Dissolution of gold in the DMSO—RX systems. The concept of a donor-acceptor electron transport system

Summary The liquid phase oxidation of gold in donor-acceptor organic and aqueous-organic media has been studied. The compounds [AuCl(Me₂S)], [AuBr(Me₂S)], [AuBr₃(Me₂S)], [Me₃S][AuBr₄], [Me₃S][AuBr₄(Me₂S)]·H₂O, [Me₃SO]-[AuBr₄]·H₂O, [Me₃S][Au₂Br₇(Me₂S)₂]·3H₂O, [Me₃S]₂-[Au₂Br₈]·2DMSO·H₂O, [Me₂(Bu)SO][AuBr₄]·H₂O and [Me₃S]Br were isolated by dissolution of Au⁰ in DMSO-RX mixtures (R = H or Bu; X = Cl or Br). The products were characterized by elemental analysis and i.r. spectroscopy. The nature of the Au⁰-DMSO-RX systems and the oxidant species are discussed in terms of a newly-developed concept of donor-acceptor electron transport (DAET) systems.     

AuBr3-catalyzed cyclization of o-(alkynyl)nitrobenzenes. Efficient synthesis of isatogens and anthranils

The cyclization of o-(arylalkynyl)nitrobenzenes was catalyzed by AuBr₃ to produce the corresponding isatogens in good to high yields together with small amounts of anthranils. On the other hand, anthranils were obtained selectively when the AuBr₃-catalyzed reaction was carried out using o-(alkylalkynyl)nitrobenzenes.     

Propargyl 1,2-orthoesters as glycosyl donors: stereoselective synthesis of 1,2-trans glycosides and disaccharides

Propargyl 1,2-orthoesters are identified as glycosyl donors. Various glycosides and disaccharides were synthesized in a stereoselective manner using AuBr₃ as the promoter. AuBr₃ may activate the alkyne resulting in the formation of a 1,2-dioxolenium ion and also behaves as a Lewis acid to facilitate the attack of the glycosyl acceptor. The versatility of the protocol was demonstrated using a panel of aglycones comprising aliphatic, alicyclic, steroidal and sugar alcohols.     

Die Pyridinaddukte der Goldhalogenide. 3. Darstellung,Eigenschaften und Kristallstruktur zweier Modifikationen von AuBr · NC5H5

Pyridine Adducts of Gold Halides. 3. Preparation, Properties, and Crystal Structure of Two Modifications of AuBr · NC₅H₅ The reaction of AuBr · S(CH₂C₆H₅)₂ with pyridine in absolute ethanol yields the crystalline compound AuBr · pyridine. It crystallizes in the triclinic space group P1 with the lattice constants a = 791.5(2) pm, b = 935.6(2) pm, c = 1005.1(3) pm, α = 85.78(2)°, β = 102.07(2)°, γ = 109.31(2)°. When the solvent is toluene, monoclinic crystals are formed with the space group C2/c and a = 1225.9(2) pm, b = 1522.2(3) pm, c = 1459.7(3) pm, β = 97.82(2)°. The triclinic structure is built up by Au₄ zig-zag chains AuBr₂—Au(py)₂—Au(py)₂—AuBr₂, whereas the monoclinic phase contains infinite chains with the sequence AuBr₂—Au(py)₂. In each case the linkage is formed by weak Au—Au-interactions.     

Synthesis,spectroscopic characterization,crystal structure determination and DFT calculations of [Au(Me<Subscript>2</Subscript>phen)Br<Subscript>2</Subscript>][AuBr<Subscript>2</Subscript>]

New mixed valence gold(III/I) salt containing two complexes [Au(Me₂phen)Br₂][AuBr₂] (1) was prepared from the reaction of AuBr₃ and 5,6-dimethyl-1,10-phenanthroline (Me₂phen) in a mixture of methanol and acetonitrile. Suitable crystals of 1 for X-ray diffraction measurement were obtained by slow evaporation of the resulted red solution at room temperature. This complex was characterized by spectral methods (IR, UV–Vis and ¹H NMR), elemental analysis and single-crystal X-ray diffraction. The X-ray structural analysis indicated that the asymmetric unit of 1 contains one [Au(Me₂phen)Br₂]⁺ cation and two half anions of [AuBr₂]^ˉ. Furthermore, the packing diagram of this complex, 3-D structure stabilized by intermolecular Au…Br and Au…π interactions and intermolecular C–H···Br hydrogen bonds. The experimental investigations on complex have been accompanied computationally by the density functional theory (DFT) and time-dependent DFT calculations. The nature of the Au–N bonds was investigated using quantum theory of atoms in molecules. Moreover, natural bond orbital analysis carried out to obtain hyper-conjugative interactions and electron delocalization on the complex.     

