A kinetic study on the iron(III)-promoted aquation of [Cr(C2O4)2(picolinato)]2− and [Cr(C2O4)2(2-pyridineacetato)]2− complexes

Two [Cr(C₂O₄)₂(AB)]^2– type complexes, obtained from the reaction of cis-[Cr(C₂O₄)₂(H₂O)₂]^– with the AB ligand, [AB = picolinic (pyac) or 2-pyridine-ethanoic acid (pyeac) anions], were converted into [Cr(C₂O₄)(pyac)(H₂O)₂]⁰ and [Cr(C₂O₄)(pyeac)(H₂O)₂]⁰ compounds, respectively via Fe^III-induced substitution of the oxalato ligand. The aquation products were separated chromatographically and their spectral characteristics and acid dissociation constants determined. The kinetics of the oxalato ligand substitution were studied with a 10–40 fold excess of Fe^III over [Cr^III] at [H⁺] = 0.2 M and at constant ionic strength 1.0 M (Na⁺, H⁺, Fe³⁺, ClO^– ₄). The reaction rate law is of the form: r = k _obs[Cr^III], where k _obs = kQ[Fe^III]/(1 + Q[Fe^III]). The first-order rate constants (k), preequilibria quotients (Q) and activation parameters derived from the k values have been determined. The reaction mechanism is discussed in terms of a Lewis acid catalyzed (induced) ligand substitution.     

Synthesis and Structure of bis(μ-2-aminopyridine N-oxide)-bis[dichlorocopper(II)]

1 INTRODUCTIONMany complexes of 2-aminopyridine N-oxide (apo) have been characterized by infrared spectra, X-ray powder diffraction spectra, and by magnetic measurements and electronic spectra at liquid nitrogen temperature, but very few of them are their crystal X-ray studies[1~3]. Recently, a number of bridged binuclear copper (II) complexes have been reported, some of which have important potential applications in bioinorganic chemistry and materials[4~6]. Particularly, the complexes …     

Cyclohexyl[trans-1,2-bis(1-indenyl)]zirkonium(IV)dichlorid: Ein chiraler polymerisationskatalysator mit stereochemisch starrer Brücke

Chiral trans-1,2-dimesylcyclohexane (1) reacts with indenylsodium to give trans-1,2-diindenylcyclohexane (2). This ligand precursor was used to prepare a mixture of diastereomeric cyclohexyl-[trans-1,2-bis(1-indenyl)]zirconium(IV) dichlorides (3). In contrast to ethylenebis(1-indenyl) zirconium(IV) dichloride (4), compound 3 catalyses the polymerization of propene with high stereoselectivity, even at polymerization temperatures above 50°C.     

Synthesis of 1,1’-[methylenebis(oxy)]-bis[3-alkyl-3-(2-hydroxyethyl)triaz-1-ene 2-oxides]

Potential NO donors, 1,1’-[methylenebis(oxy)]bis[3-(2-hydroxyethyl)triaz-1-ene 2-oxides], were derived from 3-alkyl-3-(2-acetoxyethyl)-1-chloromethoxytriaz-1-ene 2-oxides and 3-alkyl-1-hydroxy-3-(2-hydroxyethyl)triaz-1-ene 2-oxide sodium salts.     

Silver(I) bromide complexes of the rigid diphosphanes 1,2-bis(diphenylphosphano)benzene (dppbz) and 4,5-bis(diphenylphosphano)-9,9-dimethyl-xanthene (xantphos): Crystal structures of [Ag(μ2-Br)(dppbz)]2, [AgBr(xantphos)] and [AgBr(xantphos)(py2SH)]

Reaction of silver(I) bromide with equimolar amounts of the rigid diphos ligands 1,2-bis(diphenylphosphano)benzene (dppbz) and 4,5-bis(diphenylphosphano)-9,9-dimethyl-xanthene (xantphos) in acetone and acetonitrile led to the corresponding chelates [Ag(μ₂-Br)(dppbz)]₂ (1) and [AgBr(xantphos)] (2). Treatment of 1 and 2 with pyridine-2-thione (py2SH) in ethanol gave the mixed-ligand complexes [AgBr(dppbz)(py2SH)] (3) and [AgBr(xantphos)(py2SH)] (4), respectively. Compounds 1, 2 and 4 have been characterized by X-ray diffraction, establishing distorted tetrahedral or trigonal planar coordination geometries of the silver atoms.     

