Acta Crystallographica Section C Structural Chemistry最新文献

The activation of C-C bonds by transition-metal complexes is of continuing interest and acetonitrile (MeCN) has attracted attention as a cyanide source with comparatively low toxicity for organic cyanation reactions. A diiron end-on μ-η¹:η¹-CN-bridged complex was obtained from a crystallization experiment of an open-chain iron-NHC complex, namely, μ-cyanido-κ²C:N-bis{[(acetonitrile-κN)[3,3'-bis(pyridin-2-yl)-1,1'-(methylidene)bis(benzimidazol-2-ylidene)]iron(II)} tris(hexafluorophosphate), [Fe₂(CN)(C₂H₃N)₂(C₂₅H₁₈N₆)₂](PF₆)₃. The cyanide appears to originate from the MeCN solvent by C-C bond cleavage or through carbon-hydrogen oxidation.

Luminescent Cu^I complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title Cu₂I₂P₂S₂-type binuclear complex, di-μ-iodido-bis[(thiourea-κS)(triphenylphosphine-κP)copper(I)], [Cu₂I₂(CH₄N₂S)₂(C₁₈H₁₅P)₂], conventionally abbreviated as Cu₂I₂TPP₂TU₂, where TPP and TU represent triphenylphosphine and thiourea, respectively, is described. In this complex, each Cu^I atom adopts a CuI₂PS four-coordination mode and pairs of atoms are connected to each other by two μ₂-I ligands to form a centrosymmetric binuclear cluster. It was also found that the paper-based film of this complex exhibited obvious luminescence light-up sensing for pyridine and 4-methylpyridine.

During the course of exploring crystallization conditions in generating metal-organic frameworks (MOFs) for use in the crystalline sponge method, two discrete metal-organic complexes, namely, aqua[2,4,6-tris(pyridin-4-yl)-1,3,5-triazine]zinc(II) bromide, [Zn(C₁₈H₁₂N₆)(H₂O)]Br₂, and aqua[2,4,6-tris(pyridin-4-yl)-1,3,5-triazine]zinc(II) chloride, [Zn(C₁₈H₁₂N₆)(H₂O)]Cl₂, were encountered. Structures in the orthorhombic space group Pnma (No. 62) for the bromide congener at 299 K and the chloride congener at 100 K were obtained. A phase transition for the bromide congener occurred upon cooling from 299 to 100 K, yielding a crystal polymorph with four domains that exhibits monoclinic P2₁/m space-group symmetry (No. 11), which arises from conformational changes. The main intramolecular contacts that contribute to the crystal packing in all observed structures are H...H, Halide...H/H...Halide, C...H/H...C, and N...H/H...N. Intramolecular hydrogen bonding between the Zn-bound water and non-Zn-bound pyridyl N atoms is a prominent feature within the three-dimensional networks. Aromatic π-stacking between the non-Zn-bound pyridine rings and contacts involving the halide ligands further stabilize the crystal packing.

Three structurally diverse 5-phenyltetrazolato (Tz) Ti, Zr, and Ta complexes, namely, (C₂H₈N)[Ti₂(C₇H₅N₄)₅(C₂H₆N)₄]·1.45C₆H₆ or (Me₂NH₂)[Ti₂(NMe₂)₄(2,3-μ-Tz)₃(2-η¹-Tz)₂]·1.45C₆H₆, (1·1.45C₆H₆), [Zr₂(C₇H₅N₄)₆(C₂H₆N)₂(C₂H₇N)₂]·1.12C₆H₆·0.382CH₂Cl₂ or [Zr₂(Me₂NH)₂(NMe₂)₂(2,3-μ-Tz)₃(2-η¹-Tz)₂(1,2-η²-Tz)]·1.12C₆H₆·0.38CH₂Cl₂ (2·1.12C₆H₆·0.38CH₂Cl₂), and (C₂H₈N)₂[Ta₂(C₇H₅N₄)₈(C₂H₆N)₂O]·0.25C₇H₈ or (Me₂NH₂)₂[Ta₂(NMe₂)₂(2,3-μ-Tz)₂(2-η¹-Tz)₆O]·0.25C₇H₈ (3·0.25C₇H₈), where TzH is 5-phenyl-1H-tetrazole, have been synthesized and structurally characterized. All three complexes are dinuclear; the Ti center in 1 is six-coordinate, whereas the Zr and Ta atoms in 2 and 3 are seven-coordinate. The coordination environments of the Ti centers in 1 are similar, and so are the ligations of the Ta centers in 3. In contrast, the two Zr centers in 2 bear a different number of ligands, one of which is a bidentate η²-5-phenyltetrazolato ligand that has not been observed previously for d-block elements. The dimethylamido ligand, present in the starting materials, remained unchanged, or was converted to dimethylamine and dimethylammonium during the synthesis. Dimethylamine coordinates as a neutral ligand, whereas dimethylammonium is retained as a hydrogen-bonded entity bridging Tz ligands.

