New basicity/nucleophilicity scale on the basis of parameters of formation of axial <Emphasis Type="Italic">n</Emphasis>,ν-complexes derived from tetraphenylporphyrinatozinc(II) and base/nucleophile as ligand

The stability constants of complexes derived from tetraphenylporphyrinatozinc(II) and various ligands in chloroform at 25°C were proposed as nucleophilicity/basicity parameters of the latter, which reflect the effects of electronic and steric factors. Supernucleophilicity of heteroaromatic N-oxides in reactions with electrophiles was interpreted in terms of sp ²–sp ³ rehybridization of the N-oxide oxygen atom.     

Change in the hybridization of the N→O group oxygen atom upon complex formation of pyridine and quinoline <Emphasis Type="Italic">N</Emphasis>-oxides with v-acceptors

It was shown on the basis of X-ray structural and NMR data that the (sp ²→sp ³) rehybridization of the oxygen atom of the N→O group can take place in reactions of heteroaromatic N-oxides with Lewis and Bronsted-Lowry acids. The hybridization type depends on the ligand and acceptor natures, composition of a complex, and spatial stresses arising during the complex formation.     

Thermooxidative decomposition of heterocyclic <Emphasis Type="Italic">N</Emphasis>-oxides

Thermooxidative decomposition of pyridine N-oxide, 4-(4-dimethylaminostyryl)pyridine N-oxide, 4-(4-methoxystyryl)pyridine N-oxide, quinoline N-oxide, 2-methylquinoline N-oxide, 4-chloroquinoline N-oxide, 2-styrylquinoline N-oxide, and 2-(4-dimethylaminostyryl)quinoline N-oxide was studied. The kinetic parameters of the thermooxidative processes were calculated according to three independent procedures. The relation between the nature of heterocyclic N-oxide and its stability to thermal oxidation was analyzed.     

Thermal behavior of quinoline <Emphasis Type="Italic">N</Emphasis>-oxide hydrates and deuterohydrate

Spectral and thermochemical investigation of physicochemical properties of quinoline N-oxide crystallohydrates with H₂O and D₂O is carried out. Quinoline N-oxide is established to form with H₂O a stable dihydrate where two water molecules are energetically not equal. Complete dehydration of quinoline N-oxide occurs when temperature reaches 150°C. With accounting for the obtained thermochenical data, quinoline N-oxide and its mono- and dihydrates are isolated in the individual state and their IR spectra are registered and considered. It is established that at boiling quinoline N-oxide in D₂O proceeds chemical reaction affording isoindoline-1,3-dione (phthalimide). The product is identified by elemental analysis and ¹H NMR and IR spectroscopy. The band assignment in the IR spectra of quinoline N-oxide, phthalimide and of the complex of the latter with D₂O is based on the quantum-chemical DFT calculations.     

Complexes of pyridine and quinoline N-oxides with boron trifluoride: the <Superscript>1</Superscript>H NMR study

The formation of complexes of pyridine and quinoline N-oxides with BF₃ was studied by ¹H NMR method. It was shown that the molecular complexes obtained are either individual isomers or a mixture of stereoisomers, whose structures are determined by both electronic and steric properties of substituents in a heterocycle. The type of hybridization (sp3 or sp2) of the O atom of the N-oxide group in the above adducts was assumed to be specified also by the above factors.     

Molecular complexes of 4-nitropyridine and 4-nitroquinoline <Emphasis Type="Italic">N</Emphasis>-oxides with boron trifluoride and hydrogen chloride as intermediates in S<Subscript>N</Subscript>Ar reactions

Complexation of 4-nitropyridine N-oxides with ν- (BF₃, HCl) and π-acceptors (tetracyanoethylene, chloranil, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, 7,7,8,8-tetracyanoquinodimethane) activates the nitro group to nucleophilic replacement by chlorine. Adducts formed by 4-nitropyridine and 4-nitroquinoline N-oxides with boron trifluoride and hydrogen chloride were studied by IR spectroscopy. It was shown that these complexes belong to the n,ν type and that the donor-acceptor interaction therein involves the oxygen atom of the N-oxide group.     

