Luminescent (N^C^C) Gold(III) Complexes: Stabilized Gold(III) Fluorides

We report the design, synthesis, and application of a (N^C^C)‐ligand framework able to stabilize highly electron‐deprived gold(III) species. This novel platform enabled the preparation of C(sp²)‐gold(III) fluorides for the first time in monomeric, easy‐to‐handle, bench‐stable form by a Cl/F ligand‐exchange reaction. Devoid of oxidative conditions or stoichiometric use of toxic Hg salts, this method was applied to the preparation of multiple [C(sp²)‐Au^III‐F] complexes, which were used as mechanistic probes for the study of the unique properties and intrinsic reactivity of Au? F bonds. The improved photophysical properties of [(N^C^C)Au^III] complexes compared to classical pincer (C^N^C)‐Au systems paves the way for the design of new late‐transition‐metal‐based OLEDs.     

Gold(I) and Gold(III) Trifluoromethyl Derivatives

Trifluoromethylation of AuCl₃ by using the Me₃SiCF₃/CsF system in THF and in the presence of [PPh₄]Br proceeds with partial reduction, yielding a mixture of [PPh₄][Au^I(CF₃)₂] ( 1′ ) and [PPh₄][Au^III(CF₃)₄] ( 2′ ) that can be adequately separated. An efficient method for the high‐yield synthesis of 1′ is also described. The molecular geometries of the homoleptic anions [Au^I(CF₃)₂]^? and [Au^III(CF₃)₄]^? in their salts 1′ and [NBu₄][Au^III(CF₃)₄] ( 2 ) have been established by X‐ray diffraction methods. Compound 1′ oxidatively adds halogens, X₂, furnishing [PPh₄][Au^III(CF₃)₂X₂] (X=Cl ( 3 ), Br ( 4 ), I ( 5 )), which are assigned a trans stereochemistry. Attempts to activate C? F bonds in the gold(III) derivative 2′ by reaction with Lewis acids under different conditions either failed or only gave complex mixtures. On the other hand, treatment of the gold(I) derivative 1′ with BF₃?OEt₂ under mild conditions cleanly afforded the carbonyl derivative [Au^I(CF₃)(CO)] ( 6 ), which can be isolated as an extremely moisture‐sensitive light yellow crystalline solid. In the solid state, each linear F₃C‐Au‐CO molecule weakly interacts with three symmetry‐related neighbors yielding an extended 3D network of aurophilic interactions (Au???Au=345.9(1) pm). The high $\tilde \nu $ _CO value (2194 cm^?1 in the solid state and 2180 cm^?1 in CH₂Cl₂ solution) denotes that CO is acting as a mainly σ‐donor ligand and confirms the role of the CF₃ group as an electron‐withdrawing ligand in organometallic chemistry. Compound 6 can be considered as a convenient synthon of the “Au^I(CF₃)” fragment, as it reacts with a number of neutral ligands L, giving rise to the corresponding [Au^I(CF₃)(L)] compounds (L=CNtBu ( 7 ), NCMe ( 8 ), py ( 9 ), tht ( 10 )).     

Gold Nanoparticle Modified Screen Printed Electrodes for the Trace Sensing of Arsenic(III) in the Presence of Copper(II)

Gold ensembles for the trace level sensing of arsenic(III) in the presence of copper(II) are reported. The gold ensembles are fabricated using citrate capped gold nanoparticles which are chemically synthesised in an aqueous solution with an aliquot of this simply cast onto an economical and disposable screen printed electrode. After drying at room temperature, the gold ensembles are ready for use. The gold ensembles are explored towards the sensing of arsenic(III) in the presence of copper(II) using anodic stripping voltammetry where the corresponding stripping peaks are well resolved and using this protocol it is possible to readily detect 3 µg L^?1 (3 ppb) with a detection limit of 0.4 µg L^?1 (0.4 ppb). Proof‐of‐concept is also shown for the sensing of arsenic(III) in a canal water sample. Given the low cost of the sensor and ease of fabrication, the gold ensembles hold promise for the sensing of arsenic(III) in water samples where copper(II) may be present.     

Oxinkomplexe von Gold(III) und Titan(III)

Ohne Zusammenfassung     

Complementary Iron(II)‐Catalyzed Oxidative Transformations of Allenes with Different Oxidants

Substituent‐ and oxidant‐dependent transformations of allenes are described. Given the profound influence of the substituent on the reactivity of allenes, the subtle differences in allene structures are manifested in the formation of diverse products when reacted with different electrophiles/oxidants. In general, reactions of nonsilylated allenes involve an allylic cation intermediate by forming a C?O bond, at the sp‐hybridized C2, with either DDQ (2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone) or TBHP (tert‐butyl hydroperoxide), along with FeCl₂?4 H₂O (10 mol %). In contrast, silylated allenes favor the formation of propargylic cation intermediates by transferring the allenic hydride to the oxidant, thus generating 1,3‐enynes (E1 product) or propargylic THBP ethers (S_N1 product). The formation of these different putative cationic intermediates from nonsilylated and silylated allenes is strongly supported by DFT calculations.     