AuBr3-Catalyzed Chemoselective Annulation of Isocyanates with 2H-Azirine

The chemoselective cyclization of isocyanates with 2H-azirine was achieved with AuBr₃ as catalyst. This transfer sets the stage for the synthesis of aromatic oxazole-ureas in a tandem process. The addition of a catalytic amount of phosphite enhances the process enormously. The reaction can also be performed in a one-pot process using benzoyl azide instead of isocyanate under the same conditions. A detailed study on the role of the phosphite that was applied as an additive revealed that only non-coordinated phosphite can reduce gold(III) and that gold(I) coordinated phosphite is not oxidized. Accompanied by the reduction of gold, HBr is generated in situ, which turned out to be the actual promotor in combination with the remaining AuBr₃. The positive effect of acid can be explained by a strong N–Au coordination, which tends to break more easily in the presence of small amount of protic acid in the reaction solution.     

Investigation of thermal properties of double complex salts [M(NH3)5Br][AuBr4]2·nH2O, M?=?Rh, Ir

Novel double complex salts [M(NH₃)₅Br][AuBr₄]₂·nH₂O, M?=?Rh, Ir, have been synthesized and examined. The processes of thermal decomposition of the compounds in inert and reductive atmospheres have been studied and intermediate products identified. Simultaneous thermal analysis with parallel mass-spectrometric analysis of evolved gases (STA-EGA) has been employed for identification of main gaseous products of thermolysis in inert atmosphere. It has been revealed that the final products of decomposition in inert or reductive atmospheres are fine powders of gold and the corresponding platinum metal with sizes of crystallites 4?C40?nm. The possibility of preparation of the metastable solid solution Au_0.05Ir_0.95 on thermolysis of [Ir(NH₃)₅Br][AuBr₄]₂·H₂O in inert atmosphere has been demonstrated.     

Gold-catalyzed regiospecific intermolecular hydrothiolation of allenes

AuBr₃-catalyzed regiospecific intermolecular hydrothiolation of aromatic allenes and aromatic thiols afforded the corresponding dithioacetals in good yields at 0 °C in 5 min.     

Die analytische Anwendung von Polymethylenammoniumsalzen

Zusammenfassung Die gravimetrische Halbmikrobestimmung von Gold als Bis(trimethyl)-hexamethylendiammonium-tetrabromo-aurat(III) [(CH₃)₃N-(CH₂)₆N(CH₃)₃][AuBr₄]₂ ermöglicht bei durchschnittlichen Minusbefunden von 0,6% seine Trennung von größeren Überschüssen der Ionen: Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺.

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Summary The gravimetric semi-micro determination of gold as bis(trimethyl)-hexamethylenediammonium-tetrabromoaurate(III), [(CH₃)₃N(CH₂)₆-N(CH₃)₃][AuBr₄]₂, is described. A separation of gold froma larger excess of the ions Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺ and Cu²⁺ can be achieved by this method. The average minus error is 0.6%.

     

Synthesis of Thioglycosides from Propargyl Glycosides Exploiting Alkynophilic Gold Catalyst

Various thioglycosides were synthesized from stable propargyl glycosides using catalytic quantity of AuBr₃ and various thiol aglycons. The current protocol enables preparation of thioglycosides from propargyl glycosides in an efficient and simple manner. The reaction is fast, catalytic, and mild. Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Carbohydrate Chemistry to view the free supplemental file.     

Extraktiv-photometrische Bestimmung von Gold als Hydrogen-tetrabromo-bis-(Pyridin-N-0 xid)aurat(III)

Zusammenfassung Durch Separierung von Gold als H[AuBr₄(ONC₅H₅)₂] können 10 bis 120g Au³+ neben 2 · 10⁴fachen Überschüssen an Kupfer u. a. Metallionen extraktiv-photometrisch bestimmt werden. Über die Bindungsverhältnisse der Liganden in Hydrogen-tetrahalogen-bis-(Pyridin-N-Oxid)auraten(III) liegen IR- und KMR-Untersuchungen vor.