The article of Sommer [Acta Cryst. (2024), C80, 337-342] provides a concise and effective introduction to the subject of growing crystals suitable for structure determination.

Dicarbonyl[10,10-dimethyl-5,15-bis(pentafluorophenyl)biladiene]ruthenium(II), [Ru(C₃₃H₁₆F₁₀N₄)(CO)₂] or Ru(CO)₂[DMBil1], is the first reported ruthenium(II) cis-dicarbonyl tetrapyrrole complex. The neutral complex sports two carbonyls and an oligotetrapyrrolic biladiene ligand. Notably, the biladiene adopts a coordination geometry that is well distorted from square planar and much more closely approximates a seesaw arrangement. Accordingly, Ru(CO)₂[DMBil1] is not only the first ruthenium cis-dicarbonyl with a tetrapyrrole ligand, but also the first metal biladiene complex in which the tetrapyrrole does not adopt a (pseudo-)square-planar coordination geometry. Ru(CO)₂[DMBil1] is weakly luminescent, displaying λ_em = 552 nm upon excitation at λ_ex = 500 nm, supports two reversible 1 e^- reductions at -1.45 and -1.73 V (versus Fc⁺/Fc), and has significant absorption features at 481 and 531 nm, suggesting suitability for photocatalytic and photosensitization applications. While the structure of Ru(CO)₂[DMBil1] was initially determined by X-ray diffraction, a traditionally acceptable quality structure could not be obtained (despite multiple attempts) because of consistently poor crystal quality. An independent structure obtained from electron diffraction experiments corroborates the structure of this unusual biladiene complex.

Chalcopyrite, the world's primary copper ore mineral, is abundant in Latin America. Copper extraction offers significant economic and social benefits due to its strategic importance across various industries. However, the hydrometallurgical route, considered more environmentally friendly for processing low-grade chalcopyrite ores, remains challenging, as does its concentration by froth flotation. This limited understanding stems from the poorly understood structure and reactivity of chalcopyrite surfaces. This study reviews recent contributions using density functional theory (DFT) calculations with periodic boundary conditions and slab models to elucidate chalcopyrite surface properties. Our analysis reveals that reconstructed surfaces preferentially expose S atoms at the topmost layer. Furthermore, some studies report the formation of disulfide groups (S₂^2-) on pristine sulfur-terminated surfaces, accompanied by the reduction of Fe³⁺ to Fe²⁺, likely due to surface oxidation. Additionally, Fe sites are consistently identified as favourable adsorption locations for both oxygen (O₂) and water (H₂O) molecules. Finally, the potential of computer modelling for investigating collector-chalcopyrite surface interactions in the context of selective froth flotation is discussed, highlighting the need for further research in this area.

