Zirconium(IV) catalysis in perborate oxidation of iodide

Zirconium(IV) catalyzes perborate oxidation of iodide ion. In acidic solution the oxidation is zero order with respect to perborate, first order with respect to Zr(IV), independent of [H⁺] and exhibits Michaelis-Menten dependence on [I⁻]. Mechanistic pathway of the catalysis is discussed and a rate equation is derived.     

From 1D to 2D Cd(II) and Zn(II) Coordination Networks by Replacing Monocarboxylate with Dicarboxylates in Partnership with Azine Ligands: Synthesis,Crystal Structures,Inclusion, and Emission Properties

Eight mixed-ligand coordination networks, [Cd(2-aba)(NO₃)(4-bphz)_3/2]_n·n(dmf) (1), [Cd(2-aba)₂(4-bphz)]_n·0.75n(dmf) (2), [Cd(seb)(4-bphz)]_n·n(H₂O) (3), [Cd(seb)(4-bpmhz)]_n·n(H₂O) (4), [Cd(hpa)(3-bphz)]_n (5), [Zn(1,3-bdc)(3-bpmhz)]_n·n(MeOH) (6), [Cd(1,3-bdc)(3-bpmhz)]_n ·0.5n(H₂O)·0.5n(EtOH) (7), and [Cd(NO₃)₂(3-bphz)(bpe)]_n·n(3-bphz) (8) were obtained by interplay of cadmium nitrate tetrahydrate or zinc nitrate hexahydrate with 2-aminobenzenecarboxylic acid (H(2-aba)), three dicarboxylic acids, sebacic (decanedioic acid, H₂seb), homophthalic (2-(carboxymethyl)benzoic acid, H₂hpa), isophthalic (1,3-benzenedicarboxylic acid, H₂(1,3-bdc)) acids, bis(4-pyridyl)ethane (bpe) and with four azine ligands, 1,2-bis(pyridin-4-ylmethylene)hydrazine (4-bphz), 1,2-bis(1-(pyridin-4-yl)ethylidene) hydrazine (4-bpmhz), 1,2-bis(pyridin-3-ylmethylene)hydrazine (3-bphz), and 1,2-bis(1-(pyridin-3-yl) ethylidene)hydrazine (3-bpmhz). Compounds 1 and 2 are 1D coordination polymers, while compounds 3–8 are 2D coordination polymers. All compounds were characterized by spectroscopic and X-ray diffraction methods of analysis. The solvent uptakes and stabilities to the guest evacuation were studied and compared for 1D and 2D coordination networks. The de-solvated forms revealed a significant increase of emission in comparison with the as-synthesized crystals.     

Formation of Zirconium(IV)–Heparin Complex Multilayers on Solid Surfaces for Long‐Lasting Antiplatelet Application

A facile approach to enhancing the blood compatibility of solid surfaces based on Zr^IV–heparin complexation is reported. Solid surfaces are pretreated with tannic acid (TA)/Zr^IV complexes. Heparin is then deposited on the surface through a spin‐coating process and fixed by a Zr^IV‐mediated crosslinking reaction. Using this approach, TA/Zr^IV/heparin complex multilayers that are highly resistant to human platelet adhesion are formed on various substrates including metal, metal oxides, ceramics, and synthetic polymers. This approach presents a sustainable way for the immobilization of heparin onto surfaces because it does not require any derivatization of heparin molecule as well as time‐consuming processes.     

Cation-Controlled Assembly of Polyoxotungstate-Based Coordination Networks

The Preyssler polyoxoanion, [NaP₅W₃₀O₁₁₀]¹⁴⁻ ({P₅W₃₀}), is used as a platform for evaluating the role of nonbridging cations in the formation of transition-metal-bridged polyoxometalate (POM) coordination frameworks. Specifically, the assembly architecture of Co²⁺-bridged frameworks is shown to be dependent on the identity and amount of alkali or alkaline-earth cations present during crystallization. The inclusion of Li⁺, Na⁺, K⁺, Mg²⁺, or Ca²⁺ in the framework synthesis is used to selectively synthesize five different Co²⁺-bridged {P₅W₃₀} structures. The influence of the competition between K⁺ and Co²⁺ for binding to {P₅W₃₀} in dictating framework assembly is evaluated. The role of ion pairing on framework assembly structure and available void volume is discussed. Overall, these results provide insight into factors governing the ability to achieve controlled assembly of POM-based coordination networks.     