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Extractive-photometric determination of gold as hydrogen-tetrabromo-bis-(pyridine-N-oxide)aurate(III)

Summary By separating the gold as H[AuBr₄(ONC₅H₅)₂] it is possible to determine 10 to 120g Au³⁺ by extractive-photometric means in the presence of 2 · 10⁴ excess of copper and other metal ions. Studies have been made also of the combining relationships of the ligands in hydrogen-tetrahalogeno-bis-(pyridine-N-oxide)aurates(III) employing IR- and NMR-investigations.

     

Mikrogravimetrische Bestimmung von Gold als Dekamethonium-Tetrabromoaurat(III)

Zusammenfassung Die mikrogravimetrische Bestimmung von Gold als Bis(trimethyl)-dekamethylendiammoniumtetrabromoaurat(III) [(CH₃)₃N-(CH₂)₁₀-N(CH₃)₃] [AuBr₄]₂ erlaubt die Erfassung von 700g Au neben 200fachen Überschüssen an Cu²⁺ und Ni²⁺ sowie 50fachen Mengen anderer Übergangsmetalle.

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Summary The microgravimetric determination of gold as bis-(trimethyl) decamethylenediammoniumtetrabromaurate(III) [(CH₃)₃N-(CH₂)₁₀-N(CH₃)₃] [AuBr₄]₂ permits the determination of 700g Au in the presence of 200-fold excesses of Cu²⁺ and Ni²⁺ as well as 50-fold amounts of other transition metals.

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Résumé Le microdosage gravimétrique de l'or à l'état de tétrabromoaurate-III de bis(triméthyl)décaméthylènediammonium [(CH₃)₃N-(CH₂)₁₀-N(CH₃)₃] [AuBr₄]₂ permet de descendre jusqu'à 700g Au en présence d'un excès de 200 fois Cu²⁺ et Ni²⁺ et d'une quantité 50 fois plus grande des autres métaux de transition.

     

The roles of ligands proton affinity, π-back donation and metal fragment hardness on the Au–N bond in N-donor heterocycles gold(III) complexes

A DFT study on the Au–N interaction for some groups of N-donor heterocycles L {L = pyridines (py), pyrimidines (pm), imidazoles (im), pyrazoles (pz) and isoxazoles (io)} in neutral AuX₃L complexes {AuX₃ = AuBr₃, AuCl₃, trans-AuCl(CN)₂, Au(CN)₃} is reported. Linear relationships between the AuX₃ Mulliken charge in AuX₃L and the computed proton affinity (PA) of the heterocycle were found for all the considered ligands. The different slopes found on changing the N-donor species represent a measure of the π-acidity of these nitrogen ligands once coordinated to the metal centre, by the consequence a π-acceptor ability scale has been derived. The π-acceptor ability of the 5-membered N-donor ligands resulted in all the cases greater than that of the 6-membered N-heterocycles. The proton affinity average value corresponding to a zero charge of the AuX₃ and L fragments in the AuX₃L species has been estimated. This parameter represents the minimum PA value for the formation of a bond between the N-heterocycles and gold(III) and it does not depend on the electronic features of the coordinated ligands. The sensitivity of the AuX₃ fragments towards ligands PA variations follows the order Au(CN)₃ < trans-AuCl(CN)₂ < AuCl₃ < AuBr₃ and this last result has been explained on the basis of the metal fragments relative hardness.     

Gold-catalyzed glycosidations: synthesis of 1,6-anhydro saccharides

Various 1,6-anhydro sugars are synthesized utilizing salient features of gold-catalyzed glycosidations. All the reactions occurred under mild conditions in the presence of 7 mol % of AuBr₃ enabling easy synthesis of 1,6-anhydro sugars from corresponding 6-hydroxy propargyl/methyl monosaccharides, disaccharides, and trisaccharides in good yields.     

