Structural and physicochemical characteristics of chelate nickel(II) compounds based on 1,2,3-triketone (hydrazone)imines

The crystal structures of the chelates Ni^IIL (L²⁻ are the N,N′-(o-phenylene)-bis[4-(4-methylphenyl)hydrazono-3-oxo-1,1,2,2-tetrafluorononane-5-iminate], N,N′-ethylene-bis[3-(4-methylphenyl)hydrazono-4-oxo-5,5,6,6,7,7,8,8-octafluorooctane-2-iminate], or N,N′-ethylene-bis(4-hydroxy-5,5,6,6,7,7,8,8-octafluoro-3-octene-2-iminate) anions) were studied by X-ray diffraction. Magnetic measurements and ESR spectroscopic studies revealed the appearance of paramagnetism due to a tetrahedral distortion of the coordination unit and also the unusual behavior of the effective magnetic moment at low temperatures. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 103–109, January, 2007.     

Condensation of fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones with methylamine

Fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones react with methylamine in different ways, depending on the substrate structure. Arylhydrazones having a short fluoroalkyl substituent (R_F = CF₃, HCF₂CF₂) react at the carbonyl group adjacent to the nonfluorinated substituent to give 3-alkyl(aryl)-2-aryldiazenyl-3-methylamino-1-polyfluoroalkylprop-2-en-1-ones. Arylhydrazones with a long-chain fluoroalkyl group (R_F = C₃F₇ and longer) and a bulky nonfluorinated group take up methylamine molecule at the carbonyl group linked to the fluorinated substituent, and the subsequent haloform reaction yields N-methyl-2-arylhydrazono-3-oxobutanamides. Both types of products are formed in reactions of methylamine with 1,2,3-triketone 2-arylhydrazones having a long fluoroalkyl group and methyl group at the other carbonyl group. Template condensation of fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones with methylamine over Ni(II) template gives bis[3-alkyl(aryl)-1-polyfluoroalkyl-3-methylamino-2-aryldiazenylprop-2-en-1-onato-N,N′]-nickel(II), regardless of the size of the fluoroalkyl substituent. The same complexes and their copper analogs can be obtained by treatment of 3-alkyl(aryl)-2-aryldiazenyl-3-methylamino-1-polyfluoroalkylprop-2-en-1-ones with the corresponding metal salts.     

Crystal and Molecular Structures of N-Ethylquinolinium Triiodide

Complexation in the N-ethylquinolinium iodide–molecular iodine system in a chloroform solution is studied. The stability constant of N-ethylquinolinium triiodide (I) is determined by spectrophotometric methods of stoichiometric dilution using the average iodine number function. Compound I with the [C₉H₇NC₂H₅]I₃ composition is studied by X-ray diffraction analysis. The crystal structure is formed by alternating layers of cations arranged by the ladder type and triiodide anions with equalized interatomic distances. The triiodide anions are linked to form chains through strongly shortened intermolecular contacts.     

Organometallic synthesis, molecular structure, and coloration of 2,7-disubstituted 1,8-bis(dimethylamino)naphthalenes. How significant is the influence of "buttressing effect" on their basicity?

On treatment of 2,7-dilithio- (6a) and 2,7-bis(bromomagnesio)- (6b) naphthalenes with a number of electrophiles, new "proton sponge" derivatives 7a-e,g, containing iodo, methylthio, trimethylsilyl, methyl, n-butyl, and ethoxycarbonyl groups in ortho-positions to dimethylamino groups, have been synthesized. The investigation of their molecular structure, spectral characteristics, and basicity reveals that the latter is mainly determined by two groups of factors: (1) the polar effect of ortho-substituents and (2) the so-called "buttressing effect" representing the complex combination of various sterical interactions of ortho-substituents with dimethylamino groups in corresponding bases and cations. A contradictory directionality of these interactions strongly reduces the importance of the buttressing effect in the case of compounds with bulky ortho-substituents, which is most clearly displayed in the absence of any relationship between the size of ortho-substituents and the basicity. On the contrary, for proton sponges having in ortho-positions the electron-donating groups with lesser steric demands, both the buttressing and the polar effects act in the same direction. This is the reason for the exceptionally high basicity of 2,7-dimethoxy- (2) and tetrakis(dimethylamino)- (3a) naphthalenes. It has been found that bis(trimethylsilyl)-bis(dimethylamino)naphthalene 7d has an in-out configuration of the NMe2 groups in the solid that is the first example of its kind in the series of naphthalene proton sponges. The origin of a yellow coloring of 2,7-disubstituted proton sponges is also discussed.     

