AuBr Research Articles

Studies on gold(II) complexes with hard and soft donor ligands. Part IV. A reactivity study in solution using EPR spectroscopy

The reactions of Au(II) complexes, cis-[Au(mta)2Cl]Cl (1a), trans-[Au(mta)2Cl]Cl (1b), [Au(mta)2Cl]2Cl2 (1c), Au(pma)Cl (2a), Au(pma)Br (2b) and Au2(pma)Cl4 (2c), where mta and pma are the deprotonated ligands of o-methylthioaniline (Hmta) and N-(2-pyridylmethyl)-2-mercaptoaniline (Hpma), respectively, are reported. When these complexes are reacted with selected ligands containing nitrogen donors, the resulting EPR spectra are indicative of coordination with the nitrogen of the incoming ligand. Both compounds 2a and 2c react with cysteine (cys) in DMF solution to produce the stable reaction product [Au(pma)(cys)]2 (2e), the EPR spectrum of which indicates the presence of two interacting gold(II) ions to form a dimeric system. A radical formed during the course of the reaction of 2c with CN− in DMSO solution which exhibits a multiline EPR spectrum with a g value of 2.003 may be due to the formation of pyridine-N-oxide anion radical subsequently stabilized by either DMSO complex formation and/or σ-bond formation to the central metal atom.

(2-Methylphenyl)phosphin]gold(I)-bromid: Eine neue Strukturvariante für intermolekulare Au ··· Au-Kontakte bei (Phosphan)gold(I)-halogeniden / [(2-Methylphenyl)phosphine]gold(I) Bromide: A New Type of Structure for Au ··· Au Contacts in (Phosphine)gold(I) Halides

(2-Methylphenylphosphine)gold(I) bromide has been prepared from tetrabutylammonium dibromoaurate(I) and the primary phosphine in almost quantitative yield. The structure of the compound has been determined by single crystal X-ray diffraction (space group C2/c, Z = 8). The monomer units (2-MeC6H4PH2)AuBr with an almost linear P—Au—Br axis are aggregated in the solid through short Au ··· Au contacts to give folded chains of gold atoms with alternating Au · · · Au distances of 3.097(1) and 3.380(1) A, respectively, a repetitive angle AuAuAu of 103.5(1)°, and alternating dihedral angles AuAuAuAu of 180 and ± 104.5°, respectively. The monomers in adjacent dimers (RPH2AuBr)2 are related crystallographically by a center of inversion or by a two-fold axis, respectively.

Reduction reactions of gold(III) bromocomplexes in dimethyl sulfoxide

The reactions of AuBr 4 − with uracil and uridine in dimethyl sulfoxide (Me 2SO) lead to the reduction of gold(III) to gold(I) and to the formation of the corresponding 5-bromopyrimidine. In Me 2SO containing water the 5-bromo-6-hydroxy-5,6-dihydro-pyrimidine is also formed. The observed redox kinetics are consistent with a mechanism involving reductive elimination of bromine from the gold(III) complex followed by halogenation of the pyrimidine. The specific rates for the reduction of AuBr 4 − with both pyrimidines in Me 2SO and in the partially aqueous solvent are greater than those for the corresponding reactions in water, uracil being more reactive than uridine. The tetrabromoaurate(III) ion is also reduced by Me 2SO. The triphenylphosphine complex Au(PPh 3)Br 3 reacts with uridine in Me 2SO to give 5-bromouridine. Reduction of gold(III) to gold(I) also occurs through a reaction involving the formation of triphenylphosphine oxide.

