Theoretical studies of the reactions of O(~3p) with halogenated methyl (Ⅰ)——Reaction mechanism of the O(~3p) CH_2Cl reaction

The reaction of O(~3P) with CH_2Cl radical has been studied using ab initio molecular orbital theory. G2 (MP2) method is used to calculate the geometrical parameters, vibrational frequencies and energies of various stationary points on the potential energy surface. The reaction mechanism is revealed. The addition of O(~3P) with CH_2Cl leads to the formation of an energy rich intermediate OCH_2Cl which can subsequently undergo decomposition or isomerization to the final products. The calculated heat of reaction for each channel is in agreement with the experimental value. The production of H CHClO and Cl CH_2O are predicted to be the major channels. The overall rate constants are calculated using transition state theory on the basis of ab initio data. The rate constant is pressure independent and exhibits negative temperature dependence at lower temperatures, in accordance with the experimental results.     

Polymeric (NO)3(N2O) n , (NO)3(N2O) n + , and (NO)3(N2O) n − : an interpretation of experimental observations

Semi-empirical and ab initio calculations are reported which provide a possible explanation for reported experimental results on 2-photon ionization of NO containing a few percent of N₂O, which found (NO)₃(N₂O) _n ^+or? clusters to be significantly more abundant than other (NO) _m (N₂O) _n products. It is found that the observed abundances of (NO)₃(N₂O) _n ionic clusters may be accounted for by the existence of covalent cyclic trimers of nitric oxide attached to oligomers of nitrous oxide. The extra stability of NO trimers in the observed clusters appears to arise from (NO) ₃ ⁺ rather than (NO)₃. Attachment of an (N₂O) _n side chain to (NO) ₃ ⁺ occurs exothermically. It is suggested that the addition of N₂O to cyclic-(NO) ₃ ⁺ might provide a means of making a polymer of nitrous oxide, which could have useful properties.     

Theoretical study of the energetics of the O3(X̃ 1A1) → O2(X 3Σ−g) + O(3P) dissociation process

The dissociation energy (D_e) for the O₃(X̃ ¹A₁) → O₂(X ³Σ⁻_g) + O(³P) process is computed using MC SCF, CI, MBPT, and CCD methods. A full-valence MC SCF calculation utilizing a [9s5p3d1f/5s3p2d1f] basis set yields a D_e value of 0.43 eV, far below the experimental value of 1.13 eV, demonstrating the importance of correlation effects involving non-valence orbitals. A CI calculation in the same basis set allowing for all single and double excitations from three-reference configuration yields a D_e value of 0.72 eV. This value is increased to 1.06 eV when the Davidson correction is included. When the number of reference configurations is increased to eight, the resulting CI calculation gives a D_e value of 0.82 eV prior to the Davidson correction and 1.10 eV after this correction.     

Kinetic studies on the reactions of Ru(II) tetraammines with CS2N−3

The kinetics of the reactions of Ru(II) complexes with CS₂N⁻₃ ions were studied spectrophotometrically. The formation rate constants data for trans-[Ru(NH₃)₄L(CS₂N₃)] are 2.2 × 10², 1.8 × 10 and 1.3 × 10² M⁻¹ s⁻¹ for L = SO^2-₃, HSO⁻₃ and P(OEt)₃), respectively [μ = 1.0 M (NaCF₃COO), 25°C]. Under the same experimental conditions, the values of k⁻¹ (specific rate for the aquation reaction) are 1.5 × 10⁻², 5.0 × 10⁻² and 4.5 × 10 s⁻¹ for L = SO²⁻₃, HSO⁻₃ and P(OEt)₃, respectively. The free-energy change (ΔG^≠) for the systems where L = P(OEt)₃ and SO²⁻₃ are in agreement within the experimental error. It was observed that the affinity of the CS₂N⁻₃ ion decreases with the increasing π-acidity of the auxiliary ligand L. The order of affinity of the CS₂N⁻₃ ion for the Ru(II) center studies is SO²⁻₃ > HSO⁻₃ > P(OEt)₃ >SO₂.     

