Kinetics and mechanism of oxidation of thiosulphate by the complex ion [MnIV3(μ-O)4(phen)4(H2O)2]4+ (phen = 1,10-phenanthroline) in weakly acidic aqueous media

The trinuclear complex ion [Mn^IV ₃(-O)₄(phen)₄(H₂O)₂]⁴⁺ (1) is quantitatively reduced by an excess of S₂O₃ ^2– to Mn^II, but the binuclear complex [Mn^IIIMn^IV(-O)₂(phen)₄]³⁺, (2) is the only manganese product when [S₂O₃ ^2–] = 1.5 [(1)]. With an excess of S₂O₃ ^2– biphasic kinetics, (1) k ₁ ⁰ (2) k ₂ ⁰ Mn^II is observed, while the reaction with S₂O₃ ^2– = 1.5 [(1)], follows one-step second order kinetics with the second order rate constant k = k ⁰ ₁/[S₂O₃ ^2–]. The rate constant k ⁰ ₁ is independent of c _phen ( = [phen] + [Hphen⁺]) but directly proportional to [H⁺] and [S₂O^2– ₃]. Rapid formation of an adduct between (1) and S₂O^2– ₃, followed by rate-determining one-electron, one-proton reduction of the adduct, appears logical. A comproportionation reaction in one of the subsequent rapid steps leads to (2) without any Mn^II co-product. Kinetic dependences for the second step are same to those for an authentic complex of (2), and further support the assigned reaction sequence.     

Kinetics of uncatalysed and Mn2+ -catalysed oxidation of hydrazine by [MnIV 3 (μ-O)4(bipy)4(H2O)2]4+ ion in aqueous acid

In aqueous acid, hydrazine reduces [Mn^IV ₃(-O)₄(bipy)₄(H₂O)₂]⁴⁺, (1), quantitatively to [Mn^III,IV ₂(-O)₂(bipy)₄]³⁺, (2), and Mn²⁺ if [N₂H⁺ ₅] 2 × (stoichiometric amount). At higher [N₂H⁺ ₅], reduction proceeds up to Mn²⁺. The reduction of (1) to (2) is strongly catalysed by Mn²⁺ and the absorbance (A _t ) versus time (t) graphs have sigmoidal shapes. The graphs become steeper with increasing amounts of added Mn²⁺ and N₂H⁺ ₅, but remain unchanged when [H⁺] is changed. The A _t – t graphs, under various experimental conditions, can all be simulated with a single set of second order rate constants, estimated for the individual steps in a proposed reaction scheme, in which the catalytic action of Mn²⁺ involves a one-electron and a two-electron reduced form of (1), but not (1) itself. The absence of any proton-dependence of the reaction rate refutes an electroprotic mechanism and an inner-sphere mechanism appears to be most likely for the reduction of (1) by N₂H⁺ ₅     

Synthesis,spectroscopic, and crystallographic characterizations of an antiferromagnetically coupled,oxobridged trinuclear manganese(IV) cluster [Mn3O4(H2O)2(phen)4](NO3)4 · 3H2O [phen = 1,10-phenanthroline]

Design and synthesis of a triangular manganese compound, [Mn₃O₄(H₂O)₂(phen)₄](NO₃)_4?·?3H₂O (1) with mono-µ-oxo and di-µ-oxo, is described. The complex has been characterized by elemental analysis, spectroscopy, single crystal and powder diffraction measurements, thermogravimetric analysis, etc. Bond Valence Sum calculations and X-ray photoelectron spectroscopy reveal that each manganese at each vertex of the triangle is +IV oxidation state. Variable temperature magnetic measurements show strong antiferromagnetic coupling between metal ions with the following set of parameters: g?=?1.99, J ₁?=??50.0?cm^?1, and J ₂?=??90.2?cm^?1 (where J ₁ describes the interaction across the two mono-µ-oxo bridges and J ₂ is the exchange coupling across the di-µ-oxo bridge). The compound breaks down in three steps when heated from room temperature to 900°C. The final ash of the compound is confirmed by infrared spectrum with standard MnO₂.     

