The study of redox reactions of bisarenechromium complexes by the rotating disk electrode technique: I. Oxidation of bisarenechromium(O) complexes and reduction of bisarenechromium(I) cations

The redox properties of twenty bisarenechromium complexes have been studied by the rotating disk electrode technique in an aprotic solvent (DMSO). The half-wave potentials, E_1/2, have been found to correlate well with the meta-substituent constants. The conclusion is drawn that the electronic effects of substituents are mainly transferred to the reaction centre (the metal atom) by the inductive mechanism. The conjugation of substituents with the coordinated ring is weaker in bisarenechromium complexes than in ferrocene derivatives.     

Wirkung von Substituenten und Anionen auf die Fluoreszenzeigenschaften gemischtligandiger (Amin-triphenylphosphan)kupfer(I)-Halogenide

Effect of Substituents and Anions on the Fluorescence Properties of Mixed-Ligand (Amine-triphenylphosphane) Copper(I) Halides Mixed-ligand complexes analyzing CuHal · PΦ₃ · Py? R where Hal = Cl^?, Br^?, I^? and where R are various substituents at the pyridine (Py) exhibit an intense solid state fluorescence depending on substituent and anion when excited with uv radiation (365 nm). It will be shown that there is a relation between fluorescence and mesomeric and inductive properties of substituents and anions.     

13C NMR Spectra of 8-mercaptoquinoline derivatives

The additivity of the effect of the increments of the substituents on the ¹³C chemical shifts in polysubstituted quinolines is demonstrated. In the case of substitution in the pyridine part of quinoline (R = CH₃, OCH₃, SCH₃) the ortho increments are depressed as compared with the increments in benzene derivatives. This is associated with a change in the charge on the ring carbon atom and polarization of the C-H bond because of steric hindrance.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 937–940, July, 1981.     

Infrared study of intramolecular coordination in (chloromethyl)- and (dichloromethyl)-germanes

Frequencies (ν) and integrated intensities (A) of GeH stretching modes in the IR spectra of (diorgano)germanes containing GeCH₂Cl and GeCHCl₂ fragments have been measured. Anomalous values of ν and A (compared to those expected from the inductive effect only) are explained by intramolecular coordination between chlorine and germanium atoms. The enthalpy of intramolecular coordination (ΔH) has been determined by IR spectroscopy. The enthalpy of intramolecular coordination is shown to increase with the acceptor properties of the substituents bonded to the germanium atom in (dorgano)- and (triorgano)-germanes.     

Crystal structure and magnetic properties of the octahedral complexes of Ni(II) with 3-imidazoline nitroxides

This paper reports on our studies of the crystal structures and magnetic properties of five mixed-ligand octahedral complexes of Ni(II) with 3-imidazoline nitroxides Ni(RL)₂X₂, where RL are deprotonated enaminoketone derivatives of 3-imidazoline nitroxide with different substituents R (CF₃, Ph) in the side chain, and X is pyridine, dimethylsulfoxide, or semi-phenanthroline. It is established that this type of heterospin system is characterized by an intramolecular exchange interaction parameter (J) of an order of 10 cm⁻¹. Substitution of the N-donor diamagnetic pyridine or phenanthroline by the O-donor dimethylsulfoxide in the coordination sphere of the metal decreases J by 2–3 cm⁻³. A transition from trans-to cis-coordination of the enaminoketone ligands and variation of the R substituent in the chelate ring do not affect the value of J. Deceased. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 5, pp. 901–916, September–October, 1998. This work was supported by INTAS grant No. 94-3508 and RFFR grants No. 96-03-33738 and 96-03-32229.     

Crystal solvates of carboxy-substituted Zn(II) phthalocyaninates with pyridine

Physicochemical characteristics (composition, energetic and chemical stability) of the molecular complexes of carboxy-substituted Zn(II) phthalocyaninates with pyridine were determined. It was found that the carboxyl substituents in positions 4 and 5 of the complex Zn(4,5-COOH)₈Pc favor the formation of the most stable molecular complexes with pyridine. The carboxyl substituents in the composition of Zn(3-COOH)₄Pc are not solvated with pyridine due to steric hindrances and the formation of the hydrogen bond between the carboxyl H atom and the meso-nitrogen atom; the molecular complexes of a tetrasubstituted Zn(4-COOH)₄Pc with pyridine are unstable.     

