ESR spectroscopic investigation of steric and polar factors in the addition of radicals to unsaturated compounds

The rate constants of the addition of CCl₃CH₂ClCH₃(R⁶) radicals to -methyl-styrene, styrene, methyl methacrylate, methyl acrylate, and acrylonitrile and of CCl₃CH₂(CH₃)₂(R⁷) radicals to styrene, methyl acrylate, and acrylonitrile were determined by ESR spectroscopy. It was shown that the radicals R⁶ and R⁷ possess approximately equal reactivity in addition to unsaturated compounds, despite the difference in the donor-acceptor properties of the substituents at the vinyl group. In a comparison of the reactivity of radicals R⁶ and R⁷ with the reactivity of radicals CCl₃CH₂H₂(R¹), CCl₃CH₂HCH₃(R³), CCl₃CH₂HCl(R⁴), and ClCH₂CH₂Cl₂(R⁵) [1] in addition reactions, it was shown that polar and steric effects of the substituents situated in the -position to the radical site of the above-mentioned radicals, as well as the donor-acceptor properties of the substituents at the vinyl group in the unsaturated compounds, lead to appreciable changes in reactivity.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 136–141, January, 1992.     

Asymmetric PhCH(CH3)CH2OOOOC(CH3)2Ph Tetroxide as an Intermediate in Chain-Termination Processes and Chemiluminescence Excitation in the Oxidation of Cumene

The process of chain termination in the oxidation of cumene was studied. With the use of the semiempirical PM3 method, the structures of primary and tertiary peroxide radicals (PhCH(CH₃)CH₂OO^· and Ph(CH₃)₂COO^·), the PhCH(CH₃)CH₂OOOOC(CH₃)₂Ph tetroxide (TO) (the product of the combination of the above radicals), and TO decomposition products were studied and their heats of formation (H ⁰ _f) were determined; the activation energy of TO decomposition was evaluated. Similar values of H ⁰ _f were obtained by the thermochemical method of group additivity. The PM3 calculation demonstrated that the irreversible decomposition of the asymmetric TO in a six-membered transition complex into the PhCH(CH₃)CHO aldehyde, the Ph(CH₃)COH alcohol, and O₂ is a synchronous process: dramatic changes in the bond lengths and bond orders occurred simultaneously. In this case, 100 kcal/mol was released, which is sufficient for the chemiexcitation of triplet R_–H=O and singlet O₂. A conclusion was drawn that a small impurity of PhCH(CH₃)CH₂OO^· primary radicals plays an important role in chain termination and is the only reason for the excitation of chemiluminescence.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.     

Kristallstruktur von Trimethylisocyanursäure, (CH3NCO)3, und von Trichlorisocyanursäure-1/2-Ethylenchlorid, (ClNCO)3·1/2C2H4Cl2

X-ray crystal structure analyses of (CH₃NCO)₃ (M) and (ClNCO)₃·1/2C₂H₄Cl₂ (C) were carried out at room temperature (MoK, graphite monochromator, =0.71069 Å): 1.M=171.16, monochlinic, P2₁/c,a=14.848 (1) Å,b=13.400 (2) Å,c=8.149 (1) Å, =100.87 (1)°,V=1 592.3 ų,Z=8,F(000)=720,d _x =1.428 Mgm^–3, =76m^–1,R=6.51%,R _w =7.01% (964 reflections, 218 parameters). 2.M=281.89, monochlinic, P 2₁/c,a=9.416 (3) Å,b=5.728 (1) Å,c=18.199 (8) Å, =98.64 (2)°,V=970.4 Å₃,Z=4,F(000)=556,d _x =1.929 Mgm^–3, =1.11 mm^–1,R=3.96%,R _w =3.44% (605 reflections, 132 parameters). The ring systems together with the C atoms of the methyl groups in (M) and with the Cl atoms in (C) are planar and have D_3h-symmetry. Bond lengths and bond angles are discussed with regard to¹⁴N-NQR,³⁵Cl-NQR and vibrational spectroscopic data.

     

Ein einfacher Weg zu α-substituierten (E)-3-Oxo-1-alkenylphosphonsäureestern

Zusammenfassung -Substituierte -Acylvinylphosphonate3 mitE-Konfiguration [R ²CO-CH=C(R ¹)-P(O)(OR)₂], werden in guten Ausbeuten durchWittig-Reaktion von Acylphosphonsäureestern1 [R ¹CO-P(O)(OR)₂,R ¹=Alkyl oder Aryl] mit (2-Oxoalkyliden)triphenylphosphoranen2 [R ²CO-CH=PPh ₃,R ²=Alkyl, O-Alkyl oder CH₂ X (X=Br, OMe, CO₂ Et)] erhalten.