Complex Formation in the System Bis[2-(trimethylammonio)ethyl] Succinate Diodide-Iodine in Solutions and in Crystal

The complex formation in the system bis[2-(trimethylammonio)ethyl] succinate diodide-iodine involves no more than two iodine molecules. The crystal structure of the salt [(CH3)3N(CH2)2OCOCH2]2(I3)2 is formed by layers of inorganic anions (I₃ ^-) and organic dications (centrosymmetric dications {[(CH₃)₃N · (CH₂)₂OCOCH₂]⁺}₂), evenly alternating along the a axis. The crystal structure of the salt [(CH₃)₃N(CH₂)₂·OCOCH₂]₂(I₃)₂(I₂)0.5 is formed by organic and inorganic layers evenly alternating along the [011] diagonal, with a centrosymmetric iodine molecule.     

Synthesis and Structure of Co(III) Complexes with 2-Pyridinecarboxylic Acid

The Co(III) complexes with pyridinecarboxylic acid, Na[Co(Pc)₂(NO₂)₂] (I) and NH₄[Co(Pc)₂(NO₂)₂] (II), where Pc is the 2-pyridinecarboxylate anion, have been synthesized and studied by X-ray diffraction. In the crystal, the complex anions are combined through the Na⁺ and NH ₄ ⁺ cations. In II, the anion and the cation are combined by hydrogen bonds.     

Heterometallic compounds with the binuclear complex anion [Cr<Subscript>2</Subscript>(OH)(Ac)(Nta)<Subscript>2</Subscript>]<Superscript>2−</Superscript>: Synthesis and structure

Heterometallic compounds BaCr₂(OH)(Ac)(Nta)₂ · 4H₂O (I) and [Fe(L)₃][Cr₂(OH)(Ac)(Nta)₂] · nH₂O (L is Bipy (II) and Phen (III); Bipy is, αα′-bipyridine, Phen is o,o′-phenanthroline, Ac⁻ is acetate ion, Nta is nitrilotriacetate ion; n = 8 (II) and 6.25 (III)) are synthesized. According to the X-ray diffraction data, compounds II and III have ionic structures built of the isolated complex cations [Fe(L)₃]²⁺, binuclear complex anions [Cr₂(OH)(Ac)(Nta)₂]²⁻, and crystallization water molecules. The magnetic properties of compounds II and III in the interval from 2 to 300 K confirm assumptions on the diamagnetic character of [Fe(L)₃]²⁺ and indicate the antiferromagnetic interaction between the chromium atoms in the dimeric fragment [Cr₂(OH)(Ac)(Nta)₂]²⁻.     

Tandem regio- and stereospecific cyclization of ethyl isonicotinate with cyanoacetylenic alcohols to provide novel polycondensed heterocyclic systems

Ethyl isonicotinate reacts with tertiary cyanoacetylenic alcohols under exceptionally mild conditions (room temperature, without catalyst or solvent) to afford novel polycondensed heterocyclic systems, 4,15-dioxa-7,12-diazapentacyclo[9.5.2.0^2,10.0^3,7.0^12,16]octadeca-8,17-dienes, in 30-68% yields. This tandem cyclization is regio- and stereospecific. Despite several asymmetric carbons (up to six) being present in the molecules, only one diastereomer is formed and both cyanomethylidene fragments possess exclusively Z-configuration. The tandem sequence includes the formation of 1,3-oxazolidino-1,2-dihydropyridines which undergo Diels-Alder cyclodimerization to give the final products.     

Crystal and Molecular Structures of 3-Carboxypropyltriphenylphosphonium Diiodobromide

Complexation in the 3-carboxypropyltriphenylphosphonium bromide–molecular iodine system in chloroform was studied. The maximum number of iodine molecules coordinated by 3-carboxypropyltriphenylphosphonium bromide was established by the spectrophotometric method using a function of the average-iodine number, and the stability constant of the complex was determined. The [(C₆H₅)₃P(CH₂)₃COOH]BrI₂ diiodobromide was studied by X-ray diffraction analysis. The characteristic feature of the crystalline salt was the formation of dimer associates: anionic associates were formed due to the Br···Br intermolecular interactions and cationic associates were formed due to the O···H–O hydrogen bonds. The data obtained were correlated to the results of quantum-chemical calculations.