Vibrational interactions in dimethylgold(III) halides and carboxylates

The far-infrared and Raman spectra of binuclear molecules [Me₂AuX]₂ (X = Cl, Br, I) and [Me₂Au(OOCR)]₂ (R = Me, CF₃, Bu^t, Ph) in the 600–70 cm⁻¹ region are reported. The experimentally measured vibrational frequencies of [Me₂AuX]₂ are in a good agreement with density functional theory predictions. The Au…Au vibrational interactions predicted to be in the 270–60 cm⁻¹ region of [Me₂AuX]₂ far-IR and Raman spectra have been observed. The Raman-active Au…Au vibrations of the [Me₂Au(OOCR)]₂ molecules were found to be in the same region as those of [Me₂AuX]₂. The Au–X stretching modes were observed between 100 and 250 cm⁻¹ in accordance with the DFT predictions. Their frequencies in the IR spectra of [Me₂AuX]₂ increase in the sequence I < Br < Cl while the AuC₂ stretching frequencies decrease in the same order. This fact might be an evidence of the decreasing covalent character of the gold-halogen bridges. The Au–O stretching bands of dimethylgold(III) carboxylates have been observed in the 500–250 cm⁻¹ region, and Au–C stretching frequencies of both [Me₂AuX]₂ and [Me₂Au(OOCR)]₂ compounds have been found between 600 and 500 cm⁻¹.     

Thermal behaviour of dimethylgold(III) carboxylates

The thermal properties of dimethylgold(III) carboxylates of general formula [(CH₃)₂Au(OOCR)]₂ (R=methyl (1), tert-buthyl (2), trifluoromethyl (3), or phenyl (4)) in solid state have been investigated by the thermogravimetric analysis. The temperature dependences of saturated vapour pressure of complexes have been studied by the Knudsen effusion method with mass spectrometric indication. The thermodynamic parameters Δ_sub H _T ⁰ and Δ_sub S _T ⁰ of the sublimation processes have been calculated. Thermal decomposition of the vapour of complexes 1 and 2 has been studied by means of high temperature mass spectrometry in vacuum, and by-products of decomposition have been determined.     

Synthesis and crystal structure of dimethylgold(III) carboxylates

Three novel carboxylate complexes were synthesized: dimethylgold(III) trifluoroacetate [Me₂Au(Tfa)]₂ (I), trimethylacetate (pivalate) [Me₂Au(Piv)]₂ (II), and benzoate [Me₂Au(OBz)]₂ (III). The starting reagent was [Me₂AuI]₂. The procedure of its synthesis provides 60% product yield. Dimethylgold(III) carboxylates were identified from the IR and ¹H NMR data. The title compounds were studied by X-ray diffraction. The unit cell parameters for I, C₈H₁₂Au₂F₆O₄: a = 15.5522(13), b = 12.9398(11), c = 15.6555(14) Å, β = 104.308(2)°, Z = 8, ρ(calcd.) = 2.959 g/cm³, space group C2/c, R = 0.0779; for II, C₁₄H₃₀Au₂O₄: a = 10.3025(3), b = 15.5952(4), c = 12.6819(3) Å, β = 105.8270(10)°, Z = 4, ρ(calcd.) = 2.224 g/cm³, space group P2₁/c, R = 0.0229; for III, C₁₈H₂₂Au₂O₄: a = 12.8050(2), b = 19.7886(3), c = 7.60300(10) Å, Z = 4, ρ(calcd.) = 2.401 g/cm³, space group Pnma, R = 0.0144. Compounds I–III have the molecular structures; the structural units are the [(CH₃)₂Au(OOCR)]₂ dimers (Au…Au 2.984–3.080 Å), R = CF₃, tert-Bu, Ph. The gold atoms have the square coordination with two carbon atoms and two oxygen atoms (Au-O 2.120–2.173 Å). The molecules in compounds I–III are united into infinite unidimensional chains connected by van der Waals interactions.     