Photochemical reactions of molybdenum and tungsten octacyanometallates(IV) in acidic aqueous media containing 2,2′-bipyridyl or 1,10-phenanthroline

Summary The reaction scheme of acidic photolysis of [M(CN)₈]^4– (M = Mo or W) in the presence of 2,2-bipyridyl (bipy) or 1,10-phenanthroline (phen) based on previous reports, and the present results, is given. In this scheme the formation of [M(CN)₆(N-N)]^2– (M = Mo or W), postulated in the literature to be a main product of photoexcitation of [M(CN)₈]^4– in the presence of bipy or phen, has definitively been excluded. The main cyano-polypyridyl species formed are [MO(CN)₃(N-N)]^– ions which, in acidic solution, undergo further reactions. A new product, [MoO(CN)₂(N-N)₂], resulting from thermal replacement of the cyanide ligand by polypyridyl, has been detected.Author to whom all correspondence should be directed.     

Kinetics of oxidation of phenylhydrazine by a μ-oxo diiron(III,III) complex in acidic aqueous media

Phenylhydrazine (R) quantitatively reduces [Fe₂(μ-O)(phen)₄(H₂O)₂]⁴⁺ (1) (phen?=?1,10-phenanthroline) and its conjugate base [Fe₂(μ-O)(phen)₄(H₂O)(OH)]³⁺ (2) to [Fe(phen)₃]²⁺ in presence of excess 1,10-phenanthroline in the pH range 4.12–5.55. Oxidation products of phenylhydrazine are dinitrogen and phenol. The reaction proceeds through two parallel paths: 1?+?R?→?products (k ₁), 2?+?R?→?products (k ₂); neither RH⁺ nor the doubly deprotonated conjugate base of the oxidant, [Fe₂(μ-O)(phen)₄(OH)₂]²⁺ (3) is kinetically reactive though both are present in the reaction media. At 25.0°C, I?=?1.0?M (NaNO₃), the rate constants are k ₁?=?425?±?10?M^?1?s^?1 and k ₂?=?103?±?5?M^?1?s^?1. An inner-sphere, one-electron, rate-limiting step is proposed.     

Crystal structure of Ir(III) complexes with 1,10-phenanthroline: K[Ir(phen)Cl4]·H2O and (Me4N)[Ir(phen)Cl4]

The crystal structure of two salts of the complex [Ir(phen)Cl₄]^? anion with K⁺ (K[Ir(phen)Cl₄]·H₂O, 1) and Me₄N⁺ ((Me₄N)[Ir(phen)Cl₄], 2) cations is determined. The iridium(III) ion is in a distorted octahedral environment consisting of chloride anions and a bidentate heterocyclic ligand of 1,10-phenanthroline (phen). A crucial role in the formation of the crystal structure of complex 1 belongs to K…Cl contacts, while in the crystal structure of complex 2, the stacking interactions dominate.     

Non-isothermal Decomposition Kinetics of Complexes [ Sm(m-MBA)3 phen]2 and [ Sm(o-MOBA)3 phen] 2·2H2O

Introduction In recent years, there has been considerable interest in complexes formed by lanthanide cations and various benzoate derivatives[1-4], due to their potential application in areas, such as extraction, separation,germicide preparation, catalysis, luminescence, and functional material preparation[5].     

Synthesis and structure of the organoantimony peroxide solvates [Sb4(μ2-O)4(O2)2(C6H3MeO-2,Br-5)8]·1.5C4H8O2 and [Sb4(μ2-O)4(O2)2(C6H3MeO-2,Br-5)8]·6C4H8O2

The organoantimony peroxide (Ar₂SbO)₄(O₂)₂ (Ar = C₆H₃OMe-2, Br-5) was synthesized by the oxidation of Ar3Sb with hydrogen peroxide in the presence or acetoxime or acetophenone oxime in dioxane. The product crystallizes with various content of the solvent molecules in the crystal unit cell [1.5 (I) and 6 (II), respectively]. An X-ray diffraction analysis of the solvates was performed. Four antimony atoms in the peroxide are in the octahedral coordination, and are linked through bridging oxygen atoms and two peroxide groups. The distances Sb-C, Sb-O_bridge, Sb-O_peroxide, O-O and Sb...Sb are 2.117–2.122, 1.960–1.972, 2.193–2.235, 1.461, 1.465 and 3.223–3.237 Å in I, and 2.112, 2.119, 1.957, 1,966, 2.204, 2,246, 1,467, and 3.2439 Å in II.     