Influence of the methylene group between azadithiolate nitrogen atom and phenyl moiety on the protophilic properties of [FeFe]-hydrogenase model complexes

An [FeFe]-hydrogenase mimic 4 with functional benzyl moiety covalently linked to the azadithiolate ligand was synthesized. The structure, protonation, and electrochemical properties of 4 and a phenyl substituted analogue (coded as 3) were simultaneously studied to explore the influence of the methylene group between the bridgehead nitrogen atom and functional phenyl moiety on the protophilic properties of the model complexes. X-ray single crystal diffraction analysis revealed that the nitrogen atoms of 3 and 4 possessed sp ² and sp ³-hybridization, respectively. Although the light-driven electron transfer was prevented in the molecule of 4, the sp ³-hybridized nitrogen atom of 4 could be protonated in the presence of the proton acid to give the [4(NH)]⁺ cation. The generated positive charge could be reduced at ca. ?1.2 V versus Fc/Fc⁺ with a distinctly electrocatalytic proton reduction activity, whereas the proton reduction catalysed by 3 occurred at ca. ?1.45 V. The catalytic proton reductions of 3 and 4 followed ECCE and CECE mechanisms, respectively. It was noteworthy that the potential of 4 was remarkably anodic shifted and closer to that of the proton reduction catalysed by natural enzymes.     

Structural features of the phosphorus heterocumulene ylides (<Emphasis Type="Italic">sp</Emphasis>-ylides)

The features in phosphorus heterocumulene yilides Ph₃PCCX [X = NPh, NC(O)Ph, C(CN)CO · (OMe), O, S] with the ylide carbon geometry close to sp-hybridization are studied using ab initio methods. Estimation of structural parameters of a new member in the Ph₃PC^α=C^β=NC(O)Ph series on the B3LYP/6-31G(d,p) level and together with experimental data for related ylide (X = NPh) gave the following values: r(PC^α) 1.665 Å, r(C^α=C^β) 1.237 Å, ω(PC^αC^β) 145.2°. Nonvalent interactions of sp ^λ orbital of the ylide carbon atom bearing extra negative charge with coplanar π-electrons of the nearest C^β=N bond are found close to those of nitrogen lone pair with the C^α=C^β bond and leading to up to 10° nonlinearity of C^α-C^β=N triad of the phosphorus iminoketene ylides. Chemical nonequivalence of the PC^ipso bonds in the triphenylphosphonium fragment, relation of \(^1 J_{PC^\alpha } \) spin-spin coupling and antisymmetric bonding vibration ν^as(C=C=X) to the structure of the carbanion, and inductive hyperconjugative influence of atom (or group) X on the ylide carbon geometry are discussed.     

Synthesis and structure of silicon-containing <Emphasis Type="Italic">N</Emphasis>-methyland <Emphasis Type="Italic">N</Emphasis>-benzoylamides of diisopropylphosphoric acid

Diisopropyl N-benzoyl-N-(trimethylsilyl)phosphoramidate reacts with ClCH₂SiMe₂Cl under mild conditions to form diisopropyl N-benzoyl-N-[(chlorodimethylsilyl)methyl]phosphoramidate (III). Diisopropyl N-methyl-N-(trimethylsilyl)phosphoramidate with ClCH₂SiMe₂Cl affords an N-transsilylation product which does not rearrange into diisopropyl N-[(chlorodimethylsilyl)methyl]-N-methylphosphoramidate (XV) even under severe conditions (4 h, 130°C). Compound XV was prepared by the reaction of diisopropyl phosphorochloridate with N-[(methoxydimethylsilyl)methyl]-N-methylamine followed by treatment of diisopropyl N-[(methoxydimethylsilyl)methyl]-N-methylphosphoramidate with boron trichloride. Analysis of experimental and calculated ²⁹Si chemical shifts points to a five-coordinate silicon atom in compound III and a fourcoordinate silicon atom in compound XV. According to B3LYP calculations with due regard to solvent effects, compound III is an isomer with a C=O→Si bond. By variation of substituents at silicon, phosphorus, and carbonyl carbon atoms, chelate structures with either C=O→Si or P=O→Si dative bonds can be obtained.     

