety with a formula of C₁₂H₃₂ClNi_0.50O₁₀at 105 K and triclinic (P1) symmetry. The [Ni(OH₂)₆]²⁺cation has close to ideal octahedral geometry with O—Ni—O bond angles that are within 3° of idealized values. The supramolecular structure includes hydrogen bonding between the water ligands, 18-crown-6 molecules, Cl⁻anions, and co-crystallized water solvent. Two crown ether molecules flank the [Ni(OH₂)₆]²⁺molecule at the axial positions in a sandwich-like structure. The relatively symmetric hydrogen-bonding network is enabled by small Cl⁻counter-ions and likely influences the more idealized octahedral geometry of [Ni(OH₂)₆]²⁺. 

The crystal structure of the title compound, C₁₅H₂₀N₂or^DippIm, is reported. At 106 (2) K, the molecule has monoclinicP2₁/c symmetry with four molecules in the unit cell. The imidazole ring is rotated 80.7 (1)° relative to the phenyl ring. Intermolecular stabilization primarily results from close contacts between the N atom at the 3-position on the imidazole ring and the C—H bond at the 4-position on the neighboring^DippIm, with aryl–aryl distances outside of the accepted distance of 5 Å for π-stacking. 

Abstract Nitrous acid (HONO) plays pivotal roles in various metal‐free as well as metal‐mediated routes relevant to biogeochemistry, atmospheric chemistry, and mammalian physiology. While the metastable nature of HONO hinders the detailed investigations into its reactivity at a transition metal site, this report herein utilizes a heteroditopic copper(II) cryptate [oC]Cu^IIfeaturing a proton‐responsive second‐coordination‐sphere located at a suitable distance from a [Cu^II](ONO) core, thereby enabling isolation of a [Cu^II](κ¹‐ONO⋅⋅⋅H⁺) complex (2H‐NO₂). A set of complementary analytical studies (UV‐vis,¹⁴N/¹⁵N FTIR,¹⁵N NMR, HRMS, EPR, and CHN) on2H‐NO₂and its¹⁵N‐isotopomer (2H‐¹⁵NO₂) reveals the formulation of2H‐NO₂as {[oCH]Cu^II(κ¹‐ONO)}(ClO₄)₂. Non‐covalent interaction index (NCI) based on reduced density gradient (RDG) analysis on {[oCH]Cu^II(κ¹‐ONO)}²⁺discloses a H‐bonding interaction between the apical 3° ammonium site and the nitrite anion bound to the copper(II) site. The FTIR spectra of [Cu^II](κ¹‐ONO⋅⋅⋅H⁺) species (2H‐NO₂) shows a shift of ammonium NH vibrational feature to a lower wavenumber due to the H‐bonding interaction with nitrite. The reactivity profile of [Cu^II](κ¹‐ONO⋅⋅⋅H⁺) species (2H‐NO₂) towards anaerobic nitration of substituted phenol (2,4‐DTBP) is distinctly different relative to that of the closely related tripodal [Cu^II]‐nitrite complexes (1‐NO₂/3‐NO₂/4‐NO₂). 

The title compound, bis(1,2-diphenyl-2-sulfanylideneethanethiolato-κ 2 S , S ′)(1,3,5-triaza-7-phosphaadamantane-κ P )cobalt(II) dichloromethane hemisolvate, [Co(pdt) 2 (PTA)]·0.5C 2 H 4 Cl 2 or [Co(C 14 H 10 S 2 ) 2 (C 6 H 12 N 3 P)]·0.5C 2 H 4 Cl 2 , contains two phenyldithiolene (pdt) ligands and a 1,3,5-triaza-7-phosphaadamantane (PTA) ligand bound to cobalt with the solvent 1,2-dichloroethane molecule located on an inversion center. The cobalt core exhibits an approximately square-pyramidal geometry with partially reduced thienyl radical monoanionic ligands. The supramolecular network is consolidated by hydrogen-bonding interactions primarily with nitrogen, sulfur and chlorine atoms, as well as parallel displaced π-stacking of the aryl rings. The UV–vis, IR, and CV data are also consistent with monoanionic dithiolene ligands and an overall Co II oxidation state. 

Aμ-oxo vanadium(V) dimeric complex, μ-oxido-bis[(2,2′-{[ethane-1,2-diylbis(azanediyl)]bis(methylene)}diphenolato)oxidovanadium(V)], [V₂(C₁₆H₁₈N₂O₂)₂O₃] (1), was crystallized by slow evaporation from an ethanol solution. Theμ-oxo dimer crystallizes in the monoclinic space groupC2/cwhere the salan ligand1acoordinates to the vanadium center in a κ²N,κ²Ofashion, forming a distorted octahedral geometry. The bridging oxo ligand lies on a crystallographic twofold axis. The unit cell consists of four molecules of1that are linked by C—H...·π_areneinteractions as well as intramolecular hydrogen bonding. 

Although copper‐catalyzed organic transformations are prevalent, insights into the interactions of phenols with simple copper(II) salts are not well understood. In contrast, inspired by the oxygenase‐type modifications of the phenolic substrates, the reactions of substituted phenols with metastable copper–oxygen intermediates are well documented. The present report sheds light on the reactions of substituted phenols with benchtop stable CuCl₂salt and the role of a common base like triethylamine. Moreover, the reactions of substituted phenols with CuCl₂in the presence of weakly coordinating tripodalN‐nitrosated ligandL^3NOhave been illustrated, while a closely related tripodal copper(II) complexL^3HCuCl₂(2) of the corresponding non‐nitrosated ligandL^3Hdoes not react with the phenolic substrates. Phenol reactions with CuCl₂in the presence of theL^3NOligand enable in depth mechanistic investigation, thereby illustrating a bimolecular rate law with ΔH^‡= 15.13 kcal mol⁻¹, ΔS^‡ = −9.6 eu, and kinetic isotope effectk₂(ArOH)/k₂(ArOD) in the range of 1.35–1.43. Thus, these findings suggest that simple copper(II) salts like CuCl₂are capable of facilitating a proton‐coupled electron transfer (PCET) pathway. 

Fluorine is an essential component in many highly effective pharmaceutical drugs, however the selective fluorination of organic molecules poses a challenge. A common route to installing fluorine involves C-F bond cleavage, which is often accomplished using second- or third-row transition metals. Base metal catalysts such as nickel may provide a facile, sustainable, and cheaper alternative for C-F activation. Monodentate N-heterocyclic carbene (NHC) nickel complexes have been reported to undergo C-F activation, however bis-bidentate NHC (RNHC2R1; R, R1 = alkyl or aryl) analogs remain underexplored. This work reports a series of RNHC2R1 nickel(0) complexes with various R1 linkers to determine the effect of the linker on the C-F activation of hexafluorobenzene. Comparisons include a reference nickel(0) complex with two monodentate NHC ligands, and results show that low-valent nickel NHC complexes readily break the C-F bond in C6F6 via oxidative addition. Crystallographic and NMR characterization demonstrate that ligand design and denticity affect the cis versus trans orientation of the final product, with the possibility for additional ligand C-H activation.