Kinetics and mechanism of the oxidation of tris(2,2′-bipyridine)iron(II) and tris(1,10-phenanthroline)iron(II) complexes by nitropentacyanocobaltate(III) in acidic aqueous medium

The kinetics of the oxidation of tris(2,2′-bipyridyl)iron(II) and tris(1,10-phenanthroline)iron(II) complexes ([Fe(LL)₃]²⁺, LL = bipy, phen) by nitropentacyanocobaltate(III) complex [Co(CN)₅NO₂]^3? was investigated in acidic aqueous solutions at ionic strength of I = 0.1 mol dm^?3 (HCl/NaCl). The reactions were carried out at fixed acid concentration ([H⁺] = 0.01 mol dm^?3) and the temperature maintained at 35.0 ± 0.1 °C. Spectroscopic evidence is presented for the protonated oxidant. Protonation constants of 360.43 and 563.82 dm³ mol^?1 were obtained for the monoprotonated and diprotonated Co(III) complexes respectively. Electron transfer rates were generally faster for [Fe(bipy)₃]²⁺ than [Fe(phen)₃]²⁺. The redox complexes formed ion-pairs with the oxidant with increasing concentration of the oxidant over that of the reductant. Ion-pair constants for these reaction were 160.31 and 131.9 dm³ mol^?1 for [Fe(bipy)₃]²⁺ and [Fe(phen)₃]^2+, respectively. The activation parameters measured for these systems have values as follows: ?H ^≠ (kJ K^?1 mol^?1) = +113.4 ± 0.4 and +119 ± 0.3; ?S ^≠ (J K^?1) = +107.6 ± 1.3 and 125.0 ± 1.6; ?G ^≠ (kJ K^?1) = +81 ± 0.4 and +82.4 ± 0.4; and E _a (kJ mol^?1) = 115.9 ± 0.5 and 122.3 ± 0.6 for LL = bipy and phen, respectively. Effect of added anions (Cl^?, $ {\text{SO}}_{4}^{2 - } $ and $ {\text{ClO}}_{4}^{ - } $ ) on the systems showed decrease in the electron transfer rate constant. An outer-sphere mechanism is proposed for the reaction.     

[(phen)2Mn2(μ-O)(μ-Ac)2(H2O)2](ClO4)2·4H2O双核锰配合物的合成、晶体结构及性质

MnAc3.2H2O在pH=4.0的HAc-NaAc缓冲溶液中和邻菲罗啉(phen)反应, 制得了双核锰(Ⅲ)合物[(phen)2Mn2(μ-O)(μ-Ac)2 (H2O)2](ClO4)2.H2O, 并进行了红外光谱表征. X射线单晶衍射表明, 该晶体属单斜晶系, 空间群P21/n, 晶胞参数: a=1.025 28(5) nm, b=1.792 75(9) nm, c=1.984 14(10) nm, β=94.843 0(10)°, V=3.634 0(3) nm3, Z=4, Dc=1.669 g.cm-3. 紫外可见光谱在480 nm处有一个吸收峰. 循环伏安实验说明, 此配合物在乙腈溶液中经历了一个半可逆的一电子氧化还原过程.     

Syntheses and Crystal Structures of Two Trinuclear Iron(Ⅲ) Carboxylate Complexes: [Fe3(μ3-O)(μ-O2CEt)6(H2O)3]Cl.3H2O and [Fe3(μ3-O)(μ-O2CEt)6Py3]Cl(Py=pyridine)