Intramolecularly coordinated organoantimony(III) carboxylates

The reactions of organoantimony chlorides L^1,2SbCl₂1 and 2 ([2,6-(ROCH₂)₂C₆H₃]⁻, R = Me; L¹ and R = t-Bu; L²) with silver salts of selected carboxylic acids resulted to corresponding organoantimony carboxylates L^1,2Sb(OOCR′)₂, 1a-c (for L¹) and 2a-c (for L²), where R′ = CH₃ for 1a, 2a; R′ = CHCH₂ for 1b, 2b and R′ = CF₃ for 1c, 2c. All compounds were characterized by the help of elemental analysis, ESI-MS, ¹H and ¹³C NMR spectroscopy. The solid state structure investigation using single crystal X-ray diffraction techniques (2a, c) and IR spectroscopy revealed significant differences in coordination mode of both O,C,O chelating ligand and carboxylic groups in this set of compounds. The structure of all compounds in solution of non-coordinating solvent (CDCl₃) was determined by means of variable temperature ¹H, ¹³C, ¹⁹F NMR spectroscopy and IR spectroscopy.     

Thermal properties of dimethylgold(III) 8-hydroxyquinolinate and 8-mercaptoquinolinate

Dimethylgold(III) complexes with 8-hydroxyquinoline Me₂Au(Ox) (I) and 8-mercaptoquinoline Me₂Au(Tox) (II) were synthesized and studied. Complex II obtained for the first time was identified from the elemental analysis, IR, ¹H NMR, and mass spectrometry data. The thermal properties of complexes I, II in condensed state were investigated by thermography. The temperature dependences of the saturated vapor pressure over crystals were measured by the Knudsen effusion method with mass spectrometric recording of the gas phase composition and the thermodynamic characteristics of the sublimation process were determined: for I, log P[Torr] = (14.6 ± 0.3) ? (6.34 ± 0.10) × 10³/(T, K), Δ H _subl ^o = 121.2 ± 1.9 kJ^?1, Δ S _subl ^o = 224.1 ± 4.6 J mol^?1 K^?1 (the temperature interval under study 80–115°C); for II, log P [Torr] = (13.3 ± 0.2) ? (6.30 ± 0.09) × 10³/(T, K), Δ H _subl ^o = 120.5 ± 1.7 kJmol^?1, ΔS _subl ^o = 199.3 ± 3.0 J mol^?1 K^?1 (86–145°C).     

Crystal structure of dimethylgold(III) 8-hydroxyquinolinate and 8-mercaptoquinolinate

A crystal-chemical study of dimethylgold(III) complexes with 8-hydroxyquinoline (CH₃)₂Au(OR) and 8-mercaptoquinoline (CH₃)₂Au(SR) (R = C₉H₆N) was performed. Crystal data for (CH₃)₂Au(OR): a = 8.7133(17) Å, b = 27.875(6) Å, c = 8.6688(17) Å, β = 102.76(3)°, Z = 8, ρ(calc) = 2.401 g/cm³, space group P2₁/c, R = 0.0909; for (CH₃)₂Au(SR): a = 3.5401(7) Å, b = 15.689(3) Å, c = 19.910(4) Å, β = 99.81(3)°, Z = 4, ρ(calc) = 2.361 g/cm³, space group P2₁/c, R = 0.0712. Both structures are molecular and involve neutral (CH₃)₂Au(L) molecules, L = C₉H₆NO or C₉H₆NS. In the structures, the molecules are arranged in stacks joined by van der Waals interactions. The average Au…Au intrastack distances are 3.57 Å and 4.34 Å for (CH₃)₂Au(OR) and 3.5 Å for (CH₃)₂Au(SR).     

Properties and X-ray structural study of volatile dimethylgold(III) β-iminoketonates

Three complexes of dimethylgold(III) of a general formula of (CH₃)₂Au(R¹-CNH-CH-CO-R²) involving β-imino-derivatives of acetylacetone (k-acac), trifluoroacetylacetone (k-tfa), and pivaloyltrifluoroacetone (k-pta) are studied for the first time with single crystal X-ray diffraction. Synthesis and properties of these compounds are presented along with thermal properties determined by the DTA technique. The structures of the compounds in question are based on monomeric complexes. Gold atoms have a slightly distorted square-planar coordination involving oxygen and nitrogen atoms of the β-iminoketonate ligand and two methyl groups. Geometrical characteristics of the coordination cores are the following: bond lengths of Au-C_Me fall within 2.008–2.050 Å; average Au-O and Au-N distances are 2.094 Å and 2.068 Å respectively. In the structure of (CH₃)₂Au(k-acac) gold complexes are joined by hydrogen bonds to give infinite chains with the shortest Au...Au separation of 5.396 Å. In the crystals of the fluorinated compounds coplanar molecules make infinite stacks. The shortest intra-stack Au...Au separation of 3.416 Å is observed for the complex of (CH₃)₂Au(k-pta) that possesses the largest thermal stability among the investigated compounds.     