Structure of Diacetato bis (2,4,6 Trimethyl Pyridine) Copper(II)

(2.4.6 trimethyl pyridine)₂ Cu(CH₃COO)₂ has been obtained as violet needles by slow evaporation. The crystals belong to the monoclinic system, space group P2_1/C with two molecules in a unit cell of dimension: a = 7.842 (1), b = 16.384 (2), c = 8.320 (2) Å, β = 101.91 (1)°. The structure was solved by heavy atom method and refined by a least squares method (R = 0.029). The coordination of copper is 4 + 2. The atom arrangements of this structure is very near to the copper acetate one solvated by one water molecule and two 3.4 dimethyl pyridine molecules.     

First structural authentication of third-sphere coordination: [p-sulfonatocalix[4]arene]5- as a third-sphere ligand for Eu3+

Abstract

The central feature of the complicated structure of Na[Eu₃(p-sulfonatocalix[4]arene)₂(OH₂)18(ONC₅H₅)₃]·14 H₂O is the coordination sphere of one of the three independent europium atoms. Its first coordination sphere consists of seven water molecules, the oxygen atom of a pyridine N-oxide molecule, and a sulfonate oxygen atom from one of the two independent calix[4]arenes. The second-sphere coordination consists of the second calix[4]arene which is bound to the coordinated pyridine N-oxide via hydrophobic interactions, and a second pyridine N-oxide which is hydrogen bonded to a coordinated water molecule. The third-sphere coordination consists of the binding of the second-sphere coordinated pyridine N-oxide to the cavity of the first-sphere coordinated calix[4]arene. Na[Eu₃(p-sulfonatocalix[4]arene)₂(OH₂)₁₈(ONC₅H₅)₃]·14 H₂O crystallizes in the monoclinic space group P2₁/c with a = 20.973(2), b = 18.678(2), c = 29.502(4)Å, β = 109.19(1)°, and D_c = 1.74 g cm^?3 for Z = 4. Refinement based on 10,043 observed reflections led to a final R value of 0.091.     

The structure of a new copper(II) complex with 3-methyl-5-carboxylatopyrazole

Molecular and crystal structures of a new complex compound of copper(II) with 3-methyl-5-carboxylatopyrazole (CH₃PzCOO^?) with the composition Cu(CH₃PzCOO)₂·H₂O have been determined by single crystal XRD. It has been demonstrated that the carboxylate ion performs the bridging tridentate function. In the equatorial plane coordination occurs through the pyridine N atom of the pyrazole and one of O atoms of the carboxylate group yielding a five-membered metallocycle CuNOC₂. The second O atom of one of the ligands is bound to the neighboring copper(II) ion affording an infinite linear chain. The coordination polyhedron of the copper atom is a square pyramid, coordination core CuN₂O₃.     

Efficient asymmetric addition of diethylzinc to aldehydes using C2‐novel chiral pyridine β‐amino alcohols as chiral ligands

A series of novel C₂‐symmetric chiral pyridine β‐amino alcohol ligands have been synthesized from 2,6‐pyridine dicarboxaldehyde, m‐phthalaldehyde and chiral β‐amino alcohols through a two‐step reaction. All their structures were characterized by ¹H NMR, ¹³C NMR and IR. Their enantioselective induction behaviors were examined under different conditions such as the structure of the ligands, reaction temperature, solvent, reaction time and catalytic amount. The results show that the corresponding chiral secondary alcohols can be obtained with high yields and moderate to good enantiomeric excess. The best result, up to 89% ee, was obtained when the ligand 3c (2S,2′R)‐2,2′‐((pyridine‐2,6‐diylbis(methylene))bisazanediyl))bis(4‐methyl‐1,1‐diphenylpentan‐1‐ol) was used in toluene at room temperature. The ligand 3g (2S,2′R)‐2,2′‐((1,3‐phenylenebis(methylene))bis(azanediyl))bis(4‐methyl‐1,1‐diphenylpentan‐1‐ol) was prepared in which the pyridine ring was replaced by the benzene ring compared to 3c in order to illustrate the unique role of the N atom in the pyridine ring in the inductive reaction. The results indicate that the coordination of the N atom of the pyridine ring is essential in the asymmetric induction reaction. Copyright © 2014 John Wiley & Sons, Ltd.     

