The Kinetics of the Anation Reaction of Aquopentaamminerhodium(III) lon by Oxalate in Aqueous Acidic Solution

The anation reaction of aquopentaamminerhodium(III) by oxalate has been studied in the temperature range 51–69°C and acidity range 0 ≤ pH ≤ 4.5 for oxalate concentrations up to 0.25 M and at ionic strength 1.0 M. The kinetic results provide evidence for the formation of an ion-pair between the complex ion and HC₂O(Q₁) and C₂O₄^2?(Q₂), where Q₁ = 2.3 M^?1 and Q₂ = 8.1 M^?1 at 60°C, but no evidence for an ion-pair with H₂C₂O₄ exists. The values of the rate constants at 60°C for anation by H₂C₂O₄, HC₂O and C₂O₄^2? are k₀ = 1.5 · 10^?4 M^?1 sec^?1, k₁ = 1.4 · 10^?4 sec^?1 and k₂ = 1.2 · 10^?4 sec^?1. The corresponding values for ΔH≠ and ΔS≠ are reported and the results discussed with reference to analogous reactions of Rh(III) and Co(III).     

Hydroamination of alkynes with aromatic amines catalyzed by digallane (dpp-bian)Ga—Ga(dpp-bian)

Digallane (dpp-bian)Ga—Ga(dpp-bian) (1) (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) catalyzes the addition of 4-chloroaniline to some terminal alkynes RC≡CH (R = Buⁿ, Ph, 4-MeC₆H₄). The reaction orders in each of the substrates were found for the reaction of phenylacetylene with 4-chloroaniline catalyzed by compound 1. The reaction of compound 1 with phenylacetylene in a molar ratio of 1: 10 led to 1-[N-(2,6-diisopropylphenyl)imino]-2-(1-phenylethylidene)acenaphthene (5) and the compound [C₁₂H₆(NC₆H₃Pr₂ ⁱ)(PhC=CH₂)(PhC=CH)]Ga(C≡CPh)₂ (6). The reaction of digallane 1 with phenylacetylene and aniline in a stoichiometric ratio of 1: 2: 2 gave bis-anilide (dpp-bian)-Ga[N(H)Ph]₂ (7) in 40% yield. The compound (PhC≡C)₃Ga·THF (9) was obtained by the reaction of three equivalents of sodium phenylacetylide (prepared in situ from phenylacetylene and sodium) with one equivalent of GaCl₃ in tetrahydrofuran. Compounds 5—7 and 9 were characterized by IR spectroscopy, ¹H NMR spectroscopy was used to characterize products 5, 6, and 9, whereas EPR spectroscopy was used for amide 7. The structures of compounds 5—7 and 9 were determined by single crystal X-ray diffraction analysis.     

Reaction Kinetics of Carbon Dioxide (CO2) Absorption in Sodium Salts of Taurine and Proline Using a Stopped‐Flow Technique

The pseudo–first‐order reaction rate constants (k₀, s^?1) for the reaction of carbon dioxide in aqueous solutions of sodium taurate (NaTau) and sodium prolinate (NaPr) were measured using a stopped‐flow technique at a temperature range of 298–313 K. The solutions concentration varied from 5 to 50 mol m^?3 and from 4 to 12 mol m^?3 for NaTau and NaPr, respectively. Comparing the k₀ values, aqueous NaPr was found to react very fast with CO₂ as compared with the industrial standard aqueous monoethanolamine (MEA) and aqueous sodium taurate (NaTau) was found to react slower than aqueous MEA at the concentration range considered in this work. For the studied amino acid salts, the order of the reactions was found to be unity with respect to the amino acid salt concentration. Proposed reaction mechanisms such as termolecular and zwitterion reaction mechanisms for the reaction of CO₂ with aqueous solutions were used for calculating the second‐order reaction rate constants (k₂, m³ mol^?1 s^?1). The formation of zwitterion during the reaction with CO₂ was found to be the rate‐determining step, and the deprotonation of zwitterion was instantaneous compared to the reverse reaction of zwitterion to form an amino acid salt. The contribution of water was established to be significant for the deprotonation of zwitterion. Comparing the pseudo–first‐order reaction rate constants (k₀, s^?1) of various amino acid salts with CO₂, NaPr was found to be the faster reacting amino acid salt. The activation energy for NaTau was found to be 48.1 kJ mol^?1 and that of the NaPr was found to be 12 kJ mol^?1. The Arrhenius expressions for the reaction between CO₂ and the studied amino acid salts are      

