聚-4-氧杂-6,7-二甲硒基庚基硅氧烷钯(0)配合物的合成及其催化性能研究

4 氧杂 6,7 二氯庚基三甲氧基硅烷依次与气相法二氧化硅、甲硒基钠、氯化钯作用 ,然后用水合肼还原 ,合成了二氧化硅负载的聚 4 氧杂 6,7 二甲硒基庚基硅氧烷钯 ( 0 )配合物 .该配合物是苯乙烯及丙烯酸的Heck芳基化反应的有效催化剂 ,为立体选择性地合成各种取代的反式 1,2 二苯乙烯及反式肉桂酸提供了简便且实用的新方法 .     

Electrochemical behaviour ofcis-dichloro(arylisocyanide)(tertiaryphosphine) platinum (II) and palladium(II) complexes in an aprotic solvent

Summary The electrochemical behaviour of neutral platinum(II) and palladium(II) isocyanide complexes has been investigated in an aprotic medium at platinum and mercury electrodes. Platinum(II) derivatives are reduced to platinum(0) species, Palladium(II) compounds give rise to palladium(0) species at room temperature, while at 0° it is possible to obtain palladium(I) compounds.     

Oscillopolarography of Palladium(II)–Tropeolin 0 Complexes

The electrochemical behavior of palladium(II) complexes of Tropeolin 0 (Tr0) was studied by linear-potential-sweep voltammetry in acetate–ammonia buffer solutions. The optimum conditions for determining palladium(II) with Tr0 were found. The composition of the complex was found to be Pd : Tr0 = 1 : 2. A procedure was proposed for determining palladium(II) with a detection limit of 2.54 × 10^–7M. The procedure was used for determining palladium(II) in capacitors.     

A coordinatively unsaturated,polymer-bound palladium(0) complex. Synthesis and catalytic activities

A coordinatively unsaturated palladium(0) complex was prepared by the reduction of a polymer-bound palladium(II) chloride complex, which was prepared by the reaction of poly-4-diphenylphosphinomethylstyrene with palladium chloride, with hydrazine in ethanol in the presence of triphenylphosphine. Catalytic activities of the polymerbound palladium(0) complex were examined for three representative types of palladium(0)-induced reactions involving oxidative addition of halides to the metal: (i) vinylic hydrogen substitutions with aryl halides, (ii) acetylenic hydrogen substitutions with aryl halides, (iii) vinylic halogen substitutions with Grignard reagents. Use of the catalyst resulted in formation of corresponding products in good yields. The catalytic activity is comparable to that of analogous homogeneous catalysts, yet is not remarkably lowered on being recycled.     

A novel ratiometric sensor for the fast detection of palladium species with large red-shift and high resolution both in aqueous solution and solid state

A highly selective fluorescent probe (OHBT) was designed and synthesized by linking the ESIPT fluorophore N-(3-(benzo[d]thiazol-2-yl)-4-(hydroxyphenyl) benzamide) (HBTBC) to the palladium specificity response group, allyl group, for the detection of palladium species in aqueous solution. The allyl group can be hydrolyzed by Pd⁰ species through the Pd⁰-catalyzed Tsuji–Trost reaction and thus release the fluorophore HBTBC, which shows two emission bands. The maximum emission spectra originated from the enol and keto forms at 415 and 555 nm respectively and with no overlap, which implies the high resolution of the palladium detection. The palladium species can also be detected by paper strip because of the solid-state fluorescence of probe HOBT catalyzed by palladium. This method was successfully applied in the palladium related Suzuki–Miyaura coupling reaction and the detection limit is lower than 1 μM.     

Ion- and atom-leaching mechanisms from palladium nanoparticles in cross-coupling reactions

Leaching of palladium species from Pd nanoparticles under C--C coupling conditions was observed for both Heck and Suzuki reactions by using a special membrane reactor. The membrane allows the passage of palladium atoms and ions, but not of species larger than 5 nm. Three possible mechanistic scenarios for palladium leaching were investigated with the aim of identifying the true catalytic species. Firstly, we examined whether or not palladium(0) atoms could leach from clusters under non-oxidising conditions. By using our membrane reactor, we proved that this indeed happens. We then investigated whether or not small palladium(0) clusters could in fact be the active catalytic species by analysing the reaction composition and the palladium species that diffused through the membrane. Neither TEM nor ICP analysis supported this scenario. Finally, we tested whether or not palladium(II) ions could be leached in the presence of PhI by oxidative addition and the formation of [Pd(II)ArI] complexes. Using mass spectrometry, UV-visible spectroscopy and 13C NMR spectroscopy, we observed and monitored the formation and diffusion of these complexes, which showed that the first and the third mechanistic scenarios were both possible, and were likely to occur simultaneously. Based on these findings, we maintain that palladium nanoparticles are not the true catalysts in C--C coupling reactions. Instead, catalysis is carried out by either palladium(0) atoms or palladium(II) ions that leach into solution.     