Catalytic C-phenylation of methyl acrylate with tetraphenylantimony(v) halides and carboxylates

Catalytic C-phenylation of methyl acrylate to methyl cinnamate with the Ph₄SbX complexes (X = F, Cl, Br, OH, OAc, O₂CEt) in the presence of the palladium compounds PdCl₂, Pd(OAc)₂, Pd₂(dba)₃, Pd(Ph₃P)₂Cl₂, and Pd(dppf)Cl₂ (dba is dibenzylideneacetone and dppf is bis(diphenylphosphinoferrocene)) was studied in organic solvents (MeCN, THF, DMF, MeOH, and AcOH). The highest yield of methyl cinnamate (73% based on the starting organometallic compound) was obtained for the Ph₄SbCl—PdCl₂ (1 : 0.04) system in acetonitrile.     

Synthesis,crystal structure,and thermal behavior of dimethylgold(III) acetate

A dimethylgold(III) compound with an acetate fragment [(CH₃)₂AuOCOCH₃]₂ has been synthesized. The complex was identified from the melting point, IR, ¹H NMR, and mass spectrometry data. The temperature dependence of saturated vapor pressure over crystals has been measured and the thermodynamic parameters of sublimation have been determined by Knudsen’s effusion method with mass spectrometric measurements of the composition of the gas phase: ΔH _subl = 100.87 kJ·mol^?1, ΔS _subl = 216.67 J·mol^?1·K^?1. The thermal behavior of the solid compound was investigated by differential thermal analysis. The compound was studied by X-ray diffraction. Crystal data for C₈H₁₈Au₂O₄: a = 12.214(5) Å, b = 14.307(3) Å, c = 7.6635(15) Å; β = 103.39(3)°, Z = 4, d _calc = 2.917 g/cm³, space group P2(1)/c, R = 0.0261. The [(CH₃)₂AuOCOCH₃]₂ dimer complex with an Au...Au distance of 2.989 Å is the structural unit. The gold atom has a square plane environment of two carbon and two oxygen atoms; the Au-O distances vary from 2.118 Å to 2.139 Å. The molecules are arranged in chains linked by van der Waals interactions.     

The structural organization of oligonuclear cobalt(II,III) and cobalt(III) carboxylates

The review deals with the topology of homonuclear carboxylate complexes of cobalt(II, III) and cobalt(III) whose structures are built from the monocarboxylate anions RCOO^– (R is a radical containing no electron-donating substituents), water, and its deprotonated forms.     

Thiosemicarbazide complexes of antimony(III) halides

Some hitherto unknown complexes of thiosermicarbazide (Htsc) and antimony(III) halides have been synthesized in 1,4-dioxane. The elemental analyses have indicated that these compounds are of the type Sb(CH₅N₃S)Cl₃ and Sb(CH₅N₃S)X₃.C₄H₈O₂, where X = Br or I. The electronic and vibration spectral analyses have shown that Htsc acts as a bidentate ligand in these complexes, linking through sulphur and “the hydrazine terminal nitrogen” to Sb(III).     

Synthesis and crystal structure of (2,2,6,6-tetramethyl-3-imino-4-heptene-5-onata)dimethylgold(III)

A novel volatile complex of gold(III), (CH₃)₂Au[C(CH₃)₃C(NH)CHC(O)C(CH₃)₃], was synthesized and studied by the elemental analysis, IR spectroscopy, DTA, and X-ray diffraction analysis. Two crystallographically independent gold complexes have different orientation in a unit cell. The Au atoms in both complexes exhibit slightly distorted square coordination involving the O and N atoms of the β-iminoketonate ligand and two C atoms of the methyl groups. The average lengths of the bonds Au-CH₃, Au-O, and Au-N are 2.034, 2.086, and 2.070 Å, the chelate angle NAuO being 89.4°. The gold complexes are packed in stacks with the distances Au···Au 3.494 Å.     