Metal-phenoxyalkanoic acid interactions—XXIII. Complexes of copper(II) with the phenoxyisobutyric acids. The crystal structures of tetra-μ-[2-methyl-2-(4-chlorophenoxy)propanoato-O,O′)]-bis[(2-aminopyrimidine)copper(II)] and two polyaquacopper(II) tri-μ-[2-methyl-2-phenoxypropanoato-O,O′]-bis[(2-methyl-2-phenoxypropanoato)copper(II)] polymorphs

The crystal structures of three copper(II) complexes with phenoxyisobutyric acid (PIBAH) and p-chlorophenoxyisobutyric acid (PCIBAH) have been determined by X-ray diffraction. Tetra-μ-[2-methyl-2-(4-chlorophenoxy)-propanoato-O,O′]-bis[2-amino-pyrimidine)copper(II)], [Cu₂(PCIBA)₄(2-aminopyrimidine)₂]₂ (1) is a centrosymmetric tetracar☐ylate bridged dimer [Cu⋯Cu, 2.689(2)Å] with the nitrogens of the 2-aminopyrimidine molecules occupying the axial positions [CuN, 2.198(7)Å]. Tetraaquacopper(II) tri-μ-[2-methyl-2-phenoxypropanoato-O,O′]-bis[(2-methyl-2-phenoxypropanoato(copper(II)], [Cu(H₂O)₄]²⁺] {[Cu₂(PIBA)₅]⁻}₂, (2), is a disordered precursor of the stable structure (3), [Cu(H₂O)₅]²⁺ {[Cu₂(PIBA)₅]⁻·4H₂O, consisting of centrosymmetric square planar [Cu(H₂O)₄]²⁺ cations and tris(car☐ylate)-bridged dimer anions [Cu⋯Cu, 2.85(1)Å] (2). The fourth position of each square planar dimer ‘end’ is occupied by a car☐ylate oxygen of a PIBA molecule which also provides the ether oxygen capping each axial dimer site [CuO, 2.15(4), 2.19(5)Å]. This completes a five-membered chelate ring. A symmetrical array of eight hydrogen bonds link the four waters of the [Cu(H₂O)₄]²⁺ cation to the car☐yl oxygens of both the capping PIBA ligands of the two dimeric anions. Structure (3) has essentially identical [Cu₂(PIBA)₅]⁻ dimer anions [Cu⋯Cu, 2.929(1)Å] and hydrogen-bonding interactions with the tetraaquacopper(II) cations. However, water molecules partially occupy the octahedral sites of these cations [CuO, 2.46(1)Å], as well as a number of lattice sites in the crystal.     

The photolytic reaction between [ReN(H2O)(CN)4]2− and 1,2-ethanediamine. The crystal structure of tetraphenylphosphonium μ-1,2-ethanediamine-N,N′-bis[tetracyanonitridorhenate(V)] tetrahydrate

An aqueous solution of [ReN(H₂O)(CN)₄]^2– and 1,2-ethanediamine was irradiated in a photolytic reactor. The reaction product, which was isolated as yellow crystals suitable for X-ray structure determination, is a novel complex with the 1,2-ethanediamine acting as a bridge between two rhenium atoms. The crystal structure of (PPh₄)₄[{ReN(CN)₄}₂(-en)] · 4H₂O was determined from three-dimensional X-ray diffraction data. The [{ReN-(CN)₄}₂(-en)]^4– anion has a distorted octahedral geometry around both rhenium atoms with Re(1) displaced by 0.35 and Re(2) by 0.31 Å towards the respective nitrido ligands from the equatorial planes formed by the carbon atoms of the four cyano ligands of each rhenium atom.     