Synthesis of a cyclic dinuclear organotin carboxylate via simultaneous debenzylation and decarbonylation reactions: X-ray crystal structure of [(PhCH2)2{O2CC6H4{N(H)N(C6H3-4(O)-5-O)}-o}Sn]2

The complex, [(PhCH₂)₂{O₂CC₆H₄{N(H)N(C₆H₃-4(O)-5-O)}-o}Sn]₂ (1), is obtained as the exclusive reaction product from the reaction of sodium 2-[(E)-2-(3-formyl-4-hydroxyphenyl)-1-diazenyl]benzoate and (PhCH₂)₃SnCl. The reaction possibly proceeds via Dakin type rearrangements where arylazosalicylaldehyde is oxidized to arylazocatechol, followed by facile Sn-C bond cleavage. Complete assignments were achieved by ¹H, ¹³C, 2D ¹H-¹¹⁹Sn HMQC (¹¹⁹Sn chemical shift), 1D gs ¹H-¹⁵N HMQC (¹J(¹⁵N, ¹H) coupling constant) NMR and ESI-MS. The crystal structure of compound 1 as determined by X-ray diffraction analyses shows a cyclic centrosymmetric dinuclear moiety linked into extended chains by pairs of long Sn?O contacts of approximately 3.2 Å. Two polymorphs were identified and their structures differ primarily in the packing arrangement afforded by the benzyl groups. In one polymorph, when viewed along the Sn?Sn vector, the benzyl groups at each Sn-atom are oriented to form an S-shape, while they form a U-shape in the second polymorph.     

NMR spectra of a hydrocarbon-soluble organosodium compound and its lithium analogs

¹H,²³Na, and⁷Li NMR spectra of 2-ethyl hexylsodiurn, 2-ethylhexyllithium, and isobutyllithium obtained in the reaction of the corresponding alkyl chlorides and metals have been recorded. The¹H N MR signal for the protons of the CH₂Na group is shifted upheld compared with that for the protons of the CH₂Li group (doublets at -0.88 and -0.83, respectively). The composition of the products of reaction of 2-ethylhexyl chloride with sodium depends on the form of the metal reagent employed. The use of sodium balls with diameter up to 2 mm results in the formation of products containing ionic chlorine (30–50 % with respect to Na); the reaction with the dispersion proceeds faster and the reaction product is chlorine-free. The²³Na NMR spectra of these substances are also different, which is explained by the formation of 2-ethylhexylsodium complexes with NaCl in the former case.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 883–885, April, 1996.     

Studies on the interaction of peroxy radicals with transition metals complexes: I. Effect of 2-cyano-2-propyl and 2-cyano-2-propyl peroxy radicals on cobaloximes

Reactions of CH₃Co(DH)₂py (1) and [Co(DH)₂py]₂ (2) with (CH₃)₂(CN)C (r) and (CH₃)₂(CN)COO (rO₂) radicals were investigated. At 60°C, reaction or r with (1) results in non-homogeneous ligand decomposition, whereas for 2, complex (CH₃)₂CNCCo(DH)₂py (6) and a precipitate are formed. Ligand decomposition also took place at 60°C when the reaction of rO₂ radicals with 1 and 2 was investigated. However, the same reaction with rO₂ radicals at −10°C, yielded two complexes, CH₃OOCo(DH)₂py (3) and Co(DH)₂py (4) with 1, and complex 6 for the reaction of rO₂ with 2.     