Reactions of polyhalopyridines 5. Reaction of 2,3,5,6-tetrachloro-4-trifluoromethylthiopyridine with nucleophilic reagents

The reaction on 2, 3, 3, 6-tetrachloro-4-trifluoromethylthiopyridine with various nucleophilic reagents has been studied. It was shown that the CF₃S group is readily replaced under the action of O- and S-nucleophiles. Competition was detected between replacement of an a-chlorine atom on the pyridine ring and of the fluorinecontaining group under the action of N-nucleophilic reagents. New derivatives of trichlorotrifluoromethylthiopyridine with nitrogen-containing substituents have been synthesized.For Communication 4 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 63–67, January, 1994.     

The binding energy of nitrogen 1<Emphasis Type="Italic">s</Emphasis> electrons in pyridine derivatives: Substituent effects in N-centered radical cations

The effect of substituents on the binding energy of nitrogen 1s electrons in 2-, 3-, and 4-substituted pyridine derivatives, as measured by X-ray photoelectron spectroscopy and calculated by quantum chemistry methods, was analyzed. It has been first shown that the binding energy depends not only on the inductive and resonance effects, but also on the polarization effect of the substituents.     

On the Search of Metallated Sulfonamides: Synthesis and X‐ray Characterization of the New Sulfathiazolato Nickel(II)‐Chelate Complex [Ni(STZ)2(Py)2]·2Py (STZ = Sulfathiazolato Anion; Sulfathiazole = N1‐2‐thiazolyl‐sulfanilamide; Py = Pyridine)

Sulfathiazole (HSTZ) reacts with triethylamine and Ni(CH₃COO)₂·4H₂O in methanol and further with pyridine to give the sulfathiazolato complex [Ni(STZ)₂(Py)₂]·2Py. In the new chelate complex the deprotonated sulfonamidic nitrogen atom does not take part in the coordination process, apparently retaining the negative charge. Two (STZ)^? moieties are symmetrically bonded to the Ni²⁺ ion through a thiazolyl nitrogen atom and an oxygen atom of the S(O)₂ group. Two pyridine molecules accomplish the fairly distorted octahedral coordination at the metal centre.     

From Osmium Hydrido Vinylidene to Osmacycles: The Key Role of Osmabutadiene Intermediates

Osmium hydrido vinylidene 1 shows diverse cyclization reactivity with activated terminal alkynes. Treatment of 1 with HC?CCOR′ (R′=OEt and Me) gave osmafurans 3 a and 3 b via osmium alkenyl/vinylidenes 2 a and 2 b . In addition, 1 reacted with HC?CCH(OH)C?CH to yield osmabenzene 4 , in which the alkynol acted as a C₅ fragment to cyclize with 1 . Mechanistic analysis indicates that these reactions and the previous formal [3+3] cycloadditions between 1 and HC?CCH(OH)R (R=Ph, Et, and vinyl) or HC?CCH(OEt)₂ all go through similar osmabutadiene intermediates. Subsequently, the intermediates either took a “coordination and cyclization” process or a “carbon–carbon coupling” path to cyclization, depending on the coordination ability of substituents on the terminal alkenyl carbon atom.     

Mass-spectrometric study of 4-azaphenanthrene derivatives

The mass spectra of 15 compounds of the 4-azaphenanthrene series and their deutero analogs with bulky R substituents (R=-CCPh, -CH=CHPh, CHBr-CHBrPh,-CH=CHC₆H₄OCH₃-p, -COOH, -COOC₂H₅, and -CONHNH₂) in the ortho position relative to the nitrogen atom were studied. An intense [M-H]⁺ ion peak, the appearance of which is evidently due to a process involving cyclization of the carbon atom of the side chain with the nitrogen atom, is formed in the fragmentation of the styryl derivatives. The fragmentation of the compounds with a methyl group in the ortho position relative to the styryl grouping is accompanied by the formation of an intense [M-Ph]⁺ ion peak. An ortho effect of the carboxyl and carbethoxy groups adjacent to the methyl substituent is observed in the mass spectra of the investigated compounds. The data obtained make it possible to establish the structures of bulky substituents in the ortho position relative to the ring nitrogen atom and the position of the methyl group in the pyridine ring of monomethylated azaphenahthrenes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 659–665, May, 1979.     