X-ray diffraction study of volatile complexes of dimethylgold(III) derived from symmetrical β-diketones

Crystal chemical investigation of volatile dimethylgold(III) β-diketonates of the general formula (CH₃)₂AuL [L = acetylacetone (acac), dipivalylmethane (dpm), dibenzoylmethane (dbm)] has been carried out for the first time. The synthetic procedure and structural data are reported; differential thermal analysis (DTA) data are given. The structure of the compounds includes monomeric complex molecules arranged as polymeric stack associates. The gold atom has a plane square environment AuO₂C₂ formed by two oxygen atoms of the bidentate (O,O) ligand and two methyl groups. The geometrical characteristics of the coordination units are the following: in all complexes, the Au-O and Au-C_Me bond lengths and O-Au-O chelate angles are 2.070–2.108 Å, 1.989–2.034 Å, and 89.7-93.7°, respectively. The shortest Au-Au distance (3.475 Å) in the stack is observed for the (CH₃)₂Au(dpm) complex.     

Vibrational assignment of aluminum(III) tris-acetylacetone

The geometry, frequency and intensity of the vibrational bands of aluminum(III) Tris-acetylacetone Al(AA)3 and its 1,3,5-(13)C derivative were obtained by the Hartree-Fock (HF) and Density Functional Theory (DFT) with the B3LYP, B1LYP, and G96LYP functionals and using the 6-31G* basis set. The calculated frequencies are compared with the solid IR and Raman spectra. All of the measured IR and Raman bands were interpreted in terms of the calculated vibrational modes. Most computed bands are predicted to be at higher wavenumbers than the experimental bands. The calculated bond lengths and bond angles are in good agreement with the experimental results. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. Four bands in the 500-390 cm(-1) frequency range are assigned to the vibrations of metal-ligand bonds.     

A robust dimethylgold(III) complex stabilized by a 2-pyridyl-2-pyrrolide ligand

Reaction of isopropyl[(2-pyridyl)alkyl]amines such as N-isopropyl-N-2-methylpyridine or N-isopropyl-N-2-ethylpyridine with aqueous solutions of NaAuCl₄ led to the formation of [LAuCl₂][AuCl₄] in low yields, where L = pyridyl amine bound to gold in a bidentate fashion. Reaction of 2-(3,5-diphenyl-1H-pyrrol-2-yl)pyridine with aqueous NaAuCl₄, however, proceeded with formal loss of HCl and direct formation of the gold(III) amido complex L′AuCl₂, where L′ = deprotonated pyrrolyl ligand. Optimization of the reaction conditions to make the new amido complex identified MeCN:H₂O (1:2) as the best choice of solvent, affording product in 92% yield. This dichloro amido complex is a convenient precursor to L′AuMe₂, which was found to be air-stable and thermally robust.     

Organobismuth(III) and organobismuth(V) carboxylates and their evaluation as paint driers

A range of bismuth and organobismuth carboxylates has been prepared e.g. Bi(carboxylate)₃; PhBi(carboxylate′)₂; and Ph₃Bi(carboxylate″)₂ where carboxylate=octanoate, i.e. 5-ethylhexanoate; carboxylate′=acetate and monomaleate; carboxylate″=acetate, propionate, benzoate, 5-ethylhexanoate, and 0.5 oxalate. A combination of IR (solid) and NMR (solution) studies suggests that in the case of the bismuth(V) compounds the carboxylates may be inequivalent in the crystalline forms but equivalent in solution. The compounds have been tested as driers in two paint formulations, Synolac 50W (linseed-based) and Sorbal P470 (linoleic-rich). Although initially promising results were obtained for Synolac 50W, the shelf life of the bismuth driers was poor. With Sorbal P470, bismuth driers were inferior to established formulations. However, a combination of Bi(OOCH₇H₁₅)₃ with tris(diethyldithiocarbamato)-bismuth(III) out-performed established driers.     

Development of a palladium-catalyzed decarboxylative cross-coupling of (2-azaaryl)carboxylates with aryl halides

A catalytic method for the decarboxylative coupling of 2-(azaaryl)carboxylates with aryl halides is described. The decarboxylative cross-coupling presented is mediated by a system catalytic in both palladium and copper without requiring stoichiometric amounts of organometallic reagents or organoboronic acids. This method circumvents additional synthetic steps required to prepare 2-azaaryl organometallics and organoborates as nucleophilic coupling partners, which are prone to protodemetallation and protodeborylation and produce potentially toxic byproducts.     

Pd(II)-catalyzed decarboxylative allylation and Heck-coupling of arene carboxylates with allylic halides and esters

This work demonstrates an alternative method to prepare allylated arenes and aryl-substituted allylic esters via catalytic decarboxylative C-C bond formation using aromatic carboxylic acids and allylic halides and esters.