Lewis Acid Coupled Electron Transfer of Metal–Oxygen Intermediates

Redox‐inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal–oxygen intermediates, such as metal–oxo and metal–peroxo complexes. The mechanisms of the oxidative C?H bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)–oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)₃ have been unified as rate‐determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)₃) by iron(III)–oxo complexes. All logarithms of the observed second‐order rate constants of Lewis acid‐promoted oxidative C?H bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)–oxo complexes exhibit remarkably unified correlations with the driving forces of proton‐coupled electron transfer (PCET) and metal ion‐coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)₃ to the metal–oxo moiety has been confirmed for Mn^IV–oxo complexes. The enhancement of the electron‐transfer reactivity of metal–oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox‐inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)–peroxo complexes, resulting in acceleration of the electron‐transfer reduction but deceleration of the electron‐transfer oxidation. Such a control on the reactivity of metal–oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca²⁺ in the oxidation of water to dioxygen by the oxygen‐evolving complex in photosystem II.     

The Reaction of Selenium Trioxide with Dialkyl Ethers

The donor‐acceptor complexes Et₂O·SeO₃ and (Me₂O)₂·SeO₃ can be obtained as primary products by the reactions of selenium trioxide with dimethyl ether (Me₂O) and diethyl ether (Et₂O). The crystal and molecular structure of both complexes, which are stable below their melting points only, was determined by X‐ray structure analysis. Pairs of molecules Et₂O·SeO₃ form dimers due to two weak intermolecular Se···O contacts. No intermolecular interactions were observed in (Me₂O)₂·SeO₃. Trigonal bipyramidal coordination around Se^VI atoms in the latter complex is almost undistorted. Conversion of the adducts to dialkylesters of diselenic and selenic acid in the liquid phase was monitored by Raman, ¹H‐ and ⁷⁷Se‐NMR spectroscopy.     

Selenium‐Modified Microgels as Bio‐Inspired Oxidation Catalysts

Active colloidal catalysts inspired by glutathione peroxidase (GPx) were synthesized by integration of catalytically active selenium (Se) moieties into aqueous microgels. A diselenide crosslinker (Se X‐linker) was successfully synthesized and incorporated into microgels through precipitation polymerization, along with the conventional crosslinker N,N′‐methylenebis(acrylamide) (BIS). Diselenide bonds within the microgels were cleaved through oxidation by H₂O₂ and converted to seleninic acid whilst maintaining the intact microgel microstructure. Through this approach catalytically active microgels with variable amounts of seleninic acid were synthesized. Remarkably, the microgels exhibited higher catalytic activity and selectivity at low reaction temperatures than the molecular Se catalyst in a model oxidation reaction of acrolein to acrylic acid and methyl acrylate.     

Thermodynamic investigation of zirconium diselenite

Summary On the basis of calorimetric research of selenium dioxide, zirconium dioxide and zirconium diselenite dissolution reactions in the hydrofluoric acid solution under 298 K a standard enthalpy of Zr(SeO₃)₂ formation reaction from ZrO₂ and SeO₂ and a standard enthalpy of zirconium diselenite formation have been obtained. The value of enthalpy has been equal to -58.1±3.43 kJ mol^-1 in ZrO_2(solid)+2SeO_2(solid) Zr(SeO₃)_2(solid) reaction. The standard enthalpy of zirconium diselenite formation is equal to H_f,298⁰Zr(SeO₃)_2(solid)= -1603.2±3.8 kJ mol^-1. The H_f,298⁰ Zr(SeO₃)_2(solid) value has been determined for the first time.     

Synthesis of Cyclic Peptides by Photochemical Decarboxylation of N‐Phthaloyl Peptides in Aqueous Solution