Complexation of Lanthanum(III) and Terbium(III) with 5-Br-PAAP in the Presence of Surfactants

The complexation of lanthanum(III) and terbium(III) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PAAP) in the presence of surfactants was studied by spectrophotometry. Optimal conditions of interaction and chemical and analytical characteristics of the resulting complexes were determined. Molar absorptivities are 7.8 × 10⁴ (La) and 8.7 × 10⁴ (Tb). The effect of the ionic strength of the solution and concentration of the organic solvent on the conditions of complexation in the presence of surfactants was considered. Correlation equations relating all chromaticity characteristics to the concentration of lanthanum, terbium, and erbium in the range 5–25 g per 25 mL were deduced. It was demonstrated tat the use of the most sensitive chromaticity functions (yellowness, chromaticity coordinates, color saturation, etc.) increases the sensitivity of the determination by a factor of 25–100 in comparison with the photometric method.     

Determination of Trace Iron(II) in the Presence of Iron(III)

The determination of trace iron(II) is usually interfered by the presence of iron(III) when ortho-phenanthroline colorimetric method is used. In this report a chromogenic reagent which contains ortho-phenanthroline-EDTA mixture has been developed to decrease the interference of ferric ion after adjusting the acidity of sample at 0.1 N by adding the sulfuric acid. The procedure is also simplified by introducing sulfamate buffer solution (pH= 1.5) without adjusting the acidity of sample with sulfuric acid. If iron(III) is not present in the sample, this method is also applicable. The comparative results are exhibited for the present method and the conventional o-phenanthroline method.     

Gold(III) porphyrin-catalyzed cycloisomerization of allenones

[reaction: see text] Gold(III) porphyrin-catalyzed cycloisomerization of allenones gave the corresponding furans in good to excellent yields (up to 98%) and with quantitative substrate conversions. By recovering the Au(III) catalyst, a recyclable catalytic system is developed with over 8300 product turnovers attained for the cycloisomerization of 1-phenyl-buta-2,3-dien-1-one. The versatility of the gold(III) porphyrin catalyst was exemplified by its application to the hydroamination and hydration of phenylacetylene in 73% and 87% yield, respectively.     

Gold(I) and gold(III) corroles

Corrole complexes with gold(I) and gold(III) were synthesized and their structural, photophysical, and electrochemical properties investigated. This work includes the X-ray crystallography characterization of gold(I) and gold(III) complexes, both chelated by a corrole with fully brominated β-pyrrole carbon atoms. The mononuclear and chiral gold(I) corrole appears to be the first of its kind within the porphyrinoid family, while the most unique property of the gold(III) corrole is that it displays phosphorescence at ambient temperatures.     

Electrolytic Deposition of Cobalt(III) Oxide in the Presence of Nickel(II) and Chromium(III) Ions

Preparation conditions and nature of anodic processes in electrolytic deposition of cobalt(III) oxide in the presence of nickel(II) and chromium(III) ions from mixed aqueous solutions of their sulfates were studied. The deposits obtained are of interest for creating effective cathode materials for lithium batteries.     

Gold(III) Macrocyclic Complexes in Aqueous Solution

Synthesis of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III) perchlorate is described. The behavior of complex cations of gold(III) with macrocyclic ligands—N,N"-bis(2-aminoethyl)-2,4-pentanediiminatogold(III) (A²⁺) and 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III) (B⁺)—is studied in aqueous solutions. The formation of A²⁺and B⁺complexes and the protonation of a B⁺complex are investigated, and the solubility products are determined for perchlorate salts of A²⁺and B⁺cations. The six-membered -diiminate rings of the complex cation B⁺are suggested to be nonequivalent in aqueous solutions: one of them either undergoes intramolecular rearrangement or becomes entirely open.     