Synthesis of imprinted polymer material with palladium ion nanopores and its analytical application

Ion imprinted polymer (IIP) materials with nanopores were prepared by formation of ternary complex of palladium imprint ion with dimethylglyoxime (DMG) and 4-vinylpyridine (VP, functional monomer) and thermally copolymerizing with styrene (crosslinking monomer) and divinylbenzene (cross linker) and 2,2′-azobisisobutyronitrile as initiator. The synthesis was carried out with cyclohexanol as porogen and subsequently leached with 50% (v/v) HCl to obtain leached IIP particles. These leached IIP particles can now pick up palladium ions from dilute aqueous solutions. The optimal acidity for quantitative enrichment was 0.2-0.4N HCl and eluted completely by stirring for 15 min with 2×10 ml of 50% (v/v) HCl. The palladium ion imprinting polymer gave 100 times higher distribution ratio than ion recognition (blank) polymer (IRP). Further, percent extraction, distribution ratio and selectivity coefficients of palladium and other selected inorganic ions using IRP and IIP particles were determined and compared. Five replicate determinations of 50 μg of palladium in 1 l of solution gave a mean absorbance of 0.200 with a relative standard deviation of 2.12%. The detection limit corresponding to three times the standard deviation of the blank was 2.5 μg of palladium/l.     

Carbonyl allylation of aldehydes catalyzed by a silica-supported poly-γ-diphenylarsinopropylsiloxane palladium(0) complex

A silica-supported poly-γ-diphenylarsinopropylsiloxane palladium(0) complex has been prepared from γ-chloropropyltriethoxysilane via immobilization on fumed silica, followed by reacting with potassium diphenylarsenide and palladium chloride, and then the reduction with hydrazine hydrate. The palladium(0) complex has been found to catalyze the allylation of aldehydes via the formation of π-allylpalladium complexes, using allylic chlorides as allylating agent and SnCl₂ as reducing agent. This polymeric palladium complex can be recovered and reused.     

催化动力学光度法测定痕量钯

在磷酸－磷酸二氢钾缓冲溶液中，以钯（Ⅱ）催化次磷酸钠还原罗丹明Ｂ褪色为指示反应，建立了痕量钯的动力学光度分析新方法。在金（Ⅱ）的存在下，检测下限达５×１０＾－１１ｇ／ｍＬ钯（Ⅲ），方法应用于模拟合金样和含钯分子筛中钯的测定。结果满意。     

壳聚糖钯(0)配合物催化Heck芳基化反应研究

以天然高分子壳聚糖为载体,室温下通过与氯化钯乙醇溶液作用制得壳聚糖负载氯化钯黄色粉末,再在乙醇溶液中回流还原,制得了壳聚糖钯(0)配合物催化剂,研究了其对碘代苯与丙烯酸Heck芳基化反应的催化性能.结果表明该催化剂具有较高的催化活性和立体选择性,可高转化率、高产率地合成反式苯丙烯酸;通过简单的过滤、溶剂洗涤回收催化剂,并能多次重复使用.该催化剂对其它反应底物的催化性能也进行了探讨.     

A Versatile Palladium Synthon: [Pd(NHC)(PhC≡CPh)]**

The synthesis and isolation of [Pd(NHC)(PhC≡CPh)] complexes are reported. These new 14-electron Pd(0)-complexes are key synthons leading to known palladium(0) and palladium(II) species, as well as permitting access to unprecedented mixed NHC-phosphite palladium(0) complexes. This motif permits the facile catalytic hydrosilylation of allenes. DFT calculations have allowed the characterization of the relatively weak interaction between the metal and the diphenylacetylene ligand, with a comparison with a series of ligands with more or less coordinating power, bearing varied structural and electronic properties.     

Fixation of both O2 and CO2 from air by a crystalline palladium complex bearing N-heterocyclic carbene ligands

Crystals of the two-coordinate palladium(0) complex 1 bearing the new N-heterocyclic carbene ligand, ITmt, directly and rapidly fixed both O2 and CO2 from air to produce the corresponding palladium(II) peroxocarbonate complex 2. The present reaction consists of dioxygenation of the palladium(0) complex 1 to the palladium(II) peroxo complex 3 and the subsequent CO2 insertion to produce the peroxocarbonate complex 2. Reaction of the crystals of 1 with air was monitored by microscopic IR spectroscopy to confirm the sequence of the two-step solid-state reaction. The unique reactivity of solid 1 toward air was explained in terms of the structural features of the carbene ligand, ITmt.     

Formation of palladium phosphides in the reaction of bis(dibenzylideneacetone)palladium(0) with white phosphorus

The reaction of bis(dibenzylideneacetone)palladium(0) with white phosphorus was studied using the methods of NMR, UV spectroscopy, and X-ray powder diffraction. The products of the reaction are shown to be palladium phosphides, their composition depending on the ratio of the reagents. The mechanism of the formation of the palladium-enriched phosphides is suggested, which includes the formation of palladium diphosphide PdP₂ that subsequently reacts with the excess of bis(dibenzylideneacetone)palladium(0) leading to palladium phosphides Pd₅P₂, Pd₃P_0.8, Pd_4.8P, and free dibenzylideneacetone.     