三(烃硅基亚甲基)锡不饱和羧酸酯的研究

1986年Tacke将硅原子引进高效杀螨剂Torque——[(PhMe_2CCH_2)_3Sn]_2O,合成了具有同样生物活性的含硅类似物Silyl-Torque——[(PhMe_2SiCH_2)_3Sn]_2O.作者也曾报道三[(苯基二甲硅基)亚甲基]锡羧酸酯的合成,本文在此基础上合成了7个三[(苯基二甲硅     

Titanium(IV) and Zirconium(IV) Sulfato Complexes Containing the Kläui Tripodal Ligand: Molecular Models of Sulfated Metal Oxide Surfaces

Treatment of titanyl sulfate in about 60 mM sulfuric acid with NaL_OEt (L_OEt^?=[(η⁵‐C₅H₅)Co{P(O)(OEt)₂}₃]^?) afforded the μ‐sulfato complex [(L_OEtTi)₂(μ‐O)₂(μ‐SO₄)] ( 2 ). In more concentrated sulfuric acid (>1 M ), the same reaction yielded the di‐μ‐sulfato complex [(L_OEtTi)₂(μ‐O)(μ‐SO₄)₂] ( 3 ). Reaction of 2 with HOTf (OTf=triflate, CF₃SO₃) gave the tris(triflato) complex [L_OEtTi(OTf)₃] ( 4 ), whereas treatment of 2 with Ag(OTf) in CH₂Cl₂ afforded the sulfato‐capped trinuclear complex [{(L_OEt)₃Ti₃(μ‐O)₃}(μ₃‐SO₄){Ag(OTf)}][OTf] ( 5 ), in which the Ag(OTf) moiety binds to a μ‐oxo group in the Ti₃(μ‐O)₃ core. Reaction of 2 in H₂O with Ba(NO₃)₂ afforded the tetranuclear complex (L_OEt)₄Ti₄(μ‐O)₆ ( 6 ). Treatment of 2 with [{Rh(cod)Cl}₂] (cod=1,5‐cyclooctadiene), [Re(CO)₅Cl], and [Ru(tBu₂bpy)(PPh₃)₂Cl₂] (tBu₂bpy=4,4′‐di‐tert‐butyl‐2,2′‐dipyridyl) in the presence of Ag(OTf) afforded the heterometallic complexes [(L_OEt)₂Ti₂(O)₂(SO₄){Rh(cod)}₂][OTf]₂ ( 7 ), [(L_OEt)₂Ti(O)₂(SO₄){Re(CO)₃}][OTf] ( 8 ), and [{(L_OEt)₂Ti₂(μ‐O)}(μ₃‐SO₄)(μ‐O)₂{Ru(PPh₃)(tBu₂bpy)}][OTf]₂ ( 9 ), respectively. Complex 9 is paramagnetic with a measured magnetic moment of about 2.4 μ_B. Treatment of zirconyl nitrate with NaL_OEt in 3.5 M sulfuric acid afforded [(L_OEt)₂Zr(NO₃)][L_OEtZr(SO₄)(NO₃)] ( 10 ). Reaction of ZrCl₄ in 1.8 M sulfuric acid with NaL_OEt in the presence Na₂SO₄ gave the μ‐sulfato‐bridged complex [L_OEtZr(SO₄)(H₂O)]₂(μ‐SO₄) ( 11 ). Treatment of 11 with triflic acid afforded [(L_OEt)₂Zr][OTf]₂ ( 12 ), whereas reaction of 11 with Ag(OTf) afforded a mixture of 12 and trinuclear [{L_OEtZr(SO₄)(H₂O)}₃(μ₃‐SO₄)][OTf] ( 13 ). The Zr^IV triflato complex [L_OEtZr(OTf)₃] ( 14 ) was prepared by reaction of L_OEtZrF₃ with Me₃SiOTf. Complexes 4 and 14 can catalyze the Diels–Alder reaction of 1,3‐cyclohexadiene with acrolein in good selectivity. Complexes 2 – 5 , 9 – 11 , and 13 have been characterized by X‐ray crystallography.     

Covalent Adaptable Networks with Tunable Exchange Rates Based on Reversible Thiol–yne Cross‐Linking

The design of covalent adaptable networks (CANs) relies on the ability to trigger the rearrangement of bonds within a polymer network. Simple activated alkynes are now used as versatile reversible cross‐linkers for thiols. The click‐like thiol–yne cross‐linking reaction readily enables network synthesis from polythiols through a double Michael addition with a reversible and tunable second addition step. The resulting thioacetal cross‐linking moieties are robust but dynamic linkages. A series of different activated alkynes have been synthesized and systematically probed for their ability to produce dynamic thioacetal linkages, both in kinetic studies of small molecule models, as well as in stress relaxation and creep measurements on thiol–yne‐based CANs. The results are further rationalized by DFT calculations, showing that the bond exchange rates can be significantly influenced by the choice of the activated alkyne cross‐linker.     