Coordination compounds of CuCl<Subscript>2</Subscript> with 1-(<Emphasis Type="Italic">N</Emphasis>-heterylmethyl)silatranes

Reactions of CuCl₂ with 1-(N-indolylmethyl)and 1-(N-carbazolylmethyl)silatranes (L) afforded new complexes CuCl2?L. Quantum chemical calculations of these complexes and a Cu^II complex with 1-(N-pyrrolylmethyl)silatrane showed that the Cu atom is coordinated to both the equatorial O atom of the silatranyl group and the π-system of the ligand? heterocycle.     

Synthesis and Structure of Bis(Ethylenediamine-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Di-3-Propionato)Zinc Dihydrate

Bis(ethylenediamine-N,N-di-3-propionato)zinc dihydrate [Zn(EDDP)]₂ ? 2H₂O is prepared from dichloro(ethylenediamine-N,N-di-3-propionato)zinc in the presence of silver(I) oxide. The prepared complex is studied by X-ray diffraction and spectroscopic methods. A molecule of the complex has a centrosymmetric dimeric structure. Zn atoms have trigonal-bipyramidal coordination formed by the nitrogen atoms of primary and tertiary amino groups, two oxygen atoms of propionic groups of one EDDP molecule, and one oxygen atom of the other.     

Diphenylguanidinium (ethylenediaminetetraacetato)hydroxogermanate hydrate (HDphg)[Ge(OH)(Edta)] · H<Subscript>2</Subscript>O: Synthesis,physicochemical characterization,and crystal structure

The onium compound based on the germanium(IV) complex with ethylenediamine-N,N,N ¹,N ¹-tetraacetic acid (H₄Edta) and diphenylguanidine (Dphg), (HDphg)[Ge(OH)(Edta)] · H₂O, has been isolated in the solid state and studied by physicochemical methods. Its crystal structure has been determined by the X-ray diffraction method. The crystals are monoclinic, a = 7.0179(9) Å, b = 28.797(8) Å, c = 13.477(2) Å, β = 104.301(12)°, V = 2639.3(9) Å₃, Z = 4, space group P2₁/c, R = 0.045 for 2524 reflections with I > 2σ(I). The onium compound is built of diphenylguanidinium cations HDphg⁺, [Ge(OH)(Edta)]^? anions, and water molecules of crystallization. In the complex anion, the Ge atom is coordinated by two nitrogen atoms and three oxygen atoms of three acetate arms of the pentadentate chelating ligand Edta^4? (av. Ge-N, 2.095(4) Å; Ge-O, 1.891(3) Å). The fourth acetate arm is deprotonated and is not involved in coordination with the metal. The coordination of the metal atom is completed to an octahedral one by the O atom of the hydroxo ligand (Ge-OH 1.759(3) Å). The structural units in crystal are linked by a system of hydrogen bonds.     

Reaction of thiourea and substituted thioureas with 1,3-dibromopropyne

4-Bromomethylidene-2-imino(phenylimino, acetylimino)-1,3-thiazolidine hydrobromides and 4-bromomethylidene-2-acetylimino-1,3-thiazolidine are synthesized by the reaction of thiourea, N-phenylthiourea, N,N′-diphenylthiourea and N-acetylthiourea with 1,3-dibromopropyne in glacial acetic acid, absolute methanol, acetonitrile at 20°C or upon heating (60°C).     