Synthesis and structures of two uranyl β-diketonate complexes [UO2(DBM)2(DEDPU)] and [UO2(PMBP)2(DEDPU)]

Two new uranyl β-diketonate complexes [UO₂(DBM)₂(DEDPU)] (1) and [UO₂(PMBP)₂(DEDPU)](CH₃C₆H₅)_0.5 (2), (HDBM?=?dibenzoylmethane, HPMBP?=?1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, DEDPU?=?N,N′-diethyl-N,N′-diphenylurea) were synthesized and characterized. The coordination geometries of the uranyl atoms in 1 and 2 are distorted pentagonal bipyramidal, coordinated by one oxygen atom of DBDPU molecule and four oxygen atoms of two chelating DBM molecules in 1 and PMBP molecules in 2.     

Intramolecular [2 + 2] photocycloaddition. 2. Mechanism of intramolecular photocyclization of α,ω-bis(p-vinylphenyl)alkanes

From the photophysical measurements of the title reaction, the formation of cyclophanes is concluded to be facilitated by high microscopic concentration of styrene moieties and depressed by strain loaded at the transition state.     

1- and 2-D NMR Studies on [Rh6C(CO)14(PPh3)]2−

A complete NMR study involving both 1D and 2D ¹³C-{¹⁰³Rh} and ³¹P-{¹⁰³Rh} HMQC measurements, on [Rh₆C(CO)₁₄(PPh₃)]^2- are reported and discussed, together with the multiple Rh quantum effects found for resonances associated with edge- and face-bridging CO's. As found in [Rh₆C(CO)₁₅]^2-, the carbonyl ligands in [Rh₆C(CO)₁₄(PPh₃)]^2- undergo CO-intermolecular exchange with ¹³CO at different rates; for the edge-bridging CO's, the lower the value of ¹J(Rh–CO), the faster the rate of intermolecular exchange with ¹³CO.     

Synthesis and Characterization of Nitrato-Triamine-Metal(II) Complexes. Conglomerate Crystallization Part 55. Crystal Structure of [Ni(dien)(O2NO)(ONO2)] (I), {[Cu(dien)-(μ-ONO2)]NO3}∞ (II), [Zn(dien)(O2NO)(ONO2)] (III), [Ni(Medpt)(O2NO)(ONO2)] (IV) and [Cu(Medpt)(ONO2)2] (V)

In absolute ethanol and in the presence of triethylorthoformate, reactions of metal(II) nitrates with linear tridentate amines afforded metal complexes of the formula M(NNN)(NO₃)₂, where M = Ni²⁺, Cu²⁺ and Zn²⁺, and NNN = dien and Medpt. The compounds fall into three categories in accordance with their stereochemistry and mode of binding of the nitrato ligands. Compounds I, [Ni(dien)(O₂NO)(ONO₂)] and III, [Zn(dien)(O₂NO)(ONO₂)] are isomorphous and isostructural. They crystallize in the monoclinic space group P2₁/n with nearly identical cell constants. The stereochemistry of these two compounds is such that the terdentate dien ligand forms a fac MN₃ moiety with the two oxygens of the bidentate nitrato ligand trans to the terminal NH₂. These ligands form the base of the octahedral arrangement in which the sixth position, trans to the secondary nitrogen of the dien, is an oxygen of the monodentate nitrato ligand. Compound IV, [Ni(Medpt)(O₂NO)(ONO₂)] falls into the same category as I and III despite the fact that the two rings in the Ni-Medpt moiety are six-membered rings, unlike those in compounds I and III which are five-membered rings. Nevertheless, the nickel-amine arrangement is fac. The bidentate nitrato-oxygens are trans to the terminal NH₂ of the amine ligand, and the oxygen of the monodentate nitrato ligand is trans to the tertiary amine-nitrogen. Such stereochemistry is prevalent for nickel and zinc compounds. Interestingly, compound IV crystallizes as a conglomerate (space group P2₁2₁2₁). Compound II, {[Cu(dien)(μ-ONO₂)]NO₃}_∞ belongs to the second category and has a polymeric structure. The repeating fragment in the polymeric chain is a Cu(dien)-O fragment with the monodentate nitrato ligand occupying an equatorial position of the base. A second oxygen of the equatorial nitrate becomes an axial ligand for an adjacent Cu-N₃O fragment. In this way the substance propagates into an infinite chain. The repeating unit has an effective square pyramidal, five-coordinate, configuration. Finally, the compound crystallizes as a racemate. The second nitrate necessary for charge compensation of this copper(II) compound is ionic and its function is to hold the infinite chains of the lattice. The third category represented by compound V, [Cu(Medpt)(ONO₂)₂] contains two molecules in the asymmetric unit of the racemic lattice (monoclinic, space group P2₁/a). The structure of Cu-Medpt is unlike that of IV in that both species present in the asymmetric unit have the amine ligand in a mer configuration which together with a monodentate oxygen of a nitrato ligand form a base plane of a square pyramid. The fifth ligand of both Cu²⁺ ions is a second monodentate nitrato ligand. The stereochemical differences between the two Cu²⁺ ions are insignificant for the Cu-Medpt fragment, which share the same conformation and configuration. The major difference between the two species is the torsional angles defined by the Cu-O-N-O angles. The difference arises from variation in the hydrogens of the primary amine moieties selected by nitrato-oxygens to form intramolecular hydrogen bonds. Finally, there is a little variation in the equatorial Cu-ONO₂ stereochemistry because of steric hindrance, imposed by the Medpt, preventing large torsional angles by these nitrato ligands. This is evident by comparing the two copper species shown in Finally, nitrate-to-Br ligand exchange was found to take place when KBr pellets are prepared for IR spectral measurements.     