Palladium(II)-allyl complexes containing chiral N-donor ferrocenyl ligands

A study of the reactivity of enantiopure ferrocenylimine (S_C)-[FcCHN-CH(Me)(Ph)] {Fc =  (η⁵-C₅H₅)Fe{(η⁵-C₅H₄)-} (1a) with palladium(II)-allyl complexes [Pd(η³-1R¹,3R²-C₃H₃)(μ-Cl)]₂ {R¹ = H and R² = H (2), Ph (3) or R¹ = R² = Ph (4)} is reported. Treatment of 1a with 2 or 3 {in a molar ratio Pd(II):1a = 1} in CH₂Cl₂ at 298 K produced [Pd(η³-3R²-C₃H₄){FcCHN-CH(Me)(Ph)}Cl] {R² = H (5a) or Ph (6a)}. When the reaction was carried out under identical experimental conditions using complex 4 as starting material no evidence for the formation of [Pd(η³-1,3-Ph₂-C₃H₃){FcCHN-CH(Me)(Ph)}Cl] (7a) was found. Additional studies on the reactivity of (S_C)-[FcCHN-CH(R³)(CH₂OH)] {R³ = Me (1b) or CHMe₂ (1c)} with complex 4 showed the importance of the bulk of the substituents on the palladium(II) allyl-complex (2-4) or on the ferrocenylimines (1) in this type of reaction. The crystal structure of 5a showed that: (a) the ferrocenylimine adopts an anti-(E) conformation and behaves as an N-donor ligand, (b) the chloride is in acis-arrangement to the nitrogen and (c) the allyl group binds to the palladium(II) in a η³-fashion. Solution NMR studies of 5a and 6a and [Pd(η³-1,3-Ph₂-C₃H₃){FcCHN-CH(Me)(CH₂OH)}Cl] (7b) revealed the coexistence of several isomers in solution. The stoichiometric reaction between 6a and sodium diethyl 2-methylmalonate reveals that the formation of the achiral linear trans-(E) isomer of Ph-CHCH-CH₂Nu (8) was preferred over the branched derivative (9). A comparative study of the potential utility of ligand 1a, complex 5a and the amine (S_C)-H₂N-CH(Me)(Ph) (11) as catalysts in the allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with the nucleophile diethyl 2-methylmalonate (Nu⁻) is reported.     

The Raman spectra of serine and 3,3-dideutero-serine in aqueous solution

The Raman spectra of serine [α-amino-β-hydroxypropionic acid; HOCH₂CH(NH₃)⁺COO⁻] and 3,3-dideutero-serine [HOCD₂CH(NH₃)⁺COO⁻] in aqueous solution were studied in the range 4000–300 cm⁻¹. The data obtained for the deuterated compound are novel and provide compelling evidence that previously reported assignments for the undeuterated amino acid should be revised.     

Kinetics of the reaction of poly(α-methylstyryl sodium,potassium, and cesium) with t-butyl chloride in tetrahydrofuran

The kinetics of the reaction of “living” poly(α-methylstyrl sodium, potassium, and cesium) with t-butyl chloride have been studied spectrophotometrically in tetrahydrofuran (THF) in the temperature range 283–303 K. The reactions, when the free ions present in solution are suppressed by tetraphenylboron salt, are first order with respect to both living ends and halide concentrations. Additions of tetraphenylboron salts produce a slight retardation effect on the rate of reaction in the case of sodium, indicating only a small contribution of free ions to the overall rate; in the case of potassium, there is no apparent effect. Analysis of the data indicates that the free ion is approximately 30 times more reactive than the sodium ion pair. The Arrhenius plots for contact ion-pair termination are linear and the activation energies and preexponential factors determined are E = 38.6 kJ mole^?1, log A = 4.44 liter mole^?1 sec^?1 and E = 46.0 kJ mole^?1, log A = 5.10 liter mole^?1 sec^?1. The reaction mechanism is interpreted in terms of elimination plus some side reaction to produce two unexpected reaction products—isobutane and a 315–320-nm absorbing grouping in the polymer.     

Exploring the activities of vanadium,niobium, and tantalum PNP pincer complexes in the hydrogenation of phenyl-substituted CN,CN, CC,CC, and CO functional groups

The structures and stability of the designed PNP pincer amido M(NO)₂(PNP) and amino ^HM(NO)₂(PN^HP) complexes [M = V, Nb, and Ta, PNP = N(CH₂CH₂P(isopropyl)₂)₂, PN^HP = HN(CH₂CH₂P(isopropyl)₂)₂] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H₂ environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-CN, Ph-CHNH, Ph-CHNH-Ph, Ph-CHNCH₂Ph, Ph-CCH, Ph-CHCH₂, Ph-CHO, and Ph-COCH₃, the reaction prefers either a two-step or one-step mechanism for the hydridic MH and protonic NH transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges.     