New binuclear <Emphasis Type="Italic">bis</Emphasis>(2,4,6,8-tetramethyl-2,4,6,8-tetraazobicyclo(3.3.0)octane-3,7-dione-<Emphasis Type="Italic">O,O</Emphasis>')-tetraaqua-hexakis(nitrato-<Emphasis Type="Italic">O,O</Emphasis>')-disamarium(III) complex: Synthesis and crystal structure

The centrosymmetric binuclear complex of samarium(III) nitrate with bicyclic biscarbamide 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar (Mk) namely, [Sm(C₈H₁₄N₄O₂)(H₂O)₂(NO₃)₃]₂ (I) has been synthesized. Its crystal structure has been characterized (CIF file CCDC no. 1451436). Crystals of complex I are triclinic, space group P1 a = 9.8661(2) Å, b = 10.2913(3) Å, c = 10.9629(3) Å, α = 74.475(2)°, β = 67.802(2)°, γ = 67.570(2)°, V = 942.68(5) ų, ρcalcd = 2.01028 g/cm³, and Z = 1. The samarium atom is coordinated by the two oxygen atoms of two Mk molecules bonded via the symmetry center, three bidentate nitrate anions, and two water molecules. The coordination number of the samarium atom is 10, the coordination polyhedron of the metal atom is a decahedron and the Sm…Sm distance is 9.7904(4) Å.     

Reaction of 2-methylquinoline with 3-phenylprop-2-ynenitrile in the KOH—H<Subscript>2</Subscript>O system

The reaction of 2-methylquinoline with 3-phenylprop-2-ynenitrile in the presence of water (0—25 °C, 20 mol.% KOH, 5 equiv. H₂O) is accompanied by the loss of aromaticity of the quinoline nucleus and results in double functionalization of the molecule at the nitrogen atom and the methyl group. Two 2-cyano-1-phenylethenyl groups were introduced into the molecule to form (2E,4E)-4-{1-[(Z)-2-cyano-1-phenylethenyl]quinolin-2(1H)-ylidene}-3-phenylbut-2-enenitrile in 59—67% yield. This reaction is stereoselective: the N-2-cyano-1-phenylethenyl-substituent has the Z-configuration, while the 1,3-diene moiety at the methyl group has the E,E-configuration. (2E)-3-Phenyl-4-(quinolin-2-yl)but-2-enenitrile that formed as a by-product (0—24% yields) is formally the addition product of the methyl group of the quinoline substrate at the acetylenic bond.     

Crystal structure of the complex of copper(II) with 3-(2-hydroxy-3-sulfo-5-nitrophenylazo)-pentadione-2,4

A new complex of copper (II) with 3-(2-hydroxy-3-sulfo-5-nitrophenylazo)-pentadione-2,4 (HL) is synthesized and analyzed by single crystal XRD. The crystals are monoclinic: a = 7.7563(4) Å, b = 24.0157(12) Å, c = 24.6353(13) Å, β = 91.9490(10)°, V = 4586.2(4) ų, space group P2₁/c, Z = 2, ρ_calc = 1.713 g/cm³, R = 0.0695. The environment of the copper atom is formed by three oxygen atoms, the nitrogen atom of tetradentate ligand, and the oxygen atom of a water molecule.     

7,8,9-trimethyl-1-phenyl-3<Emphasis Type="Italic">H</Emphasis>-pyrrolo[2,1-<Emphasis Type="Italic">d</Emphasis>][1,2,5]triazepin-4(5<Emphasis Type="Italic">H</Emphasis>)-one. Synthesis and reactions

A strategy was developed for the synthesis of 7,8,9-trimethyl-1-phenyl-3H-pyrrolo[2,1-d][1,2,5]-triazepin-4(5H)-one, reactions of its functionalization at the С⁴ atom and aza rings fusion at the С⁴?N³ bond were explored. The formation mechanism of the pyrrolo-1,2,5-triazepinone scaffold was suggested.     