Group IV M‐POSS (M=Zr,Hf) Coordination Polymers

The synthesis and characterization of Zr‐POSS and Hf‐POSS coordination polymers were reported. The IR data and the solid‐state ²⁹Si MAS NMR indicated the existence of Si? O? M linkage. The polarized optical microscopy images and the XRD data suggested their crystalline nature.     

Preparation, Crystal Structure and Thermal Behaviour of a One-dimensional Coordination Polymer [Mn（m-CPOAH）2（H2O）2]n

1 INTRODUCTION Supramolecular chemistry of manganese(II) car- boxylate coordination polymers has been inten- sively studied in recent years, within which ligand design is an important aspect in adjusting the coordi- nation framework and functionalities of the complexes formed[1～4]. Carboxyphenoxyacetic acids (CPOAH2), which have been known to show biological activities and are widely used in agriculture, are a family of multidentate flexible ligands with versatile binding abilities. …     

Interaction of Alkyltin(IV) Compounds with Ligands of Interest in the Speciation of Natural fluids: Complexes of (CH3)2Sn2+ with Carboxylates

Complex formation by (CH₃)₂Sn²⁺ with acetate (ac), malonate (mal), 1,2,3-propane-tricarboxylate (tricarballylate, tca) and 1,2,3,4-butanetetracarboxylate (btc) ligands in aqueous solution is reported. The study has been performed by potentiometry ([H⁺]–glass electrode) at T=25 °C, and in the 0⩽I⩽1 mol dm⁻³ ionic strength range. In order to evaluate the salt effects on the formation constants of the complex species, and to contribute to the definition of the chemical speciation of diorganotin(IV) compounds in natural waters where carboxylic ligands are naturally present, interactions of NaCl (which is the major component of all natural fluids), with the components of the systems under investigation have also been considered. A model for the ionic strength dependence of the formation constant was used in order to calculate the values of thermodynamic constants, at infinite dilution, for all the proposed species, by considering hydrolytic species too. A relationship between the charges on the different ligands considered and the stabilities of the complex species formed is also discussed. © 1997 John Wiley & Sons, Ltd.     

Spectroscopic and X‐ray structural characterization of new polymeric organotin(IV) carboxylates and their in vitro antifungal activities: Part II

The reactions of R₃SnCl (R = Me, Bu or Ph) with sodium 4‐phenylbutyrate, Na(OPh^b), in EtOH yielded three polymeric triorganotin carboxylates, namely [R₃Sn(OPh^b)]_n (R = Me ( 1 ), Bu ( 2 ) or Ph ( 3 )). All complexes were spectroscopically characterized using Fourier transform infrared, ¹¹⁹Sn Mössbauer, ¹H NMR, ¹³C{¹H} NMR and ¹¹⁹Sn{¹H} NMR spectral techniques. In addition, the crystal structures of 1 and 3 were determined using single‐crystal X‐ray diffraction. Their polymeric structures are sustained by bridging carboxylates which connect two five‐coordinate Sn(IV) centres. Each metallic cation displays a distorted trigonal bipyramidal coordination geometry (Addison's parameters ranging from 0.84 in 1 to 0.77–0.91 in 3 ), with the oxygen atoms occupying the apical positions and the organic groups at the equatorial corners. The one‐dimensional zigzag chains of 1 propagate along the b ‐axis, whereas 3 displays wave‐like double polymeric chains along the b ‐axis. For both 1 and 3 , parallel one‐dimensional polymeric chains are interconnected by C─H⋅⋅⋅π interactions. The antifungal activity of 1 – 3 was screened against Candida albicans (ATCC 18804), C. tropicalis (ATCC 750), C. glabrata (ATCC 90030), C. parapsilosis (ATCC 22019), C. lusitaniae (CBS 6936) and C. dubliniensis (clinical isolate 28). The antifungal activity of 3 was noteworthy since it was not only more active than 1 and 2 , but also more active than the control drugs (nystatin and fluconazole nitrate) in some cases.     