The Spectrophotometry Determination of Mn(III) in the Presence of Mn(IV)

Abstract

The spectra of complex of Mn(III) and Mn(IV) with pyrophosphoric acid are investigated. The molar absorption coefficient of the complex of Mn(III) with pyrophosphoric acid is 80.6/Mcm at 510nm which is close to that of Mn(IV), 110/Mcm, however, the molar absorption coefficient of the complex of Mn(HI) with pyrophosphoric acid is only 4.98/Mcm at 398nm which is much less than that of Mn(IV), 390/Mcm. Based on this absorbance difference between Mn(III) and Mn(IV) at wavelength 398nm and 510nm, a procedure of determination of Mn(III) in the presence of Mn(IV) has been developed.     

A Nucleophilic Gold(III) Carbene Complex

The first Au^III carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometalated Au^III precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high‐energy highest occupied molecular orbital (HOMO) centered at the carbene center suggests nucleophilic character for the Au^III carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS₂), resulting in two types of C=C coupling reactions.     

Photoinitiated Reactions of Haloperfluorocarbons with Gold(I) Organometallic Complexes: Perfluoroalkyl Gold(I) and Gold(III) Complexes

The study of perfluoroalkyl metal complexes is key to understand and improve metal-promoted perfluoroalkylation reactions. Herein, we report the synthesis of the first gold complexes with primary or secondary perfluoroalkyl ligands by photoinitiated reactions between Au^I organometallic complexes and iodoperfluoroalkanes. Complexes of the types LAuR_F (L=PPh₃ or N,N-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; R_F=n-C₄F₉, n-C₆F₁₃, i-C₃F₇, c-C₆F₁₁) and [Au(R_F)(Ar)I(PPh₃)] (Ar=2,4,6-trimethylphenyl) have been isolated and characterized. Alkynes R_FC≡CR were formed by reaction of Ph₃PAuC≡CR (R=Ph, nHex) with IR_F (R_F=n-C₄F₉, i-C₃F₇). According to the evidences obtained, this transformation undergoes through a photoinitiated radical mechanism. Au^III complexes [Au(n-C₄F₉)(X)(Y)L] (X=Y=Cl, Br, I, Me; X=Me, Y=I) have been prepared or in situ generated, and their thermal or photochemical decomposition reactions have been studied.     

Gold(III) and platinum(II) complexes of hexamethylenetetramine

Gold(III) trichloride and platinum(II) dichloride form 1:1 complexes with hexamethylenetetramine. The compounds prepared were characterized by the elemental analysis, infrared,Raman,¹H-NMR, and¹³C-NMR spectroscopy, and conductivity measurements.     

Gold(III) amine complexes in aqueous alkali solutions

The gold(III) 1,3-diaminopropane complex [Au(1,3-pn)(1,3-pn-H)]Cl₂ has been synthesized. Its dissociation constant has been determined: Au(1,3-pn)₂³⁺ = Au(1,3-pn-H)²⁺ + H⁺, logK _a1 = −7.03 ± 0.05 (I = 0.1 mol/L NaClO₄). Considerable spectral changes are observed for strong alkali solutions (pH 11–14) containing the monoamido forms of the gold(III) ethylenediamine, 1,3-diaminopropane, and diethylenetriamine complexes (Au(en)(en-H)²⁺, Au(1,3-pn)(1,3-pn-H)²⁺, Au(dien-H)OH⁺). These changes are attributed to the formation of the diamido species Au(en-H)₂⁺, Au(1,3-pn-H)₂⁺, and Au(dien-2H)OH⁰. The dissociation constants of the monoamido complexes have been determined: Au(en)(en-H)²⁺ (logK _a2 = −10.9 ± 0.1 at I = 0.001–0.01 mol/L NaCl); Au(1,3-pn)(1,3-pn-H)²⁺ (logK _a2 = −11.3 ± 0.1 at I = 0.1 mol/L NaCl); Au(dien-H)OH⁺ (logK _a2 = −12.4 ± 0.1 at I = 0.1 mol/L NaCl).     

Gold(III) fluorosulfate as an initiator of the polymerization

Gold(III) fluorosulfate was shown to have potential for initiating the polymerization and graft copolymerization of tetrahydrofuran (THF) and similar monomers at room temperature. Addition to THF of either gold(III) fluorosulfate or of gold(III) fluorosulfate and acetyl chloride (a model for a reactive polymer backbone) led to high yields (60–70%) of polytetrahydrofuran. IR, NMR, HPLC, and other studies were used to determine the mechanism of initiation in each case. They showed that in the absence of halide, the gold salt led to hydrogen abstraction from THF and formation of protonic acid, which then initiated polymerization. In the presence of halide, concurrent initiation due to the formation of tertiary oxonium ion by acetylation occurred. Gold(III) chloride precipitated simultaneously.     

ChemInform Abstract: Relativistic Effects in Gold Chemistry. Part 4. Gold(III) and Gold(V) Compounds

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