The synthesis of a variety of cyclic peptides from N‐phthaloyl‐protected di‐, tri‐, tetra‐, and pentapeptides with different aminocarboxylic acid tethers by photodecarboxylation – initiated by intramolecular electron transfer – has been explored in aqueous media. The progress and the chemoselectivity of the follow‐up processes after CO₂ extrusion were traced by the respective pH/time‐profiles, as well as by the overall change in pH after completion of the reaction. The competition between cyclization and simple oxidative decarboxylation depends on spacer length and geometry, H‐bonding interaction between the electron accepting phthalimide C?O groups and amide H‐atoms, as well as the geometric reorganization coupled with the radical combination step and the formation of the lactam rings. With progressing reaction, hydrolysis of the phthalimide chromophore becomes an increasingly important side reaction due to the constant increase in pH. The use of phosphate‐buffered aqueous media consequently improved the cyclization yields. The ground‐state interactions between amide groups and the terminal COO^? group with the imide C?O groups were studied for the model system [N‐(phthaloyl)glycyl]sarcosine ( 1 ) by NMR spectroscopy where the amide (E/Z)‐equilibrium depends on the presence of carboxylate vs. free carboxylic acid, demonstrating the role of H‐bonding and metal coordination.     

(±)-Palstatin的首次全合成研究

以廉价易得的5-溴香草醛和2,4,6-三羟基苯乙酮为起始原料，首次方便,高效地合成了(±)-Palstatin (1).合成的关键步骤为SeO₂促进的氧化环化和Ag₂O催化的氧化偶联反应.     

Pyridoxine‐Derived Organoselenium Compounds with Glutathione Peroxidase‐Like and Chain‐Breaking Antioxidant Activity

One of the vitamin B6 vitamers, pyridoxine, was modified to incorporate selenium in various oxidation states in place of the methyl group in position 2. Such compounds were conveniently accessed by treatment of bis‐4,5‐(carboethoxy)‐2‐iodo‐3‐pyridinol with disodium diselenide and LiAlH₄‐reduction. After work‐up, selone 7 was isolated in good yield as an air‐stable crystalline material. Hydrogen bonding to the neighboring hydroxyl group, as revealed by the short intramolecular Se ??? H distance in the crystal structure is likely to provide extra stabilization to the compound. Computational studies showed that selone 7 is more stable than the corresponding selenol tautomer by 12.2 kcal mol^?1. Hydrogen peroxide oxidation of the selone 7 afforded diselenide 12 , and, on further oxidation, seleninic acid 13 . Treatment of the seleninic acid with thiophenol provided an isolable selenosulfide 14 . The glutathione peroxidase‐like properties of the pyridoxine‐derived compounds were assessed by using the coupled reductase method. Seleninic acid 13 was found to be twofold more active than ebselen. The chain‐breaking capacity of the pyridoxine compounds were studied in a water/chlorobenzene membrane model containing linoleic acid as an oxidizable substrate and N‐acetylcysteine as a thiol reducing agent. Diselenide 15 could match α‐tocopherol when it comes to reactivity towards peroxyl radicals and inhibition time.     

Untersuchungen zum System SmOBr/SeO2

Investigation on the System SmOBr/SeO₂ The existence of three ternary phases SmSeO₃Br, SmSe₂O₅Br and SmSe₃O₇Br on the line SmOBr—SeO₂ in thermodynamically equilibrium has been established for the first time. The phases were synthesized by solid state reaction and characterized by X‐ray and IR‐spectroscopy. The phase barogram and phase diagram were determined by DTA and total pressure measurements. The enthalpies of formation and the standard entropies of the phases were calculated from the vapour pressure data. In addition, the enthalpies of formation were followed from solution calorimetry of the phases and SmOBr and SeO₂, respectively. SmSe₃O₇Br and SmSe₂O₅Br melts peritectically at 350 °C and 600 °C correspondently. SmSeO₃Br shows two diffusion phase transitions in solid state: 160 °C (g‐b) and 375 °C (b‐a).     

Antioxidant activity of the anti-inflammatory compound ebselen: a reversible cyclization pathway via selenenic and seleninic acid intermediates