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A convenient route to -substituted dialkyl (E)-3-oxo-1-alkenylphosphonates

-Substituted dialkyl (E)--acylvinylphosphonates [R ²CO-CH=C(R ¹)-P(O)(OR)₂,3], are easily obtained in good yields byWittig-reaction of dialkyl acylphosphonates1 [R ¹CO-P(O)(OR)₂,R ¹=alkyl or aryl) with 2-oxoalkylidene triphenylphosphoranes2 [R ²CO-CH=PPh ₃,R ²=alkyl, O-alkyl and CH₂ X (X=Br, OMe, CO₂ Et)].

     

The kinetics of base hydrolysis of [Co(trien)(amine)Cl]2+ complexes (amine=imidazole,pyridine,n-butylamine and 2,2-dimethoxyethylamine)

Summary The complexescis--[Co(trien)(ImH)Cl]²⁺ (ImH=imidazole, trien=1,8-diamino-3,6-diazaoctane),cis--[Co(trien)(Buⁿ-NH₂)Cl^–]²⁺,cis--[Co(trien)(NH₂CH₂-CH(OMe)₂)Cl^–]²⁺ andcis-₂-[Co(trien)(py)Cl]²⁺ (py=pyridine) have been characterised and their kinetics of base hydrolysis studied. Thecis--isomers which have afac-fac arrangement of the trien ligand have values of k _OH ²⁵ in the 73 to 253 dm³ mol^–1 s^–1 range at I=0.1 mol dm^–3. Extremely rapid base hydrolysis is observed withcis-₂-[Co(trien)(py)Cl]²⁺ where k _OH ²⁵ is 6.65×10⁶ mol³ mol^–1 s^–1 at I=0.1 mol dm^–3. This complex has amer-fac arrangement of the trien ligand with flatsec-NH donor leading to rapid base hydrolysis due to good -overlap between the conjugate base and cobalt(III). The pyridine ligand causes aca. 30 fold rate increase compared with the hydrolysis ofcis-₂-[Co(trien)(NH₃)Cl]²⁺.     

Preparation and structure of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 3-amino-5-(α/β)pyridyl-1, 2, 4-triazoles

Summary Complexes of bidentate 3-amino-5-()-pyridyl-1,2,4-triazole (L¹) and 3-amino-5-()-pyridyl-1, 2, 4-triazole (L²) of composition [ML¹Cl₂·H₂O], [ML²Cl₂·H₂O], [ML ₃ ^2/1 Cl₂] and [ML ₃ ^2/2 Cl₂] [M=Co^II, Ni^II, Cu^II, M=Zn^II] have been prepared and characterized by elemental analyses, i.r., u.v./visible, e.s.r. spectra, magnetic moments and molar conductances.     

Tetraethylammonium acetate tetrahydrate, (C2H5)4N+ CH3COO− · 4H2O,a layer structure with cations sandwiched between nets of puckered polygons formed by hydrogen-bonded anions and water molecules

Crystals of (C₂H₅)₄N⁺ CH₃COOO^– · 4H₂O crystallize in space groupP , witha=12.327(2),b=17.196(6),c=8.753(3) Å, =94.28(2), =91.09(2), =120.30(2)°, andZ=4. The structure was solved by direct methods and refined toR _F -0.060 for 4803 MoK data. In the crystal structure, ordered (C₂H₅)₄N⁺ cations are sandwiched between puckered layers of hydrogen-bonded water molecules and acetate anions. Each wateranion layer is constructed from an edge-sharing assembly of six independent, irregular, and non-planar polygons (two nonagons, two hexagons and two pentagons). All protons in the scheme of hydrogen bonding are uniquely located. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82036 (33 pages).Dedicated to Professor G. A. Jeffrey on the occasion of his retirement.     

Electron spin resonance of Mn2+ ions in matrices of polycrystalline samples of Zn4O[(CH3)2CHCOO]6 and Zn4O[(CH3)3CCOO]3

The ESR spectra of polycrystalline samples of Zn₄O[(CH₃)₂CHCOO]₆ and Zn₄O[(CH₃)₃CCOO]₆, activated by Mn²⁺ ions at various concentrations, were investigated. An analytical theory was developed for the contour of the hyperfine components of the permitted and various types of forbidden transitions. On the basis of the obtained magnetic-resonance parameters conclusions were reached about the local symmetry and coordination of the Mn²⁺ ion in the investigated compounds.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 572–579, September–October, 1985.     