Hydrolysis of Peptide Bonds in Protein Micelles Promoted by a Zirconium(IV)-Substituted Polyoxometalate as an Artificial Protease

The development of artificial proteases is challenging, but important for many applications in modern proteomics and biotechnology. The hydrolysis of hydrophobic or unstructured proteins is particularly difficult due to their poor solubility, which often requires the presence of surfactants. Herein, it is shown that a zirconium(IV)-substituted Keggin polyoxometalate (POM), (Et₂NH₂)₁₀[Zr(α-PW₁₁O₃₉)₂] ( 1 ), is able to selectively hydrolyze β-casein, which is an intrinsically unstructured protein at pH 7.4 and 60 °C. Four surfactants (sodium dodecyl sulfate (SDS), N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (ZW3-12), 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), and polyethylene glycol tert-octylphenyl ether (TX-100)), which differ in the nature of their polar groups, were investigated for their role in influencing the selectivity and efficiency of protein hydrolysis. Under experimental conditions, β-casein forms micellar structures in which the hydrophilic part of the protein is water accessible and able to interact with 1 . Identical fragmentation patterns of β-casein in the presence of 1 were observed through SDS poly(acrylamide) gel electrophoresis both in the presence and absence of surfactants, but the rate of hydrolysis varied, depending on the nature of surfactant. Whereas TX-100 surfactant, which has a neutral polar head, caused only a slight decrease in the hydrolysis rate, stronger inhibition was observed in the presence surfactants with charges in their polar heads (CHAPS, ZW3-12, SDS). These results were consistent with those of tryptophan fluorescencequenching studies, which showed that the binding between β-casein and 1 decreased with increasing repulsion between the POM and the polar heads of the surfactants. In all cases, the micellar structure of β-casein was not significantly affected by the presence of POM or surfactants, as indicated by circular dichroism spectroscopy.     

Coordination Chemistry of Homoleptic Actinide(IV)–Thiocyanate Complexes

The synthesis, X‐ray crystal structure, vibrational and optical spectroscopy for the eight‐coordinate thiocyanate compounds, [Et₄N]₄[Pu^IV(NCS)₈], [Et₄N]₄[Th^IV(NCS)₈], and [Et₄N]₄[Ce^III(NCS)₇(H₂O)] are reported. Thiocyanate was found to rapidly reduce plutonium to Pu^III in acidic solutions (pH<1) in the presence of NCS^?. The optical spectrum of [Et₄N][SCN] containing Pu^III solution was indistinguishable from that of aquated Pu^III suggesting that inner‐sphere complexation with [Et₄N][SCN] does not occur in water. However, upon concentration, the homoleptic thiocyanate complex [Et₄N]₄[Pu^IV(NCS)₈] was crystallized when a large excess of [Et₄N][NCS] was present. This compound, along with its U^IV analogue, maintains inner‐sphere thiocyanate coordination in acetonitrile based on the observation of intense ligand‐to‐metal charge‐transfer bands. Spectroscopic and crystallographic data do not support the interaction of the metal orbitals with the ligand π system, but support an enhanced An^IV–NCS interaction, as the Lewis acidity of the metal ion increases from Th to Pu.     

二（胍基）锆配合物的合成和表征

Addition of one equivalent of LiN（i-Pr）2 or LiN（CH2）5 to carbodiimides, RN=C=NR [R=cyclohexyl （Cy）, isopropyl （i-Pr）], generated the corresponding lithium of tetrasubstituted guanidinates {Li[RNC（N R^′2）NR]（THF）}2 [R=i-Pr, N R^′2=N（i-Pr）2 （1）, N（CH2）5 （2）; R=Cy, N R^′2=N（i-Pr）2 （3）, N（CH2）5 （4）]. Treatment of ZrCl4 with freshly prepared solutions of their lithium guanidinates provided a series of bis（guanidinate） complexes of Zr with the general formula Zr[RNC（N R^′2）NR]2Cl2 [R=i-Pr, N R^′2=N（i-Pr）2 （5）, N（CH2）5 （6）; R=Cy, N R^′2=N（i-Pr）2 （7）, N（CH2）5 （8）]. Complexes 1, 2, 5-8 were characterized by elemental analysis, IR and ^1H NMR spectra. The molecular structures of complexes 1, 7 and 8 were further determined by X-ray diffraction studies.     

PVC热稳定剂——羧酸疏基乙酯锑的合成及性质

以Sb2O3和HSCH2CH2OH为原料合成Sb(SCH2CH2OH)3;再将Sb(SCH2CH2OH)3与RCOOH反应,以钛酸丁酯作催化剂,二甲苯为溶剂,加热回流反应,得到酯锑。产品的热稳定性能测试表明：当逆酯锑的添 加量为2％时,PVC树脂的热稳定时间为8－40min(200℃）。还对该类热稳定剂对PVC的热稳定机理进行了初步探讨。