867 research outputs found
Birthday of Professor Andy Hor
No full textMetals are involved in various research fields of chemistry where they play key roles, as illustrated for example in transition-metal homogeneous catalysis, materials for energy storage and conversion, luminescent materials, and coordination-driven self-assembly. This special collection of Chemistry – An Asian Journal features significant contributions that chemists around the world make in this area. Working together with Professors Pierre Braunstein, Chi-Ming Che, Guo-Xin Jin, Fuwei Li and Yun Zong, Chemistry – An Asian Journal assembled 56 excellent contributions in this special collection to celebrate the 65th birthday of Prof. Andy Hor (A*STAR, Singapore).published_or_final_versio
The Author of the Hor-chos-ẖbyuṅ
No full textG. Huth, when translating the Hor-chos-ẖhbyuṅ (Geschichte des Buddhismus in der Mongolei, i, Strassburg, 1892), attributed this chronicle to ẖJigs-med nam-mkhaẖ, a high incarnate bLa-ma of the great bLa-bran bKra-śis-ẖkhyil monastery in the Amdo Province of North-Eastern Tibet. For over fifty years this attribution remained unchallenged, notwithstanding the fact that it is based on a wrong translation of the Tibetan text of the closing paragraphs of the chronicle. An attentive perusal of the Tibetan text shows that ẖJigs-med nam-mkhaẖ, whose short biography is given on p. 225 of the Tibetan text of the Hor-chos-ẖbyuṅ (ed. G. Huth), and on p. 356 of Huth's translation (Geschichte des Buddhismus in der Mongolei, ii, 1896), was not the author of the chronicle, but the inspirer of the work which was carried out at ẖJigs-med nam-mkhaẖ's command by Gu-śri (kuo-shih or State Preceptor) dKaẖ-bcu Su-dhī (Śuddhi) Ā-yu-warta (Āyurvarta), also known by the name of dbYaṅs-can sGeg-pahi blo-gros ẖJigsmed Rig-paẖi rdo-rje. The author of the chronicle met with ẖJigsmed nam-mkhaẖ during the latter's visit to the Barūn Türned principality in Eastern Mongolia (see Hor-chos-ẖbyuṅ, pp. 227–8). This ẖJigs-med nam-mkhah, better known by his title of Zam-tsha sku-zabs rin-po-che, was one of the “Four Golden Pillars” of bLa-bran in Amdo.1 Soon after A.D. 1803 (chu-phag lo, Water- Hog year) ẖJigs-med nam-mkhah was appointed to the abbot's chair (chos-khri) of the Yung Ho Kung () monastery in Peking. Later he was nominated tamaya lama (tha-ma-ka bla-ma) of Dolōn-nūr (mTsho-bdun) in Chakhar (E. Mongolia).</jats:p
Utilizing Benign Oxidants for Selective Aerobic Oxidations Using Heterogenized Platinum Nanoparticle Catalysts
No full textCopyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. By using platinum nanoparticle catalysts that are generated in situ by extrusion from a porous copper chlorophosphate framework, the role of oxidants in the selective oxidation of benzyl alcohol to benzaldehyde was evaluated, with a view to establishing structure-property relationships. With a detailed study of the kinetic properties of the oxidation reaction, it has been determined that the aerobic oxidation pathways progress with lower levels of product selectivity and higher activation energies (72.4-1) than the peroxide-based ones (23.6-1); affording valuable insights in the design of solid catalysts for selective oxidation reactions. Furthermore, through the use of X-ray absorption spectroscopy, the effect of calcination temperature on the degree of extrusion and its influence on nanoparticle formation have been evaluated, leading to the establishment of structure-activity correlations between the observed activation energies and the proportion of nanoparticle species generated. Tuned cats.: Well-defined platinum nanoparticles are generated in situ by anion extrusion within porous framework architectures (see figure). In these catalysts the local structural environment of the active site is controlled by the calcination conditions, and thus industrially significant, sustainable catalytic oxidation reactions are possible with tert-butyl hydroperoxide (TBHP) or oxygen.link_to_subscribed_fulltex
Substituted Metal Carbonyls XV. Crystal and Molecular Structures of Two Isomorphous Singly Diphosphine-Bridged Complexes(OC)5(mu-dppf)M(CO)5. CH2Cl2 (M = Cr, Mo;Dppf = (PPh2C5H4)2Fe)
No full textSynthesis and structural characterisation of the lead–platinum sulfido aggregates [Pt₂(μ-S)₂(PPh₃)₄PbX₂] (X = Br, I); promotion of rare tetrahedral geometry for lead(II)
No full textThe reactions of [Pt₂(μ-S)₂(PPh₃)₄] with excess PbBr₂ or PbI₂ in methanolic suspension result in the formation of the neutral lead(II) halide adducts [Pt₂(μ-S)₂(PPh₃)₄PbX₂] (X = Br, I). The X-ray structure determination of the lead iodide adduct reveals an essentially tetrahedral lead(II) centre, which is a rare coordination geometry for lead(II), which almost invariably is hemidirected, with a stereochemically active lone pair. In contrast, the structure of the PbBr2 adduct, although suffering from some disorder, shows a more typical, distorted arrangement of ligands; these results are discussed in terms of the tendency for soft, bulky ligands to promote symmetric, holodirected geometries. The ESI mass spectra of the adducts are reported, and yield [M−halide]⁺ ions