Organometallic complexes containing thiosemicarbazone and related ligands. Part II(1). η3-allyl dicarbonyl complexes of molybdenum(II) with attached thiosemicarbazone ligands

Summary The -allylmolybdenum(II) complexes [MoX(CO)₂-(NCMe)₂(³-C₃H₄R)] (X=Cl, Br and I; R=H and 2-Me) react either in dichloromethane or acetonitrile with thiosemicarbazones to give the new complexes [MoX-(CO)₂(RRCNNHCSNH₂)(³-C₃H₄R)] (R=H or Me; R'=Me, Et, Pr or Ph)via displacement of acetonitrile ligands.     

Potential function of internal rotation of (CH3)2CClNO,CH3CCl2NO,and their deuterium analogs

The potential function has been constructed for internal rotation of the NO-group in (CH₃)₂CClNO, CH₃CCl₂NO, and their deuterium analogs. It has been established that the N=O bond in the cis_Cl conformer of CH₃CCl₂NO does not eclipse the C-Cl bond, rather forming an angle of approximately 30. It has been shown that a change in substitutent on the -carbon atom may produce a substantial change in the form of the potential function of internal rotation (PFIR) of the NO group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 550–555, March, 1990.     

Synthesis,Crystal Structure,and Absorption Spectra of Neptunium(V) Di(acetamido) Nitrate (NpO2)(NO3)(CH3CONH2)2

The crystal structure of (NpO₂)(NO₃)(CH₃CONH₂)₂ was determined. The crystallographic data were are follows: a = 5.766(3) Å, b = 13.154(5) Å, c = 14.027(6) Å, V = 1064.0(8) ų, space group Pnma, Z = 4, _calcd = 2.804 g/cm³, R = 0.046, R _w = 0.102. The coordination polyhedron of Np is a pentagonal bipyramid whose equatorial positions are occupied by the oxygen atoms of the neighboring NpO₂ group, acetamide molecules, and of the nitrate ion. The IR and electronic absorption spectra of the compound were measured.     

Crystal structure of Li2Cu3(SeO3)2(SeO4)2

Summary Single crystal X-ray data of the hydrothermally grown new phase Li₂Cu₃(SeO₃)₂(SeO₄)₂ were measured with a four-circle diffractometer up to sin /=0.81 Å^–1 [I2/a,Z=4,V=1175.5 ų,a=16.293(6),b=5.007(2),c=14.448(6) Å, = 94.21(1)°]. The structure was determined by direct and Fourier methods and refined toR=0.034,R _w =0.027 for 2 086 independent reflections.Cu(1)^[4+1]O₅ forms a tetragonal pyramid, Cu(2)^{[4 + 2]}O₆ is a strongly elongated octahedron. The Li atom is surrounded by four O atoms forming a distorted tetrahedron. Se(IV)O₃ and Se(VI)O₄ groups are in accordance to literature, mean Se-O bond lengths are 1.714 and 1.644 Å.

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Die Kristallstruktur von Li₂Cu₃(SeO₃)₂(SeO₄)₂

Zusammenfassung Einkristall-Röntgendaten der hydrothermal gezüchteten neuen Phase Li₂Cu₃(SeO₃)₂(SeO₄)₂ wurden mit einem Vierkreisdiffraktometer im Bereich bis zu sin /=0.81 Å^–1 gemessen [I2/a,Z=4,V=1175.5 ų,a=16.293(6),b=5.007(2),c=14.448(6) Å, =94.21(1)°]. Die Kristallstruktur wurde mittels direkter und Fourier-Methoden bestimmt und für 2 086 unabhängige Reflexe zuR=0.034,R _w =0.027 verfeinert.Cu(1)^[4+1]O₅ bildet eine tetragonale Pyramide, Cu(2)^[4+2]O₆ ist ein stark verlängertes Oktaeder. Das Li-Atom ist von vier O-Atomen in Gestalt eines verzerrten Tetraeders umgeben. Die Se(IV)O₃-und Se(VI)O₄-Gruppen entsprechen der Literatur, die mittleren Se-O-Abstände betragen 1.714 und 1.644 Å.

     

Photochemical reactions of Re(CO)5Br with Ph2P(CH2) n PPh2 (n = 1, dppm; 2, dppe; 3, dppp)

The new complexes fac-[Re(CO)₃Br{Ph₂P(CH₂) _n PPh₂}] (1a–3a) [(1a), n = 1; (2a), n = 2; (3a), n = 3] and [Re₂(CO)₈Br₂{-Ph₂P(CH₂) _n PPh₂}] (1b–3b) [(1b), n = 1; (2b), n = 2; (3b), n = 3] have been prepared by the photochemical reaction of Re(CO)₅Br with Ph₂P(CH₂) _n PPh₂ (n = 1, dppm; 2, dppe; 3, dppp). The complexes have been characterized by elemental analysis, mass spectroscopy, f.t.-i.r. and ³¹P-[¹H]-n.m.r. spectrometry. The spectroscopic studies suggest cis-chelate bidentate coordination of the ligand in fac-[Re(CO)₃Br{Ph₂P(CH₂) _n PPh₂}] (1a–3a) and cis-bridging bidentate coordination of the ligand between two metals in [Re₂(CO)₈Br₂{cis--Ph₂P(CH₂) _n PPh₂}] (1a–3a).     