A combined experimental and model analysis on the effect of pH and O2(aq) on γ-radiolytically produced H2 and H2O2

The effects of pH and dissolved O₂ on the γ-radiolysis of water were studied at an absorbed dose rate of 2.5 Gy s⁻¹. Argon- or air-saturated water with no headspace was irradiated and the aqueous samples were analyzed for molecular radiolysis products (H₂ and H₂O₂) as a function of irradiation time. The experimental results were compared with computer simulation results using a comprehensive water-radiolysis kinetic model, consisting of the primary radiolysis production, subsequent reactions and related acid–base equilibria. Both the experimental and computer model results were discussed based on the steady-state kinetic analysis of smaller reaction sets consisting of key production and removal reactions. While the main production path for a water decomposition product is the primary radiolysis, the main removal path varies. For H₂O₂ the main removal path is the reactions with e_aq⁻ and OH, whereas for H₂ it is the reaction with OH. As a result, the presence of a dissolved species, or a change in chemical environment, affects the concentrations of H₂O₂ and H₂ through interaction with radicals e_aq⁻ and OH. Over a wide range of conditions, there exist quantitative but simple relationships between the radical and the molecular product concentrations. The experimental and model analyses show that dissolved oxygen increases the steady-state concentrations of H₂O₂ and H₂ by reacting with OH and e_aq^–, and the impact of oxygen is more noticeable at pH below 8. The steady-state concentrations of water decomposition products are nearly independent of pH in the range 5–8. However, raising pH above the pKa value of the acid–base equilibrium of H (⇆e_aq⁻+H⁺) significantly increases [H₂O₂] and [H₂] at the expenses of [OH] and [e_aq^–]. At pH >10, the radiolytical production of O₂ becomes significant, but at a finite rate. This considerably increases the time for the irradiated system to reach a steady state, and is responsible for different impacts on [H₂O₂] and [H₂] due to radically produced O₂, compared to impacts due to initially dissolved O₂. Model sensitivity analysis has shown that at higher pHs (pH >10) transient species such as O₂⁻ and O₃⁻ play a major role in determining the steady-state concentration of molecular products H₂ and H₂O₂. Further validation of the water radiolysis model, particularly at higher pHs, is also discussed.     

Kinetics and mechanism of the homogeneous reaction between some manganese(III)-Schiff base complexes and hydrogen peroxide in aqueous and sodium dodecyl sulphate solutions

Summary The kinetics of the reaction between H₂O₂ and some Schiff base complexes of Mn^III have been investigated in both aqueous and micellar sodium dodecyl sulphate (SDS) solution. The reaction rate is first order in both H₂O₂ and [complex], and inversely proportional to [H⁺]. The second-order rate constant increases in the sequence [Mn(salophen)(OAc)] > [Mn(salen)(OH₂)]-ClO₄ > [Mn(salen)(OAc)]H₂O, where salen = N,N-bis-(salicylidene)ethylenediamine and salophen = N,N-bis-(salicylidene)-o-phenylenediamine. At SDS concentrations below the critical micellar concentration, there is almost no effect on the rate of reaction whereas at higher concentrations the reaction rate increases slightly. A mechanism involving Mn^II and a peroxo intermediate is proposed.     

The dynamics of reactions of O(3P) atoms with allene and methylacetylene

The reactions of O(³P) atoms with allene and methylacetylene: O+CH₂=C=CH₂

CO+C₂H₄,ΔH₁⁰ = ?119.4 kcal/mole, O+CH₃-C

CH

CO+C₂H₄,ΔH₂⁰ = ?117.8 kcal/mole were studied at 293 K with a CO laser resonant absorption and a discharge-flow GC-sampling method. The CO formed in reaction (1) was found to have a vibrational temperature of 5100 ± 100 K, compared with 2400 ± 200 K in (2). The good agreement between the observed CO vibrational distributions and those predicted by simple statistical models indicates that the reaction energies were completely randomized.The present results also showed unambiguously that CH₃CH, instead of C₂H₄, was produced initially in reaction (2).     

Product formation in the association reaction of ClO with NO2 investigated by diode laser kinetic spectroscopy

Diode laser spectroscopy has been employed to monitor the formation of chlorine nitrate (ClONO₂) in the association reaction of ClO with NO₂. Chlorine nitrate is the only stable end-product of this reaction at room temperature. Time-resolved measurements of ClONO₂ formation using molecular modulation showed no evidence for any involvement of unstable isomers of ClNO₃ in the reaction. These measurements gave a value of k₁ = (1.8 ± 0.4) × 10^?31 cm⁶/molecule² · s for the reaction at 295 K and an upper limit of 5 ms for the lifetime of any isomeric products at this temperature.     

