G. A. Kostin

Thiacalix[4]arenes: Extraction of palladium and the electronic structure

The extractability of palladium nitro complexes with the charge state of sulfur and oxygen atoms in thiacalix[4]arenas in the cone and 1,3-alternate conformations are compared. The results of X-ray photoelectron and X-ray emission studies indicate the presence of considerable electron density on the bridging sulfur atoms, which is due to the contribution of the sulfur 3p AO to the upper occupied MOs of molecules. A series of changes in the electron density on sulfur atoms in the order calixarene thioethers > thiacalixarenes > dialkylsulfides ((C10H21)2S) > (C6H5)2S not completely coincide with changes in their extrability, which can be caused by different nature and stoichiometry of the formed palladium complexes.

Two Oxygen-Coordinated Metastable Ru–ON States for Ruthenium Mononitrosyl Complex

The properties of Ru-ON states were studied in cis-[RuNO(NH3)2(NO2)2OH] under illumination. The structure contains two nonequivalent complexes, and the metastable state was generated for both molecules with 19(1) and 31(1)% populations. The MS1 thermal decay occurs as a one-step process at about 240 K according to differential scanning calorimetry (DSC). For the first-order reaction, the frequency factor and activation energy for the decay process were determined as 2.0(2) × 10(13) s(-1) and 68.3(4) kJ mol(-1), respectively. Also, the simultaneous metastable state decay observed via DSC was in agreement with IR spectroscopy.

Extraction of palladium with acyclic analogs of thiacalix[4]arenes from nitric acid solutions

Abstractp-tert-Butylcalix[4]arene was compared with its acyclic analogs in palladium extraction from nitric acid solutions as mononuclear and poly(bi)nuclear complexes with participation of protonated molecules of podands and macrocycle. The extraction ability of podands is similar to that of macrocycle because of the same character of complexation (Pd: S = 1: 1) without formation of new chelates and lower than that of monodentate analog owing to formation of a square complex (Pd: S = 1: 2).

XPS, XES, and quantum chemical investigation of the electronic structure of thiacalix[4]arenes and calix[4]arene thioesters

The X-ray photoelectron and X-ray emission spectra as well as the charge state of thiacalix[4]arenes in the cone and 1,3-alternate conformations and calix[4]arene thioesters were studied. The donor ability of sulfur bridging atoms in the studied compounds was shown to be close to that in dialkyl sulfides. The internal X-ray transitions (Kα and Kβ) were described by the energy of Kohn-Sham orbitals calculated by DFT method with relaxation corrections.

X-ray spectral and quantum chemical study of the electronic structure of thiacalix[4]-arenes and their acyclic analogs

An X-ray photoelectron and X-ray emission study of the charge state of thiacalix[4]arenes is performed with a comparison with the data of quantum chemical calculations. Relaxation corrections between the Kohn-Sham orbital energies calculated by the DFT method and experimental parameters of the X-ray emission and photoelectron spectra of the studied compounds are estimated. It is shown that the formation of a cyclic aromatic system in thiacalixarenes results in a decrease in the energy of orbitals involving p-π interactions of the bridging sulfur atoms and aromatic moieties, which determines the features of the X-ray emission spectra of the studied compounds.

Some features found in the extraction of platinum group metals and gold with calix[4]arenamines and calix[n]arene thioethers from hydrochloric acid solutions

Extraction of platinum group metals and gold from hydrochloric acid solutions with calix[4]arenamines (CAA) and calix[n]arene thioethers (n = 4, 6; CTE) was studied. The high macrocyclic effects (102–103) are due to chelation between metals and the donor centers of macrocycles in the systems CAA-Pd and CTE-Ag, PtII, and PtIV. New CAA-based extracting systems for collective extraction of Pd, Pt, Au, Ir, and Rh and new CTE-based systems for separation of Au and Pd from Ag and Pt were justified.

Palladium and silver extraction with thiacalix[4]arenes and their acyclic analogs from carbonate and ammonia-carbonate solutions

A quantitative comparison of palladium and silver extraction with p-tert-butylthiacalix[4]arene (TCA) from nitric acid, carbonate, ammonia-carbonate, and ammonia solutions was carried out. It was shown that TCA under optimal conditions can be used for concurrent extraction of palladium and silver from carbonate systems of CARBEX process, selective recovery of palladium from nitric acid solutions, and selective silver extraction from ammonia-carbonate solutions. Metal distribution ratios and effective extraction constants decrease when the complex-forming ability of aqueous phase rises (Na2CO3 > NH4HCO3). The ammonia complexation of Ag+ is determining factor for silver, solution pH plays a certain role for palladium due to formation of hydroxo complexes.

Electronic structure of calix[4]arene thioethers and their complexes with palladium, as studied by X-ray emission spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry

The charge state of calix[4]arene thioethers and their complexes with palladium was studied by X-ray emission spectroscopy and X-ray photoelectron spectroscopy. Experimental data were compared with the results of quantumchemical calculations. The involvement of the sulfur lone electron pairs in the coordination to Pd atoms causes a decrease in the energies of the corresponding MOs having contributions from the sulfur 3p AOs and, consequently, a decrease in the intensity of the maximum A on going from the S(Kβ) spectra of free ligands to the spectra of complexes. The binuclear nature of the complexes does not lead to the onset of significant additional interactions between two metal centers.

High thermal stability of the Ru-ON (MS1) linkage isomer of ruthenium nitrosyl complex [RuNO(Py)4F](ClO4)2 with trans NO-Ru-F coordinate.

The reaction of [RuNO(Py)4OH](PF6)2 with hydrofluoric acid results in the formation of the [RuNO(Py)4F]2+ cation with good yield. The perchlorate salt [RuNO(Py)4F](ClO4)2 was separated and characterized by elemental analysis, IR spectroscopy, and single crystal and powder X-ray diffraction. Though the crystal structure of the salt contained two crystallographically independent [RuNO(Py)4F]2+ cations, the bond distances differed by no more than 0.005 A, and only one ν(NO) vibration band (1907 cm−1 at room temperature) was observed in the IR spectra of the salt. Blue light irradiation (445 nm) at 80 K resulted in the formation of the MS1 linkage isomer with Ru–ON coordination which could be converted to the MS2 linkage isomer (Ru–η2NO coordination) upon IR (980 nm) irradiation. The achieved conversion is equal to 20–23% for the MS1 isomer and 17% for the MS2 isomer. The thermal decay of both metastable isomers was investigated by IR spectroscopy and DSC. The decay temperature for the MS2 isomer was 185 K. For the MS1 isomer, the decay temperature of [RuNO(Py)4F](ClO4)2 (289–291 K) was the highest of all known ruthenium nitrosyl complexes.

Ruthenium sorption as heterometallic complexes with phosphoryl-containing impregnated sorbents

It is shown that the main features of ruthenium extractive recovery with neutral organophosphorus compounds (L) as [RuNO(NO2)4MLn] (M = Zn, Cu, Co, Ni; n = 2–3) heterometallic complexes are retained on the sorption recovery with sorbents impregnated with L. The sorbent based on mixed trialkylphosphine oxide can be used for the chromatographic recovery of ruthenium, the extent of total ruthenium recovery at sorption-desorption stages (90–94%) retains after seven cycles.