Beeinflussung der Umsetzung von Phosphor(V)-chlorid mit Isopropenylacetat durch polare Lösungsmittel

Zusammenfassung Bei der Umsetzung von PCl₅ mit Isopropenylacetat verlaufen zwei konkurrierende Reaktionen, deren Wechselbeziehung weitgehend vom Charakter des Lösungsmittels abhängt.In PCl₃- und CCl₄-Lösung^1–4 entsteht beim Erhitzen zunächst ein komplexes Anlagerungsprodukt,1 (R=R=CH₃), das durch Wanderung der Acetylgruppe in die -Stellung eine Umlagerung erfährt. Als Endprodukt (nach Behandlung des Reaktionsgemisches mit SO₂) bildet sich das Säurechlorid der -Acetyl--chlorpropenylphosphonsäure4 (3a:R=R=CH₃). Die Nebenreaktion ergibt nur unbedeutende Mengen von phosphorhaltigen niedrigsiedenden Verbindungen. In Phosphoroxychlorid- oder Thionylchloridlösung wird die Nebenreaktion, namentlich bei niederer Temperatur, zur Hauptreaktion. Das Gemisch enthält CH₃CCl₂CH₂POCl₂, CH₃CCl=CHPOCl₂ und CH₃COCH₂POCl₂, die als entsprechende Äthylester nachgewiesen wurden. In POCl₃ und SOCl₂ beim Erhitzen sowie in PCl₃ und CCl₄ bei niedriger Temp. treten beide konkurrierende Reaktionen nur mäßig in Erscheinung.

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Two competing reactions occur between PCl₅ and isopropenyl acetate; their ratio depends largely on the solvent. In PCl₃ and CCl₄ on heating a complex adduct1 (R=R=CH₃) ist first formed which undergoes rearrangement by migration of the acetyl group into the -position. The final product, after treatment of the reaction mixture with SO₂, is -acetyl--chloropropenyl phosphonic acid chloride (3a). The side reaction yields only insignificant amounts of phosphorus-containing low boiling compounds. In POCl₃ or SOCl₂ the side reaction becomes the main reaction especially at low temperatures. The mixture contains CH₃CCl₂CH₂POCl₂, CH₃CCl=CHPOCl₂ and CH₃COCH₂ POCl₂, identified as their ethyl esters. In POCl₃ and SOCl₂ on heating, and in PCl₃ and CCl₄ at low temperatures, the two competitive reactions take place only to a moderate extent.

     

Mössbauer spectroscopic and X-ray diffraction study of the thermal decomposition of Fe(CH3COO)2 and FeOH(CH3COO)2

Thermal decomposition of iron(II) acetate, Fe(CH₃COO)₂, and iron(III) acetate hydroxide, FeOH(CH₃COO)₂, has been studied using⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction. Samples were thermally treated in air atmosphere between 150°C and 1000°C. The formation of maghemite '-Fe₂O₃, and hematite, -Fe₂O₃, is discussed. Hematite appears as the final decomposition product.     

Binuclear Osmium μ-Oxocarboxylate Complexes [Os2(μ-O)(μ-O2CR)2Cl4L2] (R = CH3, CCl3; L = PPh3, AsPh3) and Their Electrochemical Behavior in Dichloromethane

Cyclic voltammetry and galvanostatic coulometry techniques were used to determine how the redox properties of osmium binuclear -oxocarboxylates [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PPh₃ and R = CH₃; L = AsPh₃) are influenced by the nature of the bridging carboxylate ligand RCOO^– and ligand L. It was shown that all compounds in solution of dichloromethane undergo two single-electron reduction processes. The data obtained were compared with the DFT calculations of the electronic structure of the model complexes [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PH₃ and R = CH₃; L = AsH₃).     

Radical ions : XXVIII. Tris(trimethylsilylmethyl)aminium,N(CH2Si(CH3)3)3: A stable fluxional aminium radical cation

The first ionization potentials of 11 silylmethyl-substituted amines R_3?nN(CH₂Si(CH₃)₃)_n as determined photoelectron spectroscopy range from 9.07 eV to 7.66 eV. The most easily ionized molecule, N(CH₂Si(CH₃)₃)₃, can also be oxidized with AlCl₃ in H₂CCl₂ solution to its aminium radical cation. The ESR spectra recorded between 180 K and 310 K display a strong temperature dependence due to rotations around the >NCH₂bonds.