Synthesis of 3,3-bis(2-hydroxyethyl) and 3,3,3’-tris(2-hydroxyethyl) derivatives of 1,1’-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides)

Synthetic procedures to access new potential NO donors that can generate NO in living systems, 3,3-bis(2-hydroxyethyl) and 3,3,3’-tris(2-hydroxyethyl) derivatives of 1,1’-[methylenebis(oxy)]bis(3,3-dialkyltriaz-1-ene 2-oxides), were elaborated. 3,3-Bis(2-acetoxyethyl)-1(chloromethoxy)triaz-1-ene 2-oxide reacts with 1-hydroxytriaz-1-ene 2-oxide sodium salts to give a series of alkylated 3,3-bis(2-acetoxyethyl) derivatives. Deacetylation of the latter produces 3-(2-hydroxyethyl)-11,11-dialkyl-6,8-dioxa-3,4,5,9,10,11-hexaazaundeca-4,9-dien-1-ol 4,10-dioxides and 11-alkyl-3-(2-hydroxyethyl)-6,8-dioxa-3,4,5,9,10,11-hexaazatrideca-4,9-diene-1,13-diol 4,10-dioxides.     

Synthesis of 3,3-bis(2-haloethyl) and 3,3,3′-tris(2-haloethyl) derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides)

Synthetic procedures towards 3,3-bis(2-haloethyl) and 3,3,3′-tris(2-haloethyl) derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides) via halogenation of the corresponding 2-hydroxyethyl derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides) and iodination of the corresponding 2-bromoethyl derivatives were elaborated. The synthesized compounds are promising NO donors in the living organisms.     

H_8[P_2Mo_(17)Co(OH_2)O_(61)]和H_8[P_2Mo_(17)Ni(OH_2)O_(61)]的抑酶活性研究

合成了2种过渡金属取代的多酸H_8[P_2Mo_(17)Co(OH_2)O_(61)]和H_8[P_2Mo_(17)Ni(OH_2)O_(61)],并对其抑酶活性进行了研究.结果表明,这2种化合物对酪氨酸酶均有有效的抑制效果.抑制机理表明2种化合物均是可逆竞争型抑制剂.H_8[P_2Mo_(17)Co(OH_2)O_(61)]和H_8[P_2Mo_(17)Ni(OH_2)O_(61)]的半抑制率IC_(50)值分别为(0.434 0±0.000 4)和(0.466 5±0.012 0)mmol/L,抑制常数K_Ⅰ分别为0.216 7和0.220 4mmol/L.该研究能够扩大多金属氧酸盐的应用范围.     