Reaction products between gold(III) bromide and tetramethylthiourea: dibromobis(tetramethylthiourea)gold(III) dibromoaurate(I) and bromo(tetramethylthiourea)gold(I). Synthesis, crystal and molecular structure, and infrared spectra

The compounds dibromobis(tetramethylthiourea)gold(III) dibromoaurate(I), [Au(tmtu)2Br2][AuBr2], and bromo(tetramethylthiourea)gold(I), [Au(tmtu)Br] were prepared and characterized by means of X-ray diffraction. The crystals of [Au(tmtu)2Br2][AuBr2] are triclinic, space group P, (Ci1, no. 2) with a= 8.223(1), b= 9.987(1), c= 8.078(1)A, α= 105.74(1), β= 117.20(1), γ= 84.35(1)°, and Z= 2; the crystals of [Au(tmtu)Br] are monoclinic, space group P21/c, (C2h5, no. 14) with a= 6.999(1), b= 19.898(1), c= 8.044(1)A, β= 115.75(1)°, and Z= 4. The structures were solved by the heavy-atom method, and least-squares refinement of structural parameters led to a conventional R factor of 0.034 (R′= 0.034) for 1 677 and R= 0.028 (R′= 0.029) for 1 271 independent reflections for [Au(tmtu)2Br2][AuBr2] and [Au(tmtu)Br] respectively. The compound [Au(tmtu)2Br2][AuBr2] is ionic. The structure consists of centrosymmetric units in which the two gold atoms are four- and two-co-ordinated, respectively. The ligand is trans-co-ordinated to the gold (III) of the cationic part of the compound, together with two bromine atoms forming a square-planar geometry; the anionic part is formed by linearly co-ordinate dibromoaurate(I). The structure of [Au(tmtu)Br] consists of two-co-ordinated gold(I) units. Each tetramethylthiourea is bonded by the sulphur atom. Infrared bands are diagnostic of the co-ordination environments around the metal atoms.

Gold(I) complexes of thio- and dithiocarbamate esters. The structure of bis(N-methyl-O-ethyl-thiocarbamate)gold(I) chloride

The complexes Au(TMDT)Br, Au(TMDT)Cl, [Au(PPh 3)(TMDT)]NO 3 and Au(MTC) 2Cl (TMDT = N,N-dimethyl- S-methyl-dithiocarbamate, MTC = N-methyl- O-ethyl-thiocarbamate) have been prepared and characterized. The crystal structure of Au(MTC) 2Cl was determined by X-ray crystallography and refined to R = 0.035 based on 2654 observed reflections. The compound is triclinic, space group P 1 , with a = 6.937(6), b = 9.439(5), c = 12.286(4) Å, α = 74.16(3), β = 99.54(3), γ = 108.06(3)°. The structure consists of Au(MTC) 2 + cations significantly distorted from the linear coordination, with a SAuS angle of 155.3(1)° and AuS bond distances of 2.286(2) and 2.284(2) Å, and uncoordinated Cl − anions hydrogen bonded to the two MTC ligands in each cation, with NH···Cl distances of 3.04(1) Å. 1H NMR spectra of the dithiocarbamate complexes are consistent with coordination of the ligand through its thiocarbonyl sulfur atom.

The Crystal Structure of the Gold(III) Complex, Tribromo(dibenzyl sulfide)gold(III)

Abstract The crystal structure of tribromo(dibenzyl sulfide) gold(III) has been determined. The crystal belongs to the triclinic system, with a=7.002(1), b=7.949(1), c=17.244(2) Å, α=88.83(1), β=79.52(1), and γ=66.35(1)°, with the space group P\bar1 and with Z=2. The complex has a square-planar coordination geometry with 3BrlS donor atoms. The bond lengths of the three Au–Br coordinations are in the range of 2.41–2.43 Å.

The first example of a gold bis(diphenylphosphino)methane cationic dimer with a bridging iodide. The X-ray crystal structures of (μ-I)[Au(dppm)] 2[I] and [Au(dppm)Br] 2

(μ-I)[Au(dppm)] 2 [I] cristallise dans le systeme orthorhombique avec le groupe d'espace P2 1 2 1 2 1 . [Au(dppm)Br] 2 cristallise dans le systeme triclinique avec le groupe d'espace P1. Affinement de la structure jusqu'a 0,0425 et 0,0535 respectivement

Studies of intermolecular interactions in transition metal complexes—VI[1]: The electrical properties of some quasi-one dimensional mixed valence complexes at ultra-high pressures