Treating the amide acetanilide (N-phenylacetamide, C₈H₉NO) with aqueous strong acids allowed the structures of five hemi-protonated salt forms of acetanilide to be elucidated. N-(1-Hydroxyethylidene)anilinium chloride-N-phenylacetamide (1/1), [(C₈H₉NO)₂H][Cl], and the bromide, [(C₈H₉NO)₂H][Br], triiodide, [(C₈H₉NO)₂H][I₃], tetrafluoroborate, [(C₈H₉NO)₂H][BF₄], and diiodobromide hemi(diiodine), [(C₈H₉NO)₂H][I₂Br]·0.5I₂, analogues all feature centrosymmetric dimeric units linked by O-H...O hydrogen bonds that extend into one-dimensional hydrogen-bonded chains through N-H...X interactions, where X is the halide atom of the anion. Protonation occurs at the amide O atom and results in systematic lengthening of the C=O bond and a corresponding shortening of the C-N bond. The size of these geometric changes is similar to those found for hemi-protonated paracetamol structures, but less than those in fully protonated paracetamol structures. The bond angles of the amide fragments are also found to change on protonation, but these angular changes are also influenced by conformation, namely, whether the amide group is coplanar with the phenyl ring or twisted out of plane.

A long-standing issue about the correct identification of an important starting reagent, iron(III) hexafluoroacetylacetonate, Fe(hfac)₃ (1), has been resolved. The tris-chelated mononuclear complex was found to crystallize in two polymorph modifications which can be assigned as the low-temperature (1-L) monoclinic P2₁/n and the high-temperature (1-H) trigonal P-3. Low-temperature polymorph 1-L was found to transform to 1-H upon sublimation at 44 °C. Two modifications are clearly distinguished by powder X-ray diffraction (PXRD), single-crystal X-ray diffraction, differential scanning calorimetry (DSC), and melting-point measurements. On the other hand, the two forms share similar characteristics in direct analysis in real-time mass spectrometry (DART-MS), attenuated total reflection (ATR) spectroscopy, and some physical properties, such as color, volatility, sensitivity, and solubility. Analysis of the literature and some of our preliminary data strongly suggest that the appearance of two polymorph modifications for trivalent metal (both transition and main group) hexafluoroacetylacetonates is a common case for several largely used complexes not yet accounted for in the crystallographic databases.

Herein we report the crystal structures of two benzodiazepines obtained by reacting N,N'-(4,5-diamino-1,2-phenylene)bis(4-methylbenzenesulfonamide) (1) or 4,5-(4-methylbenzenesulfonamido)benzene-1,2-diaminium dichloride (1·2HCl) with acetone, giving 2,2,4-trimethyl-8,9-bis(4-methylbenzenesulfonamido)-2,3-dihydro-5H-1,5-benzodiazepine, C₂₆H₃₀N₄O₄S₂ (2), and 2,2,4-trimethyl-8,9-bis(4-methylbenzenesulfonamido)-2,3-dihydro-5H-1,5-benzodiazepin-1-ium chloride 0.3-hydrate, C₂₆H₃₁N₄O₄S₂⁺·Cl^-·0.3H₂O (3). Compounds 2 and 3 were first obtained in attempts to recrystallize 1 and 1·2HCl using acetone as solvent. This solvent reacted with the vicinal diamines present in the molecular structures, forming a 5H-1,5-benzodiazepine ring. In the crystal structure of 2, the seven-membered ring of benzodiazepine adopts a boat-like conformation, while upon protonation, observed in the crystal structure of 3, it adopts an envelope-like conformation. In both crystalline compounds, the tosylamide N atoms are not in resonance with the arene ring, mainly due to hydrogen bonds and steric hindrance caused by the large vicinal groups in the aromatic ring. At a supramolecular level, the crystal structure is maintained by a combination of hydrogen bonds and hydrophobic interactions. In 2, amine-to-tosyl N-H...O and amide-to-imine N-H...N hydrogen bonds can be observed. In contrast, in 3, the chloride counter-ion and water molecule result in most of the hydrogen bonds being of the amide-to-chloride and ammonium-to-chloride N-H...Cl types, while the amine interacts with the tosyl group, as seen in 2. In conclusion, we report the synthesis of 1, 1·2HCl and 2, as well as their chemical characterization. For 2, two synthetic methods are described, i.e. solvent-mediated crystallization and synthesis via a more efficient and cleaner route as a polycrystalline material. Salt 3 was only obtained as presented, with only a few crystals being formed.