Ligand field analysis of tris(aminoacidato)cobalt(III) complexes with glycinato(N,O) and β-alaninato(N,O) metal chelate rings

In addition to showing a well-known demarcation between facial and meridional configurations the ligand field spectra of Co(βAla)_x(Gly)_3-x (x = 1 or 2) [βAla = β-alan- inato(N,O) ring, and gly = glycinato(N,O) ring] complexes provide a rare example of a marked difference in the observed splitting pattern of the¹T_1g(O_h) level among the three possible meridional isomers generated by cyclic permutation of chelate rings with respect to the pseudo three-fold axis. Angular overlap calculations which consider an anisotropy of the metal-car☐ylate oxygen donor interaction reproduce fairly well the ligand field spectra of the complete series of Co(βAla)_x(Gly)_3-x (x = 0, 1, 2 or 3) complexes.     

Stability constants of the complexes of Zn(II) and Mn(II) with N,N′-bis(2-hydroxyethyl) aminomethyl

The acid dissociation constants of N,N′-bis(2-hydroxyethyl) aminomethyl phosphonic acid (BHAMP) and the stability constants with Zn⁺⁺ and Mn⁺⁺ were determined at 25°C and at an ionic strength of 0.10 by means of potentiometric methods. The existence of a stable chelate species YM is illustrated. The equilibrium constants reported were calculated by the method developped by Schwartzenbach.     

How active is the bend excitation of methane in the reaction with O(3P)?

The role of bending excitation of methane in the reaction with O(3P) is investigated in a crossed-beam experiment. Previous theories predicted that either stretch or bend excitation of the reactant promotes chemical reactivity and that initial bending excitation of CH4 preferentially yields umbrella-excited CH3 products. Experimentally, both predictions for bend-excited reagent were not borne out in this investigation. We found instead that compared to the ground-state reagent, bend-excited methane yields more vibrational excitation of the hydroxyl coproduct. The first reported product angular distributions show predominant backward scatterings for both ground-state and bend-excited methanes, which corroborate well with a direct rebound reaction mechanism.     

The Reaction of Ketenylidenetriphenylphosphorane (Ph3P˭C˭C˭O) with Acidic H‒E (E˭O,N) Bonds

Abstract

The reactivity of ketenylidenetriphenylphosphorane (1) with the protic reagents 2,4,6-trimethylphenol (7), 2,6-di-tert-butyl-4-methylphenol (8), and diphenylamine (9) has been explored. Three novel carbonyl-stabilized ylides have been synthesized and characterized. Crystal structures were obtained for Ph₃PCHC(O)O(C₆H₂Me₃) (11), Ph₃PCHC(O)O(C₆H₂t-Bu₂Me) (12), and Ph₃PCHC(O)NPh₂ (13), respectively. These products were then methylated in an attempt to develop a new route to low-valent carbon compounds. Crystals of [Ph₃PCH(CH₃)C(O)O(C₆H₂Me₃)]I (14) were isolated and characterized but this route did not prove to be synthetically useful, at least toward the goal of preparing low-valent carbon-centered materials. Finally, 1 was also reacted with the bulky tin reagent, bis[bis(trimethylsilyl)amido]tin(II), in the presence of 2,4,6-trimethylphenol. A complex mixture of products was obtained, from which crystals of an unusual chelated tin compound (15) were isolated and characterized using X-ray crystallography.     

Crystal Structure of the Addition Compound of N,N′-Bi(2-pyridylmethyl)-Oxamide and the Complex of Copper with 1,10-Phenanthroline

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Spectrophotometric Method for the Determination of Cobalt with N,N′-Bis(2-Aminobenzoyl)Ethylenediamine

 A simple and direct spectrophotometric method has been developed for the determination of cobalt(II) using N,N′-Bis(2-aminobenzoyl)ethylenediamine (Baben). The method is based on the colour reaction between Baben and cobalt(II) in borax buffer (pH 9.2). The studies are carried out at 470 nm at which the calculated value of molar absorptivity is found to be 1.102 × 10⁴ L mol⁻¹ cm⁻¹. The system obeys Beer’s law over a wide range of concentration (2–20 μg/ml). The effect of interfering ions has been studied and the method was applied to the determination of cobalt in water, industrial effluents and in alloys and the results were highly satisfactory. Received May 8, 2000. Revision January 30, 2001.     

Coupling of ν(NH⋯N) vibrations with the γ(NH⋯N) overtone in solid imidazole derivatives

The IR spectra of a number of imidazole derivatives were studied in the solid state at room and liquid nitrogen temperatures. The bands ascribed to stretching and out-of-plane deformation vibrations of NH groups involved in strong NH⋯N hydrogen bonds were analysed. The energy of this bond reflected in the position of the ν(NH⋯N) band changes over a broad range so that it was possible to investigate band shaping due to the overlap with the overtone band of the γ(NH⋯N) mode. The correlation between the γ(NH⋯N) and ν(NH⋯) frequencies shows that the γ(NH⋯N) value for strong NH⋯N bridges only slightly depends on ν(NH⋯N).     