Electrical conductivity and conductivity activation energy measurements were carried out on the quasi-one dimensional (1-D) mixed valence complexes, Pd(NH 3) 2Br 3 and Au(DBS)X 2 (DBS = dibenzylsulfide, X = Cl, Br), at pressures up to 360 Kbar using a diamond compact-tipped Drickamer apparatus. The results indicate an enormous enhancement of the conductivity with values approaching 5 Ω −1 cm −1 for the palladium complex and 2 × 10 −3 Ω −1 cm −1 for Au(DBS)Br 2 in the range 100–250 Kbar pressure. The increase in conductivity and decrease in the activation energy is attributed to compression along the 1-D chains, leading to more nearly equivalent coordination environments for the intrachain metal atoms. A maximum in the conductivity and a minimum in the activation energy is observed for these complexes, indicating that the pressure induced reduction in metal site inequivalency reaches a limit and that conversion to the hypothetical uniform-valence (Pd(III) or Au(II)), 1-D metallic state is not attained at high pressures. These observations are discussed in the context of the interatomic distances changes anticipated at high pressure.

ChemInform Abstract: SYNTHESIS, STRUCTURE, AND PROPERTIES OF TRICHLORO‐ AND TRIBROMO‐(2,9‐DIMETHYL‐1,10‐PHENANTHROLINE)GOLD(III)

AbstractDie diamagnetischen, quadratisch‐pyralnidalen Titelverbindungen (I) werden durch Umsetzung von K‐tetrachloroaurat?ll) mit dem N‐Liganden in Methanol/Benzol ohne bzw. in Gegenwart von Ammoniumbromid dargestellt und durch magnetische Suszeptibilitäts‐ und elektrische Leitfähigkeitsdaten charakterisiert.

Synthesis, structure, and properties of trichloro- and tribromo-(2,9-dimethyl-1,10-phenanthroline)gold(III)

The title complexes [(4) Au(dmp)Cl3 and (5) Au(dmp)Br3, dmp = 2,9-dimethyl-1,10-phenanthroline] have been synthesised and their crystal and molecular structures determined from three-dimensional X-ray data obtained by counter methods. Crystals of (4) and (5) are not isomorphous though both are monoclinic, space group P21/C, with Z= 4 in unit cells of dimensions: (4)a= 7.343(1), b= 18.712(3), c= 12.143(3)A, β= 112.29(2)°;(5), a= 8.046(1), b= 10.478(3), c= 20.079(5)A, β= 92.65(2)°. The structures were solved by the heavy-atom method and refined by full-matrix least-squares to R 0.035 [(4) 904 reflections] and 0.060 [(5) 1122 reflections].The compounds consist of discrete, diamagnetic five-co-ordinate molecules in both the solid state and in solution in aprotic solvents. The distribution of the ligands about the metal is approximately square pyramidal with the axial ligand displaced from the vertical, and at a relatively great distance from the metal, so that they may also be described as strongly distorted square planar. The direction of the distortion is such as to reduce the energy of the high-spin (triplet) state, but the magnitude is too low to produce a high-spin ground-state.

An X-Ray Investigation of the Structures of the Tetrachloro- and Tetrabromoaurate(III) Ions in Aqueous Solution

Abstract The structures of the AuCl4− and the AuBr4− complexes in aqueous solutions have been determined from X-ray scattering measurements on concentrated solutions of tetrachloroauric and tetrabromoauric acids. Both the tetrachloroaurate(III) and the tetrabromoaurate(III) complexes were found to have a square planar symmetry. The values obtained for the interatomic distances within the complexes are: Au–Cl, 2.291 Å; cis-Cl–Cl, 3.24 Å; trans-Cl–Cl, 4.58 Å; Au–Br, 2.432 Å; cis-Br–Br, 3.44 Å; trans-Br–Br, 4.86 Å.

Nuclear quadrupole resonance of halogens in tetrahaloaurates(III)

The nuclear quadrupole resonance of halogens in a variety of anhydrous and hydrated tetrahaloaurates(III) was observed between 77 and 400°K. From the number of resonance lines, the number of different kinds of crystallographically nonequivalent halogen atoms was determined. The ionic character of AuCl and AuBr bonds is estimated as 41% and 34%, respectively. The central gold atom in the tetracoordinated complex ion carries a fraction of protonic charge (0.64ϵ in [AuCI 4] − and 0.36ϵ in [AuBr 4] −, respectively). The positive temperature coefficient of resonance frequencies observed for some tetrahaloaurates(III) is attributable to hydrogen bond formation. The anomalous temperature dependence of bromine resonance frequency of cesium tetrabromoaurate(III) is presumed to be due to the torsional oscillation of tetrabromoaurate(III) ions in crystals involving a considerable anharmonicity.