A revised mechanism that accounts for the glutathione peroxidase (GPx)-like catalytic activity of the organoselenium compound ebselen is described. It is shown that the reaction of ebselen with H(2)O(2) yields seleninic acid as the only oxidized product. The X-ray crystal structure of the seleninic acid shows that the selenium atom is involved in a noncovalent interaction with the carbonyl oxygen atom. In the presence of excess thiol, the Se--N bond in ebselen is readily cleaved by the thiol to produce the corresponding selenenyl sulfide. The selenenyl sulfide thus produced undergoes a disproportionation in the presence of H(2)O(2) to produce the diselenide, which upon reaction with H(2)O(2), produces a mixture of selenenic and seleninic acids. The addition of thiol to the mixture containing selenenic and seleninic acids leads to the formation of the selenenyl sulfide. When the concentration of the thiol is relatively low in the reaction mixture, the selenenic acid undergoes a rapid cyclization to produce ebselen. The seleninic acid, on the other hand, reacts with the diselenide to produce ebselen as the final product. DFT calculations show that the cyclization of selenenic acids to the corresponding selenenyl amides is more favored than that of sulfenic acids to the corresponding sulfenyl amides. This indicates that the regeneration of ebselen under a variety of conditions protects the selenium moiety from irreversible inactivation, which may be responsible for the biological activities of ebselen.     

Synthesis and Structure of Lithium Cadmium Selenite Hydroxide,LiCd2(SeO3)2(OH)

The new compound LiCd₂(SeO₃)₂(OH) has been hydrothermally synthesized and characterized by single‐crystal X‐ray diffraction and IR spectroscopy. It is built up from a network of edge‐ and vertex‐sharing pyramidal [SeO₃]^2— groups, distorted CdO₆ octahedra, and CdO₇ monocapped trigonal prisms. The cadmium‐centred groups form infinite columns, onto which Se atoms (as [SeO₃]^2— groups) are grafted. Cross‐linking between the columns results in a three‐dimensional framework which encapsulates [100] channels occupied by the tetrahedrally‐coordinated lithium cations. The H atom of the hydroxyl group appears to participate in a weak, bifurcated, hydrogen bond. Crystal data: LiCd₂(SeO₃)₂(OH), M_r = 502.67, monoclinic, P2₁/c (No. 14), a = 5.8184 (3)Å, b = 10.2790 (5)Å, c = 11.5021 (5)Å, β = 90.446(1)°, V = 687.89 (9)ų, Z = 4, R(F) = 0.021, wR(F²) = 0.046.     

Trithallium hydrogen bis(sulfate), Tl3H(SO4)2, in the super‐ionic phase by X‐ray powder diffraction

The structure of trithallium hydrogen bis­(sulfate), Tl₃H(SO₄)₂, in the super‐ionic phase has been analyzed by Rietveld analysis of the X‐ray powder diffraction pattern. Atomic parameters based on the isotypic Rb₃H(SeO₄)₂ crystal in space group Rm in the super‐ionic phase were used as the starting model, because it has been shown from the comparison of thermal and electric properties in Tl₃H(SO₄)₂ and M₃H(SO₄)₂ type crystals (M = Rb, Cs or NH₄) that the room‐temperature Tl₃H(SO₄)₂ phase is isostructural with the high‐temperature Rm‐symmetry M₃H(SO₄)₂ crystals. The structure was determined in the trigonal space group Rm and the Rietveld refinement shows that an hydrogen‐bond O—­H?O separation is slightly shortened compared with O—H?O separations in isotypic M₃H(SeO₄)₂ crystals. In addition, it was found that the distortion of the SO₄ tetrahedra in Tl₃H(SO₄)₂ is less than that in isotypic crystals.     

Development of a Bacterial Enzyme-Based Biosensor for the Detection and Quantification of Selenate

An enzymatic biosensor has been developed for the determination of selenate (SeO₄²⁻), in which selenate reductase (SeR) is chemically attached to a gold disk electrode by lipoic acid N-hydroxysuccinimide ester as linker, allowing the catalytic reduction of the SeO₄²⁻ to SeO₃²⁻. Modification of the gold electrode was characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), and electrochemistry. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements were performed in different buffers for selenate determination. Under optimum conditions, the calibration curve was linear over the range 7.0–3900.0 μg L⁻¹ with limits of detection and quantification of 4.97 and 15.56 μg L⁻¹, respectively. The possible interference of the relevant oxyanions SO₄²⁻, NO₃⁻, NO₂⁻, PO₄³⁻ and AsO₄³⁻ in the determination of SeO₄²⁻ was studied. Finally, the proposed biosensor was used to determine SeO₄²⁻ with recovery between 95.2 and 102.4 % in different real water samples.     