Dinuclear platinum(II) sulfide–thiolate complexes [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ containing fluorinated substituents and the identification of a SC₆F₅ π interaction in the crystal structure of [Pt₂(μ-S)(μ-SCH₂C₆F₅)(PPh₃)₄]BPh₄•2C₆H₆
No full textReactions of the platinum(II) sulfido complex [Pt₂(μ-S)₂(PPh₃)₄] with the alkyl iodides ICH₂CH₂(CF₂)nCF₃ (n = 3, 7) gives good yields of the monoalkylated products [Pt₂(μ-S){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]⁺, which were isolated as PF₆⁺or BPH₄⁻ salts, and characterised by ESI mass spectrometry, NMR spectroscopy and elemental analysis. The complex [Pt₂(μ-S){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]⁺ appears to have normal reactivity for this type of complex, namely reaction with Ph₃PAuCl to give [Pt₂(μ-SAuPPh₃){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]₂⁺, and reaction with Me₂SO₄ to give [Pt₂(μ-SMe){μ-SCH₂CH₂(CF₂)nCF₃}(PPh₃)₄]₂⁺. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with C₆F₅CH₂Br gave [Pt₂(μ-S)(μ-SCH₂C₆F₅)(PPh₃)₄]⁺, isolated as BPh₄⁻ its salt, and characterised by NMR spectroscopy and a single-crystal X-ray structure determination. The C₆F₅ group lies above the {Pt₂S₂} core of the complex as a result of a SC₆F₅ π interaction, in contrast to the published structure of [Pt₂(μ-S)(μ-SCH₂C₆H₅)(PPh₃)₄]PF₆, where the C₆H₅ group projects away from the {Pt₂S₂} core
Probing the origin of in situ generated nanoparticles as sustainable oxidation catalysts
No full textA novel method for the in situ generation of catalytically active small metal nanoparticles, by anion extrusion on a parent porous copper chloropyrophosphate framework, has been developed to generate gold, platinum and palladium nanoparticles for sustainable catalytic oxidations using molecular oxygen as the oxidant. Transmission electron microscopy coupled with detailed structural and physico-chemical characterisation, in combination with in-depth kinetic analysis have afforded profound insights into the nature of the active site for facilitating structure–property correlations
Synthesis and characterisation of adducts of [Pt₂(μ-S) ₂(PPh₃)₄] with organo-palladium and platinum-hydride substrates
No full textThe reactions of [Pt₂(μ-S) ₂(PPh₃)₄] towards a range of palladium(II) complexes containing organometallic ligands (cyclopalladated N-donor ligands, η³-allyl, phenyl) have been explored, leading to the formation of a series of cationic, trinuclear sulfido-bridged aggregates containing {Pt₂PdS₂} cores. [Pt₂(μ-S) ₂(PPh₃)₄] also reacts with the platinum(II) hydride complex trans-[PtHCl(PPh3)₂] giving the adduct [Pt₂(μ-S) ₂ (PPh₃)₄PtH(PPh₃)]+. X-ray crystal structure determinations on the complexes [Pt2(μ-S) ₂ (PPh₃)₄PdPh(PPh₃)]PF₆ and [Pt₂ (μ-S) ₂ (PPh₃)₄PtH(PPh₃)]PF₆ are reported, and show the expected bis μ₃-sulfido aggregates with three square-planar metal centres
Dinuclear sulfide–thiolate complexes [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ as cationic metalloligands
No full textThe cationic monoalkylated derivatives of the well-known metalloligand [Pt₂(μ-S)₂(PPh₃)₄], viz. [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ (R = n-Bu, CH₂Ph) are themselves able to act as metalloligands towards the Ph₃PAu⁺ and R′Hg⁺ (R′ = Ph or ferrocenyl) fragments, by reaction with Ph₃PAuCl or R′HgCl, respectively. The resulting dicationic products [Pt₂(μ-SR)(μ-SAuPPh₃)(PPh₃)₄]²⁺ and [Pt₂(μ-SR)(μ-SHgR′)(PPh₃)₄]²⁺ are readily isolated as their hexafluorophosphate salts, and have been fully characterised by spectroscopic techniques and an X-ray structure determination on [Pt₂(μ-SR)(μ-SHgFc)(PPh₃)₄](PF₆)₂
Thallium(III) complexes of the metalloligands [Pt₂(μ-S)₂(PPh₃)₄] and [Pt₂(μ-Se)₂(PPh₃)₄]
No full textReactions of [Pt₂(μ-S)₂(PPh₃)₄] with the diarylthallium(III) bromides Ar₂TlBr [Ar = Ph and p-ClC₆H₄] in methanol gave good yields of the thallium(III) adducts [Pt₂(μ-S)₂(PPh₃)4TlAr₂]⁺, isolated as their BPh₄⁻ salts. The corresponding selenide complex [Pt₂(μ-Se)₂(PPh₃)₄TlPh₂]BPh₄ was similarly synthesised from [Pt₂(μ-Se)₂(PPh₃)₄], Ph₂TlBr and NaBPh₄. The reaction of [Pt₂(μ-S)₂(PPh₃)₄] with PhTlBr₂ gave [Pt₂(μ-S)₂(PPh₃)₄TlBrPh]⁺, while reaction with TlBr₃ gave the dibromothallium(III) adduct [Pt₂(μ-S)₂(PPh₃)₄TlBr₂]⁺[TlBr₄]⁻. The latter complex is a rare example of a thallium(III) dihalide complex stabilised solely by sulfur donor ligands. X-ray crystal structure determinations on the complexes [Pt₂(μ-S)₂(PPh₃)₄TlPh₂]BPh₄, [Pt₂(μ-S)₂(PPh₃)₄TlBrPh]BPh₄ and [Pt₂(μ-S)₂(PPh₃)₄TlBr₂][TlBr₄] reveal a greater interaction between the thallium(III) centre and the two sulfide ligands on stepwise replacement of Ph by Br, as indicated by shorter Tl-S and Pt...Tl distances, and an increasing S-Tl-S bond angle. Investigations of the ESI MS fragmentation behaviour of the thallium(III) complexes are reported
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