Structural characterization of the trans-equatorial isomer of (aqua)(ethylenediamine-N,N,N′-tripropionato)chromium(III) trihydrate,[Cr(edtrp)(H2O)] · 3H2O

The structure of trans-equatorial [Cr(edtrp)(H₂O)] · 3H₂O (edtrp^3– is the anion of ethylenediamine-N,N,N-tripropionic acid) was determined by single crystal X-ray diffraction. The chromium(III) ion is surrounded octahedrally by the two nitrogen and three oxygen atoms of the quinquedentate edtrp^3–, forming a five-membered diamine ring and the three six-membered -propionato chelate rings. The remaining coordination position is occupied by the H₂O ligand. The crystal structure conformation is compared to the result of recent molecular mechanics analysis. The ring strain of R and G chelate rings was found to be in agreement with the previously proposed mechanisms for the C—N bond cleavage and recombination.     

The Reaction of the Bis-spirocyclic Phosphazene [N 3 P 3 (O 2 C 12 H 8 ) 2 Cl 2 ] (O 2 C 12 H 8 = 2,2′-Dioxybiphenyl) with Thiophenols,in the Presence of Alkali Carbonates

The reactions of the spirocyclic phosphazene [N 3 P 3 (O 2 C 12 H 8 ) 2 Cl 2 ] (O 2 C 12 H 8 = 2,2'-dioxybiphenyl) with the thiophenols HS--C 6 H 4 --R and M 2 CO 3 (M = K or Cs) in refluxing acetone gave respectively the spirocyclic substituted derivatives [N 3 P 3 (O 2 C 12 H 8 ) 2 (SC 6 H 4 --R) 2 ] R = H ( 2a ), Br ( 2b ), OMe ( 2c ), NO 2 ( 2d ). The reaction is a two-step process the second of which is much faster than the first and the monosubstituted intermediate [N 3 P 3 (O 2 C 12 H 8 ) 2 (SC 6 H 4 --R)Cl] cannot be detected. By contrast, in the analogous reactions with the phenols HO--C 6 H 4 --R and M 2 CO 3 (M = K or Cs) in acetone or THF, to give the known derivatives [N 3 P 3 (O 2 C 12 H 8 ) 2 (OC 6 H 4 --R) 2 ], the first step is faster although both are very dependent on R, M and the solvent. Thus, in the case of the phenol HO--C 6 H 4 --OMe the reaction conditions could be adjusted to give the useful synthetic intermediate monosubstituted derivative [N 3 P 3 (O 2 C 12 H 8 ) 2 (OC 6 H 4 --OMe)Cl] ( 3 ). The reaction of [N 3 P 3 (O 2 C 12 H 8 ) 2 Cl 2 ] with the bifunctional reagent mercaptophenol HS--C 6 H 4 --OH was not specific and led to mixtures of cyclic and oligomeric products.     

The properties of the new Mn(II)–Co(II)–Mn(II)-type hetero-trinuclear oxime metal complexes with N4 and N4O2 ligands

1,3- and 1,2-calix[4]crown-7 and calix[4]crown-9 cone conformers were synthesized in acceptable yields by sequential introduction of two distal or proximal polyethylene glycolic chains with terminal hydroxyls at the lower rim, monotosylation, and intramolecular ring closure reaction. According to the two-phase extraction experiment, the title compounds showed mediocre affinity for alkali and alkaline earth metal picrates. The 1,2-calix[4]crown-9 extracted Sr²⁺ selectively among other alkaline earth metal cations.     

Reaction of N≡W(O(t)Bu)3 with σ3λ5-phosphoranes. The [2 + 2] cycloaddition across the W≡N triple bond results in the first representative of an inorganic four-membered metallacycle with conjugated endo- and exocyclic double bonds

The reactions of N≡W(O(t)Bu)(3) with the low-coordinate phosphorus compounds (Me(3)Si)(2)NP(NSiMe(3))(2) (I) and (Me(3)Si)(2)NPS(N(t)Bu) (II) were studied. Quantum chemical calculations were used to determine why Mo- and W-containing compounds with the same composition have different molecular structures.     