Two new oxo-centered trinuclear iron complexes [Fe3(μ3-O)(μ-O2CEt)6(H2O)3]Cl.3H2O 1 and [Fe3(μ3-O)(μ-O2CEt)6Py3]Cl 2 were prepared in non-aqueous solvent and their crystal structures have been determined. Crystal 1 is monoclinic, space group P21/n, a=9.909(3), b=24.467(8), c=14.542(7)(), β=107.85(4)° V=3356(4)()3, Z=4, Mr=765.52, Dc=1.52 g/cm3, μ=14.28 cm-1, F(000)=1588 and R=0.059, Rw=0.071 for 3745 unique reflections with I>3σ(I). Crystal 2 belongs to the monoclinic system with space group C2/c, a=13.750(3), b=18.439(4), c=16.696(3)(), β=93.42(3)°, V=4226(3)()3, Z=4, Mr=894.73, Dc=1.41 g/cm3, μ=11.4 cm-1, F(000)=2322 and R=0.058, Rw=0.062 for 2272 unique reflections with I>3σ(I). The two structures contain the same trimetal framework in which three iron(Ⅲ) atoms form a nearly equilateral triangle with a μ3-oxygen atom in the centre.     

Nonisothermal Kinetice of Dehydration Process of [Sm(m-CIBA)3phen]2·2H2O and[Sm(p-CIBA)3phen]2·2H2O

Compounds[Sm(m-CIBA)3phen]2·2H2O and[Sm(p-ClBA)3phen]2·2H2O(m-ClBA=m-chlorobenzoate,PClBA=p-chlorobenzoate,phen=1,10-phenanthroline)were prepared.The dehydration processes and kinetics of these compounds were studied from the analysis of the DSC curves using a method of processing the data of thermal analysis kinetics.The Arrhenius equation for the dehydration process can be expressed as lnk=38.65-243.90x103|RT for and△S≠ of dehydration reaction for the title compounds are determined,respectively.     

Kinetics and mechanism of the two electron oxidation of cis-CrIII(dipy)2(H2O)2]3+ (dipy = 2,2′-dipyridyl) by periodate ion to cis-[CrV(dipy)2(O)2]+ in aqueous acidic solutions

The kinetics of oxidation of cis-[Cr^III(dipy)₂(H₂O)₂]³⁺ (dipy = 2,2′-dipyridyl) by IO₄ ^? has been studied in aqueous acidic solutions. The initial oxidation product is certainly not Cr(VI). The isolated solid product is consistent with the formula cis-[Cr^V(dipy)₂(O)₂]IO₄. The Cr(V) product has been isolated and characterized by elemental analysis, IR and ESR spectroscopy. In the presence of a vast excess of [IO₄ ^?], the reaction is first order in the chromium(III) complex concentration. The pseudo-first-order rate constant, k _obs, showed a very small change with increasing [IO₄ ^?]. The dependence of k _obs on [IO₄ ^?] is consistent with Eq. (i). i $$ {\text{k}}_{\text{obs}} = {\text{a}}[{\text{IO}}_{4}^{\text{ - }} ]/({\text{b}} + {\text{c}}[{\text{IO}}_{4}^{\text{ - }} ]) $$ The pseudo-first-order rate constant, k _obs, increased with increasing pH, indicating that the hydroxo form of the chromium(III) complex is the reactive species. An inner-sphere mechanism has been proposed for the oxidation process. The thermodynamic activation parameters of the processes involved are also reported.     

[Mn(phen)2(H2O)2]2[Cr(OX)3][HOCH2CH2O].4H2O的合成、晶体结构及性质

在二甲亚砜(DMSO)中,以MnCl_2·2H_2O和K_3[Cr(OX)_3]·3H_2O为原料,合成了离子型配合物[Mn(phen)_2(H_2O)_2]_2[Cr(OX)_3][HOCH_2CH_2O]·4H_2O.晶体结构测定表明,该晶体属单斜晶系,P2/c空间群.晶体学参数:a=1.0602(3),b=1.3515(3),c=2.1508(3)nm,β=102.57(2)°,V=3.008(1)nm~3,Z=2,Dc=1.49g/cm~3,F(000)=1392.最后的偏差因子R=0.067.测定了化合物的UV-Vis-NIR,IR,XPS,ESR光谱和变温磁化率,讨论了相应的性质.     