Substituted pyridine coordinated N,N-trans and N,N-cis cyclopalladated complexes of (S)-4-tert-butyl-2-phenyl-2-oxazoline: Crystal structures, spectral study and catalysis of the decomposition of PS pesticides

Three pyridine coordinated cyclopalladated complexes: (S)-chloro{2-[2-(4-tert-butyl)oxazolinyl]phenyl-C,N}(4-R-pyridine)palladium(II) (R = H, 2; R = CF₃, 3; R = NMe₂, 4), have been synthesized and structurally characterized. While the crystal structure shows that 2 has a normal N,N-trans-conformation in the coordination sphere of palladium(II), 3 and 4 exhibit uncommon N,N-cis-conformations. From ¹H NMR measurements, the major coordination isomer in deuterated chloroform solution is N,N-trans configuration for three palladacycles. It was found that the three complexes catalyze effectively the methanolysis of the PS pesticides including chiral thiophosphates but show different activity depending on the substituents of co-coordinated pyridine ring in 2–4.     

A F NMR study of steric hindrance and intramolecular coordination in organo-mercury, -tin and -lead derivatives of 2,6-dimethyl-4-fluorothiophenol and 2,6-dibromo-4-fluorothiophenol

Some organomercury, -tin and -lead derivatives of 2,6-dimethyl-4-fluorothiophenol and 2,6-dibromo-4-fluorothiophenol of the general type R_pMSAr have been prepared. The fluorine chemical shifts of the compounds realtive to internal fluorobenzene and the ¹⁹F SCS values for the corresponding substituents have been determined and discussed in terms of steric hindrance and intramolecular coordination, the behaviour of the organometallic substituents R_nMS in these respects being compared with that of the SH and CH₃S groups. The anomalously low steric requirements of R_nMS groups, as well as the differences in the strength of intramolecular coordination and its influence on the acceptor power of the metal atom, in the compouds of mercury, tin and lead have been demonstrated.     

Synthesis of new charge-compensated cobalt bis(1,2-dicarbollide) derivatives

New hetero-substituted charge-compensated cobalt bis(1,2-dicarbollide) derivatives were synthesized by the reaction of 8,8′-μ-iodo-3-commo-3-cobalta-bis(1,2-dicarba-closo-dodecaborane) [8,8′-μ-I-3,3′-Co(1,2-C₂B₉H₁₀)₂] with 1,4-thioxane, pyridine N-oxide, and tetrahydropyran. X-ray diffraction studies showed that the 8′-iodo-8-(pyridiniumoxy)eucosahydro-1,1′,2,2′-tetracarba-3-commo-cobalta-closo-tricosaborate molecule has the gauche-conformation (the substituents are turned with respect to each other by 69.2°). The positive charge is predominantly localized on the N(Py) atom.     

Polar Effects in the Solvolysis of 4-Substituted Bicyclo [2.2.2]octyl p-Nitrobenzenesulfonates. Polar effects. VII

Hydrolysis of bicyclo[2.2.2]octylp-nitrobenzenesulfonate ( 14a , X = p-NO₂C₆H₄SO₃), and nineteen 4-R-substituted derivatives 14b–14t in 70% aqueous dioxane yield the corresponding bicyclo[2.2.2]octanols 14 (X = OH), exclusively. The 7-center fragmentation to 1,4-dimethylidene-cyclohexane ( 15 ) is not observed. The logarithms of most of the rate constants, measured in 80% ethanol, correlate well with the corresponding inductive substituent constants σ of R. Hence, in these cases ionization rate is controlled by the inductive effect of R only. Poor correlations result when the substituents are potentially electrofugal groups, such as COO^?, CH₂OH, CH₂NH₂, CONH₂ and H, the deviations from the inductive regression line corresponding to rate enhancements of 1.6 to 8. These exalted substituent effects are tentatively ascribed to extended hyperconjugation involving two σ-bonds. This study corroborates previous evidence that the inductive effect alone does not fully account for the polar effect of some substituents in reactions involving carbocations.     

Nickel-mediated cross-coupling via C–O activation assisted by organoaluminum

We report the alkylation and arylation cross-coupling of aryl ethers based on C–O bond activation using a nickel catalyst and organoaluminum reagents. Ni(cod)₂ in combination with 1,2-bis(dicyclohexylphosphino)ethane ligand in toluene solution at 130°C are the best conditions. The naphthyl ether or methoxy pyridine derivatives are suitable substrates for alkylation and arylation reaction with a wider scope of aluminum reagents in good yields. Computational analysis on the pyridine substrate is provided to help delineate the mechanistic pathway and demonstrate the important aspects of the cooperative interaction bimetallic catalysis. First, the coordination of AlMe₃ to the O atom of pyridine is essential for C–O activation. Second, the β-H transfer from methoxy to pyridine could be discouraged through the use of bidentate phosphine as a ligand. Finally, excess AlMe₃ reagent is critical for facilitating a reductive elimination process.