Critical phenomena in the topochemical reaction of water vapor with solid N,N′-ethylenebis (acetylacetoniminato)copper (II)

The effects of water vapor and temperature on the phase transition between anhydrous N,N-ethylenebis(acetylacetoniminato) copper (II) and the monohydrate have been studied by a piezoelectric microbalance method. The presence of a branch point and critical deceleration of the phase transition dynamics near that point have been observed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 2, pp. 149–153, March–April, 1993.This work was supported by a fundamental research grant from the State Committee on Science and Technology, Ukraine Council of Ministers.     

Theoretical Investigation for the Abstraction Reaction of H with (CH_3)_3GeH

The reaction of H atom with (CH3)3GeH is considered to play important role in chemical vapor deposition (CVD) processes used in the semiconductor industry 1-2. The reaction mechanism and kinetics nature for this reaction are therefore essential input data for computer-modelling studies directed towards obtaining an understanding of the factors controlling CVD processes. However, despite its importance, the kinetics work about this reaction was very limited. Only two groups studied exper…     

Chlorine reaction with platinum triamine [Pt(N,N-DimeTm)PyCl3]Cl (N,N-DimeTm = (CH3)2N(CH2)3NH2). Crystal structure of [Pt(N,N-DimeTm)Cl2], [Pt(N,N-DimeTm(Py)Cl3]Cl · H2O and [Pt{(CH3)2N(CH2)2C(O)NH}(Py)Cl3]

Treatment of platinum(II) diamine [Pt(N,N-DimeTm)Cl₂] (I) with pyridine gave tetramine [Pt(N,N-DimeTm)Py₂]Cl₂ (II); by oxidation with chlorine this was converted to Pt(IV) triamine, [Pt“(N,N-DimeTm(Py)Cl₃]Cl (III) with a six-membered chelate ring. According to X-ray diffraction data, the reaction of complex II with chlorine is accompanied by removal of the pyridine molecule from the trans-position to the NH₂ group of N,N-dimethyltrimethylenediamine. The reaction of complex III with chlorine at 20°C afforded a mixture of compounds (IV) and the complex [Pt“(CH₃)₂N(CH₂)₂C(O)NH”(Py)Cl₃] (V) with an amidate six-membered metal ring, dimethylpropioamide, which was also isolated upon refluxing a mixture of IV in an aqueous solution. The UV/Vis and IR spectra of the obtained complexes were studied, and X-ray diffraction analysis of I, III, and V was performed. The crystals of I are triclinic, space group P $ \bar 1 $ ; a = 7.6526(4) Å, b = 11.5571(6) Å, c = 12.4432(7) Å, α = 113.85(1)°, β = 96.54(2)°, γ = 106.78(2)°; Z = 4; R _hkl = 0.051. The crystals of III are monoclinic, space group C2/c; a = 36.715(2) Å, b = 7.8179(4) Å, c = 29.721(16) Å, β = 127.80(1)°; Z = 16; R _hkl = 0.036. The crystals of V are monoclinic, space group P2₁/n; a = 7.0398(6) Å, b = 27.458(2) Å, c = 7.687(6) Å, β = 106.270(1)°; Z = 4; R _hkl = 0.052.     

Ab initio study of the HCO 3 − /H2O exchange in the (NH3)3 ZnII(HCO 3 − ) complex

Summary The displacement of bicarbonate anion in the (NH₃)₃Zn^II(HCO ₃ ^– ) complex with water has been studied throughab initio calculations. It has been found that H₂O binds to the (NH₃)₃Zn^II(HCO ₃ ^– ) species yielding a stable pentacoordinate (NH₃)₃Zn^II(HCO ₃ ^– )(H₂O) complex. The results also indicate that deprotonation of water in the pentacoordinate species facilitates the release of HCO ₃ ^– , although, the presence of HCO ₃ ^– in the coordination sphere of Zn^II makes such deprotonation more difficult. Environmental effects have been considered in the study of HCO ₃ ^– /H₂O exchange.A contribution from the Grup de Química Quàntica de l'Institut d'Estudis Catalans     

Thermodynamics of the Extraction of U(VI) by N,N′-Didecanoylpiperazine

A novel extractant, N, N-didecanoylpiperazine (DDPEZ), was synthesized for the first time. The extraction of U(VI) by DDPEZ from aqueous nitric acid media in carbon tetrachloride has been studied. The dependence of extraction distribution ratio on concentration of aqueous nitric acid, extractant, salting-out agent and temperature was investigated and the enthalpy of the extraction was calculated.