A novel manganese(II) complex with phen ligands: hydrothermal synthesis,structure and magnetic properties of [Mn(phen)(H2O)4] SO4·2H2O

A novel manganese(II) complex, [Mn(phen)(H₂O)₄]SO₄·2H₂O (1), has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. The manganese(II) complex contains only one phen ligand and four water ligands. By a catalytic test, complex 1 provided direct evidence that phen is a key ligand instead of an auxiliary one in manganese catalase mimics. Magnetic susceptibility measurements for complex 1 have been performed down to 2?K, suggesting paramagnetic behavior for this complex.     

[Mn(phen)2(H2O)2]2[Cr(OX)3][HOCH2CH2O].4H2O的合成、晶体结构及性质

在二甲亚砜(DMSO)中, 以MnCl2.2H2O和K3[Cr(Ox)3].3H2O为原料, 合成了离子型配合物[Mn(phen)2(H2O)2]2[Cr(OX)3][HOCH2CH2O].4H2O。晶体结构测定表明, 该晶体属单斜晶系, P2/c空间群。晶体学参数: a=1.0602(3),b=1.3515(3), c=2.1508(3)nm, β=102.57(2)°, V=3.008(1)nm^3, Z=2,Dc=1.49g/cm^3, F(000)=1392。最后的偏差因子R=0.067。测定了化合物的UV-Vis-NIR, IR, XPS, ESR光谱和变温磁化率, 讨论了相应的性质。     

Efficient epoxidation of electron-deficient alkenes with hydrogen peroxide catalyzed by [γ-PW10O38V2(μ-OH)2]3-

A divanadium‐substituted phosphotungstate, [γ‐PW₁₀O₃₈V₂(μ‐OH)₂]^3? ( I ), showed the highest catalytic activity for the H₂O₂‐based epoxidation of allyl acetate among vanadium and tungsten complexes with a turnover number of 210. In the presence of I , various kinds of electron‐deficient alkenes with acetate, ether, carbonyl, and chloro groups at the allylic positions could chemoselectively be oxidized to the corresponding epoxides in high yields with only an equimolar amount of H₂O₂ with respect to the substrates. Even acrylonitrile and methacrylonitrile could be epoxidized without formation of the corresponding amides. In addition, I could rapidly (≤10 min) catalyze epoxidation of various kinds of terminal, internal, and cyclic alkenes with H₂O₂ under the stoichiometric conditions. The mechanistic, spectroscopic, and kinetic studies showed that the I ‐catalyzed epoxidation consists of the following three steps: 1) The reaction of I with H₂O₂ leads to reversible formation of a hydroperoxo species [γ‐PW₁₀O₃₈V₂(μ‐OH)(μ‐OOH)]^3? ( II ), 2) the successive dehydration of II forms an active oxygen species with a peroxo group [γ‐PW₁₀O₃₈V₂(μ‐η²:η²‐O₂)]^3? ( III ), and 3) III reacts with alkene to form the corresponding epoxide. The kinetic studies showed that the present epoxidation proceeds via III . Catalytic activities of divanadium‐substituted polyoxotungstates for epoxidation with H₂O₂ were dependent on the different kinds of the heteroatoms (i.e., Si or P) in the catalyst and I was more active than [γ‐SiW₁₀O₃₈V₂(μ‐OH)₂]^4?. On the basis of the kinetic, spectroscopic, and computational results, including those of [γ‐SiW₁₀O₃₈V₂(μ‐OH)₂]^4?, the acidity of the hydroperoxo species in II would play an important role in the dehydration reactivity (i.e., k₃). The largest k₃ value of I leads to a significant increase in the catalytic activity of I under the more concentrated conditions.     

Unusually facile syntheses of [RuII(bpy)3]2+ (bpy = 2,2′-bipyridine) and [RuII(phen)3]2+ (phen = 1,10-phenanthroline)

The salts [Ru^II(L–L)₃](CF₃SO₃)₂ (L–L = bpy or phen) have been prepared in high yields via reactions of [Ru^II(DMF)₆](CF₃SO₃)₂ (DMF = N,N-dimethylformamide), generated in situ by reduction of [Ru^III(DMF)₆]-(CF₃SO₃)₃, with an excess of bpy or phen at room temperature in DMF solutions.