Titanium(IV) phosphinoamide as a unique bidentate ligand for late transition metals II: TiRu heterobimetallics bearing a bridging chlorine atom

Treatment of a titanium phosphinoamide, (Ph₂PN^tBu)₂TiCl₂ (1), with [Cp^∗RuCl]₄ in THF at room temperature afforded a TiRu heterobimetallic complex, of which crystallographic study showed the molecular structure to be a six-membered dimetallacyclohexane, Cp^∗Ru(μ-Cl)(Ph₂PN^tBu)₂TiO (3). A boat conformation of the dimetallacycle leads to effective linking of the two metal centers by two phosphinoamide ligands, and bridging of a chlorine atom over the TiRu axis. The TiRu heterobimetallics were synthesized by the reaction of 1 with Cp^∗Ru(COD)Cl or Cp^∗Ru(TMEDA)Cl, whereas no reaction occurred between 1 and Cp^∗Ru(PCy₃)Cl. A primary product of this reaction would be a trichloride, Cp^∗Ru(μ-Cl)(Ph₂PN^tBu)₂TiCl₂ (2). In fact, careful treatment of 1 with [Cp^∗RuCl]₄ afforded 2 as the main product which was detected by NMR and ESI-MS spectra; 2 was converted to 3 in contact with 1 equivalent of water.     

The N(4S) + N2O(X̃1∑) reaction

The title reaction, which is spin‐forbidden for N₂(X¹∑) + NO(X²Π) production, has been studied from 960 to 1130 K in a high‐temperature photochemistry reactor. No reaction could be observed, indicating k < 1 × 10^?15 cm³ molecule^?1 s^?1. It is concluded that there is no significant contribution from the spin‐allowed exothermic path leading to N₂(X¹∑) + NO(a⁴Π). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 387–389, 2001     

Kinetic Salt Effect in the 18O-Exchange Reaction between Bromate and Water

The kinetic salt effect in the ¹⁸O-exchange reaction between bromate ion and water has been investigated at 60° in a range of ionic strength from 0.02M < I < 1.9M using NaNO₃ or NaClO₄ as inert salts. From the experimental data the following relation was deduced for the uncatalysed reaction path In the H⁺-catalysed reaction path the Brønsted-Davies equation was obeyed up to I ? 0.1M At I > 0.8M the sign of Δ logk₂/Δ I^1/2 was positive. The theoretical interpretation of these results is consistent with the mechanistic evidence obtained previously from the rate law and the solvent isotope effects.     

Zur Struktur von zwei Hydraten des Natriumphenolats: C6H5ONa · H2O und C6H5ONa · 3 H2O

The Structures of two Hydrates of Sodium Phenoxide: C₆H₅ONa · H₂O and C₆H₅ONa · 3 H₂O In the monohydrate of sodium phenoxide sodium is coordinated by 4 oxygen atoms having an average distance Na? O of about 2.631 Å being arranged in form of a distorted tetrahedron. The oxygen atoms of water and phenoxid serve as bridging ligands. Hence, the structure can be considered as a network with a general formula [Na^[4]O]. Moreover, the oxygen atoms are linked via hydrogen bonding. In the trihydrate of sodium phenoxide sodium is surrounded with 5 oxygen atoms with an average distance of 2.39 Å forming a tetragonal pyramide. The oxygen of the phenoxide, however, does not participate in the coordination of the sodium ion. The coordination polyhedrons are connected by sharing edges and verteces. The resulting layer can be described by the general formula [Na^[5]O₂^[2]O^[2]O^[1]]. Via hydrogen bonding the phenoxide ions are attached to this layer.     

Kinetics and mechanism of oxidation of formic acid by bismuth(V) in aqueous phosphoric acid medium

The solution of bismuth(V) was prepared by digesting sodium bismuthate in aqueous phosphoric acid (3.0 mol dm⁻³), the resulting pink colour solution absorbs in the visible region at 530 nm (640 dm³ mol⁻¹ cm⁻¹). The stoichiometry of the oxidation of formic acid by bismuth(V) corresponds to the reaction as represented by the Eq. ( 1 ). (1) The observed kinetic rate law is given by the Eq. ( 2 ); (2) where Bi^V and [HCO₂H] are the gross analytical concentrations of bismuth(V) and formic acid respectively. A plausible reaction mechanism corresponding to the rate law (2) has been proposed. Also the pattern of reactivity of bismuth(V) in HCIOHF mixture and H₃PO₄ respectively has been compared. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 491–497, 2000