Detection and reactivity of a palladium alkoxycarbene

A characterful carbene: The high electrophilicity of a genuine palladium alkoxycarbene, obtained by transmetalation, is evident in its reactivity. Nucleophilic attack on two electrophilic centers (red) is observed. Alkyl abstraction and addition to the carbene carbon by different nucleophiles occur. This palladium(II) alkoxycarbene also undergoes comproportionation with palladium(0) to give an unprecedented palladium(I) dimeric carbene (see scheme).     

Formation of Nanosized Catalysts Based on Palladium Phosphine Complexes and the Nature of Their Activity

Findings on the formation and features of nanosized particles based on palladium complexes, which are active in hydrogenation catalysis, are summarized. Depending on the nature of a reducing agent, nanosized particles formed by the reduction of palladium(II) phosphine complexes are either metallic nuclei stabilized by organophosphorus ligands or associates of polynuclear phosphido or phosphinideno palladium complexes whose surface contains immobilized Pd(0) clusters. The ensembles of the Pd(0) atoms are active in hydrogenation.     

Chirality induction of π-conjugated chains through chiral complexation

Chirality induction of π-conjugated polyanilines through chiral complexation with the chiral palladium(II) complexes was demonstrated to afford the chiral conjugated polymer complexes. Complexation of the emeraldine base of poly(o-toluidine) (POT) with the chiral palladium(II) complex bearing one labile coordination site led to the formation of the chiral conjugated polymer complex, which exhibited an induced circular dichroism (ICD) based on the chirality induction into a π-conjugated backbone. The mirror image of the CD signal was observed with the chiral conjugated polymer complex, which was obtained from the chiral palladium(II) complex possessing the opposite configuration. The chirality of the podand ligand moieties of the palladium complex is considered to induce a propeller twist of the π-conjugated molecular backbone. The crystal structure of the chiral conjugated complex of N-bis(4′-dimethylaminophenyl)-1,4-benzoquinonediimine (L³) as a model compound of the polyaniline revealed a chiral propeller twist conformation of the π-conjugated backbone. Furthermore, chiral complexation with the cationic palladium(II) complexes provided the ionic chiral conjugated complexes.     

二氧化硅负载聚-γ-(二苯胂基)丙基硅氧烷钯(0)配合物的合成与催化卤代芳烃的偶联反应

聚 γ 氯丙基硅氧烷依次与二苯胂钾、氯化钯作用 ,再经水合肼还原 ,合成了二氧化硅负载的聚 γ (二苯胂基 )丙基硅氧烷钯 (0 )配合物 .该钯 (0 )配合物可有效地催化芳基卤化物与烯烃、炔烃、Grignard试剂之间的交叉偶联反应 ,并且可以回收再用多次 ,其活性基本保持不变 .     

Novel trinuclear palladium(0) complexes; tris(tribenzylideneacetylacetone) tripalladium(solvent) complexes and their reactions

In an extension of our studies on palladium(0)dibenzylideneacetone complexes, novel trinuclear palladium complexes with three molecules of tribenzylideneacetylacetone have been obtained and identified by elemental and spectroscopic analyses (IR, UV and NMR).Ligand exchange reactions, oxidative addition reactions and complex formation reaction with maleic anhydride, dimethyl acetylenedicarboxylate and para-quinones were investigated. These were found to be similar to those of palladium (0)dibenzylideneacetone complexes.     

Transfer hydrogenation using recyclable polyurea-encapsulated palladium: efficient and chemoselective reduction of aryl ketones

A robust and recyclable palladium catalyst [Pd0EnCat] has been prepared by ligand exchange of polyurea-encapsulated palladium(II) acetate with formic acid, resulting in deposition of Pd(0) in the support material; Pd0EnCat is shown to be a highly efficient transfer hydrogenation catalyst for chemoselective reduction of a wide range of aryl ketones to benzyl alcohols.     

Preconcentration of palladium in a flow-through electrochemical cell for determination by graphite furnace atomic absorption spectrometry

An electrochemical preconcentration at a controlled potential on the electrode in a flow-through mode followed by graphite furnace atomic absorption spectrometric (GFAAS) detection is proposed for determination of trace amounts of palladium. After electrolysis the polarization of the electrodes was changed and deposited metal was dissolved electrochemically in the presence of an appropriate stripping reagent. Conditions for the electrodeposition, such as pH of the solutions, a deposition potential, dissolution potential and a composition of stripping solution were optimised. The graphite electrode (GE) and glassy carbon electrode (GCE) were tested for the palladium reduction process. The detection limit of 0.05 ng ml⁻¹ Pd (1 pg) was obtained after palladium preconcentration on the GCE and dissolution with 0.2 mol l⁻¹ thiourea in 0.1 mol l⁻¹ HCl followed by GFAAS detection. The method was applied for the determination of palladium in spiked tap water and road dust samples.