[Cu(Bphe)_2(phen)]·H_2O的晶体结构

Cu（phen）Cl2与N-苯甲酰朱丙氨酸（Bphe）在水溶液中的取代反应生成了铜配合物[Cu（Bphe）2（phen）]·H2O。晶体属单科晶系，C2／c空间群。晶胞参数：a-5．330（1），分子计算式：mm－1。全矩阵最小二乘法修正，结构因子中心原子Cu与2个Bphe配体的O（3）、O（3A）及phen分子的2个N原子形成4配位的近似平面四边形结构。     

配合物[UO2(PMBP)2(DMDBU)]的合成和晶体结构

1-苯基-3-甲基-4-苯甲酰基-吡唑啉酮-5(HPMBP)是一类含有氮杂环的β-二酮螯合剂,现在已经广泛应用于金属离子的分离和分析[1-4]。最近我们采用取代脲N,N-二甲基-N,N-二苯基脲(DMDBU)和N,N-二乙基-N,N-二苯基脲(DED-BU)应用于铀(VI)和钍(IV)萃取研究,并合成和测定了配合物[UO2(D     

Synthesis,crystal structure,and properties of [Cu(LH)]2[M(mnt)2] [M = Ni or Cu; H2L = 3,3′-(1,3-propanediyldinitrilo)-bis(2-butanone oxime); mnt2− = maleonitriledithiolate] complexes containing bridging cyano groups

Interesting complexes containing a mnt^2– bridge, based on the reaction of [M(mnt)₂]^2– [M = Ni or Cu] with [Cu(LH)]⁺, have been prepared and characterized by e.s.m.s., i.r and u.v–vis. spectroscopic techniques and by electrochemistry. The complexes show weak antiferromagnetic interactions between magnetic centers. The X-ray analysis of the molecular structure of [Cu(LH)]₂[Ni(mnt)₂] has been completed. It structurally features the CN group of mnt^2– which can act as a bridging ligand between two transition metals.     

Water-Tolerant Superbase Polyoxometalate [H2(Nb6O19)]6− for Homogeneous Catalysis

Here, doubly protonated Lindqvist-type niobium oxide cluster [H₂(Nb₆O₁₉)]^6–, fabricated by microwave-assisted hydrothermal synthesis, exhibited superbase catalysis for Knoevenagel and crossed aldol condensation reactions accompanied by activating C−H bond with pK_a >26 and proton abstraction from a base indicator with pK_a=26.5. Surprisingly, [H₂(Nb₆O₁₉)]⁶⁻ exhibited water-tolerant superbase properties for Knoevenagel and crossed aldol condensation reactions in the presence of water, although it is well known that the strong basicity of metal oxides and organic superbase is typically lost by the adsorption of water. Density functional theory calculation revealed that the basic surface oxygens that share the corner of NbO₆ units in [H₂(Nb₆O₁₉)]⁸⁻ maintained the negative charges even after proton adsorption. This proton capacity and the presence of un-protonated basic sites led to the water tolerance of the superbase catalysis.     

Synthesis and Crystal Structure of Potassium Triethylenetetraaminehexaacetatodi [Oxo-vanadium(Ⅳ)] Hexahydrate, K_2[V_2O_2(ttha)]·6(H_2O)

1 INTRODUCTION Interest in vanadium in the physiology and biochemistry has promoted enormously in recent years. Vanadium is known to exist in alternative nitrogenase metalloenzyme systems fixing nitrogen. It is also found to participate in biological processes exhibiting mitogenic behavior and enzyme inhi- bition[1]. Up to date, several crystal structures have been reported about vanadium with carboxylic or polycarboxylic acid[2, 3]. However, very few struc- tures of vanadium complexes …     

Crystal Structure Analysis of Tetras[L-tris(ethylenediamine) cobalt(Ⅲ)] tris[hexacyanoruthenate(Ⅱ)]

1 INTRODUCTION The tris(ethylenediamine) cobalt (Ⅲ) complex in which there are L and D configurations is one of the very interest cations due to the chirality among research complexes and the characterization of reaction on the ion-pair charge-transfer transitions. It has been mentioned in a lot of examples on the chirality and the structure, such as [L-Co(en)3]- [?Co(edta)]2Cl?0H2O[1], [(+)DCo(en)3]Cl3稨2O[2], [(+)-Co(en)3?-)-Cr(en)3]Cl?.1H2O[3], [()-Co(en)3] (SCN)3[4], [(+)D…