SO3H-Functionalized Ionic Liquids: Green, Efficient and Reusable Catalysts for the Facile Dehydration of Aldoximes into Nitriles

Easily synthesized aldoximes have been converted to the corresponding nitriles under very mild conditions by a simple reaction using two halogen‐free SO₃H‐functionalized ionic liquids, 3‐methyl‐1‐(4‐sulfonic acid)butylimi‐ dazolium hydrogen sulfate [MIM(CH₂)₄SO₃H][HSO₄] and 1‐(4‐sulfonic acid)butylpyridinium hydrogen sulfate [PY(CH₂)₄SO₃H][HSO₄], as catalyst and reaction medium without any additional organic solvent. The method was equally effective for aromatic aldoximes bearing electron‐donating and electron‐withdrawing substituents. Taking into account environmental and economical consideration, the protocol presented here has the merits of environmentally friendly, simple operation, easy work‐up and very good yields. The catalysts could be recycled and reused for several times without noticeably decreasing in their catalytic activities.     

Singly versus Doubly Reduced Nickel Porphyrins for Proton Reduction: Experimental and Theoretical Evidence for a Homolytic Hydrogen‐Evolution Reaction

A nickel(II) porphyrin Ni‐P (P=porphyrin) bearing four meso‐C₆F₅ groups to improve solubility and activity was used to explore different hydrogen‐evolution‐reaction (HER) mechanisms. Doubly reduced Ni‐P ([ Ni‐P ]^2?) was involved in H₂ production from acetic acid, whereas a singly reduced species ([ Ni‐P ]^?) initiated HER with stronger trifluoroacetic acid (TFA). High activity and stability of Ni‐P were observed in catalysis, with a remarkable i_c/i_p value of 77 with TFA at a scan rate of 100 mV s^?1 and 20 °C. Electrochemical, stopped‐flow, and theoretical studies indicated that a hydride species [H‐ Ni‐P ] is formed by oxidative protonation of [ Ni‐P ]^?. Subsequent rapid bimetallic homolysis to give H₂ and Ni‐P is probably involved in the catalytic cycle. HER cycling through this one‐electron‐reduction and homolysis mechanism has been proposed previously but rarely validated. The present results could thus have broad implications for the design of new exquisite cycles for H₂ generation.     

The Unique Crystal Structure of the Triclinic Samarium(III) Oxoselenate(IV) Sm2[SeO3]3

Pale yellow, needle‐shaped single crystals of Sm₂[SeO₃]₃ were obtained by heating stoichiometric mixtures of Sm₂O₃ and SeO₂ (molar ratio: 1:3) along with substantial amounts of CsCl as fluxing agent in evacuated sealed silica tubes at 830 °C for one week. According to X‐ray single‐crystal diffraction data, Sm₂[SeO₃]₃ crystallizes triclinic (space group: ) with two formula units per unit cell of the dimensions a = 698.62(7), b = 789.71(8), c = 910.34(9) pm, α = 96.693(5), β = 104.639(5), γ = 115.867(5)°. Its crystal structure contains two crystallographically distinct Sm³⁺ cations in eight‐ and ninefold coordination with oxygen atoms arranged as distorted uncapped or capped square antiprisms (d(Sm³⁺?O^2?) = 232?271 pm). These [(Sm1)O₈] and [(Sm2)O₉] polyhedra share opposite edges and faces to form zigzag chains along [100] with discrete pyramidal [SeO₃]^2? anions bridging units. Further linkage by [SeO₃]^2? anions in [010] direction leads to a three‐dimensional network, which exhibits almost rectangular channels along [111]. These tunnels offer width enough to incorporate the free non‐bonding electron pairs (?lone pairs”?) at the Se⁴⁺ cations, since all nine different Ψ¹‐tetrahedral [SeO₃]^2? groups (d(Se⁴⁺?O^2?) = 165?173 pm, ?(O–Se–O) = 94 – 108°) exhibit a pronounced stereochemical ?lone‐pair”? activity. For not being isotypic with neither triclinic Er₂[SeO₃]₃ (CN(Er³⁺) = 7 and 8) nor the remainder rare‐earth metal(III) oxoselenates(IV) of the composition M₂[SeO₃]₃ (≡ M₂Se₃O₉; M = Sc, Y, La, Ce – Lu), Sm₂[SeO₃]₃ claims a unique crystal structure among them.     

