Stanislav I. Bezzubov

Crystal structure of an unknown solvate of dodecakis­(μ2-alaninato-1:2κ2O:N,O)cerium(III)hexa­nickel(II) aqua­tris­(hydroxido-κO)tris­(nitrato-κ2O,O′)cerate(III)

The chiral title compound, [CeNi6(C3H6NO2)12][Ce(NO3)3(OH)3(H2O)], comprises a complex heterometallic Ni/Ce cation and a homonuclear Ce anion. Both the cation and anion exhibit point group symmetry 3. with the CeIII atom situated on the threefold rotation axis. The cation metal core consists of six NiII atoms coordinated in a slightly distorted octahedral N2O4 configuration by N and O atoms of 12 deprotonated l-alaninate ligands exhibiting both bridging and chelating modes. This metal–organic coordination motif encapsulates one CeIII atom that shows an icosahedral coordination by the O-donor atoms of the l-alaninate ligands, with Ce—O distances varying in the range 2.455 (5)–2.675 (3) Å. In the anion, the central CeIII ion is bound to three bidentate nitrate ligands, to three hydroxide ligands and to one water molecule, with Ce—O distances in the range 2.6808 (19)–2.741 (2) Å. The H atoms of the coordinating water molecule are disordered over three positions due to its location on a threefold rotation axis. Disorder is also observed in fragments of two l-alaninate ligands, with occupancy ratios of 0.608 (14):0.392 (14) and 0.669 (8):0.331 (8), respectively, for the two sets of sites. In the crystal, the complex cations and anions assemble through O—H⋯O and N—H⋯O hydrogen bonds into a three-dimensional network with large voids of approximately 1020 Å3. The contributions of highly disordered ethanol and water solvent molecules to the diffraction data were removed with the SQUEEZE procedure [Spek (2015 ▸). Acta Cryst. C71, 9–18]. The given chemical formula and other crystal data do not take into account the unknown amount of these solvent molecules.

Regioselective Hydrogenolysis of Donor–Acceptor Cyclopropanes with Zn-AcOH Reductive System

A convenient low-cost method for regioselective ring-opening of donor-acceptor cyclopropanes with the Zn-AcOH reductive system was developed. The general character of the method was displayed via efficient reduction of a representative series of 2-(het)arylcyclopropane-1,1-diesters as well as donor-acceptor cyclopropanes with other types of electron-withdrawing activating groups. This method opens a rapid access to γ-substituted propyl-1,1-diesters, ketoesters, cyanoesters, cyanoamides, dinitriles, etc., many of which are not readily accessible with alternative methods. The utility of the synthesized compounds was demonstrated by transforming them into valuable acyclic and cyclic compounds (including pharmacologically relevant carbazoles, δ-lactams, and oxindole derivatives).

Peculiarities of styryl dyes of the benzoselenazole series crystal packings and their influence on solid phase [2 + 2] photocycloaddition reaction with single crystal retention

New styryl dyes of the 2-benzoselenazole series which contain iodide, triiodide, and tosylate anions were synthesized. Crystals of these compounds were grown in different crystal forms – solvent free and hydroquinone, benzene or ethyl acetate solvated ones. X-ray structural studies of the crystals shows that those containing tosylate and triiodide anions form the centrosymmetrically related stacking motif, typical for styryl dye cations and favorable for [2 + 2] photocycloaddition (PCA) reactions. This reaction takes place in crystals with tosylate anions as a single crystal-to-single crystal process. On the contrary, in the triiodide dye crystals, the PCA reaction is lacking, probably due to a weak directional interaction of the selenium atoms with the anions. The iodide dye crystals demonstrate non-typical packing for styryl dyes and manifest as a two-dimensional close packing motif of the cations which is unfavorable for cycloaddition.

Domino construction of a bullataketal core via double bond cleavage in activated dihydrofurans

A novel approach to the tricyclic core of bullataketals A and B, natural benzannulated 2,7-dioxabicyclo[3.2.1]octanes, was developed via a domino reaction including a formal decarbonylation of 3-acyl-4-(o-hydroxyaryl)-substituted 4,5-dihydrofurans followed by spontaneous assembly of the methanobenzodioxepine skeleton. This operationally simple method provides ample opportunities for variation of substituents in the fused benzene moiety as well as at the bridgehead ketal C9 atom of the final products. The successful conversion of both 3-keto- and 3-ester-substituted dihydrofurans into functionalized methanobenzodioxepines pointed toward a substrate-controlled mechanism. This was supported experimentally and by computational studies. While 3-ester-4,5-dihydrofurans are transformed via ring opening/ring closure with further decarboxylation of the generated γ-lactone, 3-keto-4,5-dihydrofurans undergo stepwise CC bond cleavage including intramolecular hemiketalization and retro-aldol reaction as the key steps.

Overcoming the Inertness of Iridium(III) in a Facile Single-Crystal to Single-Crystal Reaction of Iodine Vapor with a Cyclometalated Chloride Monomer

Iridium(III) is often considered to be one of the most inert octahedral metal ions. Herein we present a phenanthroimidazole-based bis-cyclometalated iridium(III) chloride undergoing a facile chloro ligand exchange with iodine, in a gas-solid reaction under ambient conditions. Monitoring the progress of the reaction by X-ray diffraction analysis reveals the crystal-packing-induced exceptional stereoselectivity of this topochemical transformation. The results provide excellent opportunities to modulate the geometry and kinetic properties of cyclometalated iridium(III) complexes that may be very promising in catalysis and design of anticancer agents.

Synthesis and crystal structure of methyl 3-(3-hy­droxy-3-phenyl­prop-2-eno­yl)benzoate

A non-symmetric aromatic β-diketone enol bearing a carboxymethyl group has been synthesized and characterized by X-ray crystallography, 1H and 13C NMR spectroscopy, elemental analysis, UV–Vis spectroscopy and cyclic voltammetry.

Crystal structure of 2,3,5,6-tetra­kis­(pyridin-2-yl)pyrazine hydrogen peroxide 4.75-solvate

The structure of title co-crystal consists of a 2,3,5,6-tetrakis(pyridin-2-yl)pyrazine coformer and hydrogen peroxide solvent molecules in a ratio of 1:4.75.