79,81Br NQR Spectra of bromochalcogenide complexes of Au(III), Pt(IV), and Pd(II)

Conclusions The structure of bromochalcogenide complexes of gold, platinum, and palladium, viz., AuBr₄· SeBr₃, PtBr₆(SeBr₃)₂, PtBr₆(TeBr₃)₂, and PdBr₂(SeBr₂)₂, has been established with the aid of the NQR spectra of the bromine atoms. In the compounds of gold and platinum investi gated SeBr₃ groupings are coordinated as ligands, and in the palladium complex SeBr₂ groupings serve as ligands.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1545–1548, July, 1986.     

Oxidation of transition metals in the liquid phase. 9. Direct synthesis and X-ray structural examination of complexes [(Me2S)AuBr] and [(Me2S)AuBr3]

Conclusions Oxidation of Au₀ in the DMSO-HBr system has given dimethyl sulfide complexes of mono-and trivalent gold, [(Me₂S)AuBr] and [(Me₂S)AuBr₃]. X-ray diffraction examination has shown that in the crystal of the first complex there are chain intermolecular contacts Au...Au (3.22 å), and in the crystal of the second, intermolecular Au...Br contacts which extend the square planar coordination of the gold atoms to distorted bipyramidal.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 450–455, February, 1988.     

Crystal structures of new double complex salts [M(NH3)5Br][AuBr4]2·H2O, where M = Ir, Rh and complex salt [Ir(NH3)5Br]Br2

The crystal structures of double complex salts [M(NH₃)₅Br][AuBr₄]₂·H₂O (M = Ir, Rh) are determined by single crystal XRD. The compounds crystallize in the triclinic system, P-1 space group, Z = 4. Crystallographic characteristics: [Ir(NH₃)₅Br][AuBr₄]₂·H₂O: a = 8.2982(3) ?, b = 15.3045(4) ?, c = 17.4378(6) ?, α = 73.064(1)°, β = 88.938(1)°, γ = 86.221(1)°, V = 2113.95(12) ?³, d _x = 4.419 g/cm³, R = 0.0469; [Rh(NH₃)₅Br][AuBr₄]₂·H₂O: a = 8.2855(2) ?, b = 15.2881(3) ?, c = 17.4053(4) ?, α = 73.015(1)°, β = 88.913(1)°, γ = 86.267(1)°, V = 2104.08(8) ?³, d _x = 4.165 g/sm³, R = 0.0480. The crystal structure of [Ir(NH₃)₅Br]Br₂ is determined. The compound crystallizes in the orthorhombic system, Pnma space group, Z = 4. Crystallographic characteristics: a = 13.8521(3) ?, b = 10.8570(2) ?, c = 6.9908(1) ?, V = 1049.31(3) ?³, d _x = 3.273 g/cm³, R = 0.0127.     

Two‐Dimensional Networks of [AuCl4]– and [AuBr4]– Anions

Several salts of protonated amines and aza‐aromatics with [AuCl₄]^– and [AuBr₄]^– anions contain two‐dimensional (“square”) anionic networks that display short halogen ··· halogen contacts. The Au₄ quadrilaterals formed by neighboring anions of the networks are to a good approximation squares, with sides of around 7.5 Å for tetrachloridoaurates and 8 Å for tetrabromidoaurates.     

Synthesis of Modified Di- and Trisaccharide Fragments of N-Glycoproteins

Abstract

The syntheses of several analogues of disaccharide Manot(1→6)Mana-OCH₃ (1) and of trisaccharide Mana(1→6)[Mana(1→3)]Mana-OCH₃ (2) are reported. The syntheses are described of the diastereomeric 6-methyl derivatives 9a and 9b, which are representatives of fixed conformations of disaccharide 1. The syntheses of the 2-amino-2-deoxy analogues 15 and 17 and the synthesis of the 2-fluoro-2-deoxy analogue 28 are also reported.     

Secondary interactions in the crystal structure of heterovalent 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III) dibromoaurite(I)

The complex [Au(C₁₄H₂₂N₄)][AuBr₂] with two types of gold atoms (Au(III) and Au(I)) was obtained. In the cation 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III), the Au atom is coordinated by four N atoms of the tetraazamacrocyclic amide ligand to make up a distorted square. The dibromoaurite(I) anion is linear. The conformation and packing of the structure is determined and stabilized by weak intermolecular hydrogen bonds C-H…Br and C-H…Au, an aurophilic interaction Au(I)…Au(III), and coordination bonds Au…N.