Splitting of the <Emphasis Type="Italic">d</Emphasis><Superscript><Emphasis Type="Italic">N</Emphasis></Superscript> atomic states in icosahedral 3<Emphasis Type="Italic">d</Emphasis> metal endofullerenes M@C<Subscript>60</Subscript>

Group-theoretical and quantum-chemical investigations of the spectrum of low-lying excited states have been performed by the ROHF and FCI-RAS (Full CI in Restricted Active Space) methods for 3d metal endofullerenes (MEFs) M@C₆₀ (M =Mn, Cr, and Fe) in different charged states. The major purpose of this study is quantum-chemical verification of the anomalous (“non-Bethe’s”) character of splitting of the d ^N atomic states in an electrostatic field with icosahedral symmetry, predicted previously within the theory of integral invariants theory. The interrelation between the integral invariants theory and the quantumchemical methods applied in this work is considered in detail. Our calculations suggest that the d ^N atomic states in the icosahedral field generated by fullerene C60 (I _h ) on a metal atom (ion) remain non-split for different charged states of the metal and C₆₀. Reasons for this phenomenon and other possible approaches to verification of the prediction are discussed. It is demonstrated that the d ^N states of the encapsulated metal are split in icosahedral 3d MEFs only under very strong compression of these structures.     

2-amino-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines: Synthesis and reactions with electrophilic reagents

The hydrogenation of 2-amino-5-R-7-R′-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines with NaBH₄ led to the formation of 2-amino-5-R-7-R′-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidines. Acylation, sulfonylation, and alkylation of these compounds depending on conditions and the reagent character occur at the amino group, atoms N³ or N⁴. The treatment with alkali of 2-amino-3-benzyl-5-R-7-R′-4,5,6,7-tetrahydro-1,2,4-triazolo-[1,5-a]pyrimidinium bromide resulted in 2-amino-3-benzyl-5-R-7-R′-3,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]-pyrimidine, similar reaction of 2-acetamido-3-benzyl-5-R-7-R′-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]-pyrimidinium bromide gave a mesoionic product of a hydrogen elimination from the amide nitrogen atom.     

Synthesis and structure of coordination polymer compounds of AgReO<Subscript>4</Subscript> and AgPF<Subscript>6</Subscript> with piperazine

Coordination polymers [Ag(C₄H₁₀N₂)]ReO₄ (I) and [Ag(C₄H₁₀N₂)]PF₆ (II) (C₄H₁₀N₂ is piperazine, Ppz) were synthesized and their structures were determined. Crystals of compound I are monoclinic, space group P2₁/c, a = 6.207(1) Å, b = 12.533(1) Å, c = 11.386(1) Å, β = 93.41(1)°, V = 884.2(2) ų, ρ_calc = 3.337 g/cm³, Z = 4. Crystals of II are monoclinic, space group C2/m, a = 8.723(1) Å, b = 9.083(1) Å, c = 5.797(1) Å, β = 95.07(1)°, V = 457.5(1) ų, ρ_calc = 2.548 g/cm³, Z = 2. Structure I contains polymer chains [Ag(Ppz)] _∞ ⁺ . The silver atom is linked with two nitrogen atoms of the adjacent Ppz ligands to form a nearly linear fragment; the Ag-N_av distance is 2.173 Å, and the NAgN angle is 169.4(3)°. The chains are linked with each other by weak interactions Ag…O(ReO₄) (2.643(8) Å) and N-H…O hydrogen bonds. The structure of compound II also contains cationic polymer chains [Ag(Ppz)] _∞ ⁺ . The Ag⁺ ion is located in the inversion center and has a linear coordination (Ag-N distance is 2.171(9) Å). The central P atom of the octahedral fluorophos-phate ion is also located in the inversion center; the anion is slightly distorted and has no contacts with silver ions at a distance <3.4 Å.