Far-infrared spectra of four-co-ordinate planar gold(III) complexes

A Series of gold(III) complexes of the type [Au(L)X3](L = thioethers, triphenylphosphine, or triphenylarsine; X = Cl or Br) and trans-[Au(CN)2(L)X](L = pyridine or [2H5]pyridine; X = Cl or Br) have been prepared and their i.r. spectra as Nujol mulls have been recorded in the region 500–70 cm–1. For complexes [Au(L)X3], the metal–halogen stretching vibrations are assigned and discussed on the basis of the different trans-influence of the ligand L. For the complexes trans-[Au(CN)2(L)X], the gold–halogen and gold–carbon stretching vibrations are assigned and compared with the corresponding vibrations in the parent ions [Au(CN)4]– and trans-[Au(CN)2X2]–. The ν(Au–Cl) and ν(Au–Br) values for ligands trans to pyridine, are in the ranges 368–363 and 262–250 cm–1.

Presence of glucosaminidase activity in human synovial fluid and its inhibition by gold compounds

Abstract Human synovial fluid, obtained post mortem from knee joints, has been found to hydrolyse p -nitrophenyl-N-acetyl-β- d -glucosaminide to p -nitrophenol and N-acetyl glucosamine. The activity was measured at 37° and pH 4.5. Sodium aurothiomalate (“Myocrisin”) non-competitively inhibits this glucosaminidase activity. Gold tribromide and p -chloromercuribenzoate also inhibit the glucosaminidase activity. Inhibition by “Myocrisin” was observed at concentrations within the range that might be reached in the treatment of rheumatoid arthritis.

Further Clinical Observations on the Treatment of Pertussis with Gold Tribromide

Heroin-assisted treatment comprises the use of diacetylmorphine (pharmaceutical heroin) for individuals with severe opioid use disorder. In Switzerland, take-home doses in heroin-assisted treatment are more strictly regulated as compared to conventional opioid agonist treatment. In light of the COVID-19 pandemic, the Swiss Federal Council provisionally adapted its policy, allowing for longer prescriptions of take-home diacetylmorphine. Before the beginning of the pandemic, take-home doses only occurred in exceptional circumstances and under strict criteria for patient eligibility. Following the legislative adaptations, we critically revised our internal centre policies as well. We report our experiences with oral take-home diacetylmorphine from a Swiss outpatient university centre specialising in heroin-assisted treatment. An additional 45 patients received take-home doses following the first lockdown. While some patients wished to return to their previous treatment regimen, most patients managed their medication well and showed good adherence. We also noticed an increase of treatment admissions that are likely related to the relaxed regulations. Previously, the strict therapeutic framework of visiting a HAT centre twice a day for supervised dispensing seemed to have discouraged these individuals from seeking medical treatment. From a medical point of view, the politically driven restrictions on take-home doses in heroin-assisted treatment are questionable and do not support the goal of harm reduction.

The treatment of pertussis with gold tribromide

Summary Whooping cough is a serious disease in its mortality rate, complications, and sequelae. It affects all races in all climates. It is essentially a disease of childhood. The etiology of pertussis is still not definitely established. The anatomic pathology shows an inflammation and degeneration of the upper respiratory tract. Physiologically, there is a hyperirritability of the coughing reflex are which responds to the slightest physical or psychic stimuli. Most of the treatments recommended for whooping cough are either ineffectual or not practical of application. As a result of a study of many drugs, especially the bromides, in the treatment of whooping cough, gold tribromide is seemingly an effective remedy in a large number of cases. The earlier in the disease the treatment is begun, the quicker and better the results. The compound of gold tribromide inhibits the coughing reflex are, allays the general nervous irritability and relieves the spasmodic attacks which cause damage to every system of the body.