Oxidative C−H/C−H Cross‐Coupling Reactions between N‐Acylanilines and Benzamides Enabled by a Cp*‐Free RhCl3/TFA Catalytic System

By making use of a dual‐chelation‐assisted strategy, a completely regiocontrolled oxidative C?H/C?H cross‐coupling reaction between an N‐acylaniline and a benzamide has been accomplished for the first time. This process constitutes a step‐economic and highly efficient pathway to 2‐amino‐2′‐carboxybiaryl scaffolds from readily available substrates. A Cp*‐free RhCl₃/TFA catalytic system was developed to replace the [Cp*RhCl₂]₂/AgSbF₆ system generally used in oxidative C?H/C?H cross‐coupling reactions between two (hetero)arenes (Cp*=pentamethylcyclopentadienyl, TFA=trifluoroacetic acid). The RhCl₃/TFA system avoids the use of the expensive Cp* ligand and AgSbF₆. As an illustrative example, the procedure developed herein greatly streamlines the total synthesis of the naturally occurring benzo[c]phenanthridine alkaloid oxynitidine, which was accomplished in excellent overall yield.     

Ce2[SeO3]3 and Pr2[SeO3]3: Non‐Isostructural Oxoselenates(IV) of the Light Lanthanoids

The crystal structures of Ce₂[SeO₃]₃ and Pr₂[SeO₃]₃ have been refined from X‐ray single‐crystal diffraction data. The compounds were obtained using stoichiometric mixtures of CeO₂, SeO₂, Ce, and CeCl₃ (molar ratio 3:3:1:1) or Pr₆O₁₁, SeO₂, Pr, and PrCl₃ (molar ratio 3:27:1:2) heated in evacuated sealed silica tubes at 830 °C for one week. Ce₂[SeO₃]₃ crystallizes orthorhombically (space group: Pnma), with four formula units per unit cell of the dimensions a = 839.23(5) pm, b = 1421.12(9) pm, and c = 704.58(4) pm. Its structure contains only a single crystallographically unique Ce³⁺ cation in tenfold coordination with oxygen atoms arranged as single‐face bicapped square antiprism and two different trigonal pyramidal [SeO₃]^2? groups. The connectivity among the [CeO₁₀] polyhedra results in infinite sheets of face‐ and edge‐sharing units propagating normal to [001]. Pr₂[SeO₃]₃ is monoclinic (space group: P2₁/n) with twelve formula units per unit cell of the dimensions a = 1683.76(9) pm, b = 705.38(4) pm, c = 2167.19(12) pm, and β = 102.063(7)°. Its structure exhibits six crystallographically distinct Pr³⁺ cations in nine‐ and tenfold coordination with oxygen atoms forming distorted capped square antiprisms or prisms (CN = 9), bicapped square antiprisms and tetracapped trigonal prisms (CN = 10), respectively. The [PrO₉] and [PrO₁₀] polyhedra form double layers parallel to (111) by edge‐ or face‐sharing, which are linked by nine different [SeO₃]^2? groups to build up a three‐dimensional framework. In both compounds, the discrete [SeO₃]^2? anions (d(Se⁴⁺–O^2?) = 166–174 pm) show the typical Ψ¹‐tetrahedral shape owing to the non‐bonding “lone‐pair” electrons at the central selenium(IV) particles. Moreover, their stereochemical “lone‐pair” activity seems to flock together in large empty channels running along [010] in the orthorhombic Ce₂[SeO₃]₃ and along [101] in the monoclinic Pr₂[SeO₃]₃ structure, respectively.     

Nd2(SeO3)2(SeO4) · 2H2O – a Mixed‐Valence Compound containing Selenium in the Oxidation States +IV and +VI

Pale pink crystals of Nd₂(SeO₃)₂(SeO₄) · 2H₂O were synthesized under hydrothermal conditions from H₂SeO₃ and Nd₂O₃ at about 200 °C. X‐ray diffraction on powder and single‐crystals revealed that the compound crystallizes with the monoclinic space group C 2/c (a = 12.276(1) Å, b = 7.0783(5) Å, c = 13.329(1) Å, β = 104.276(7)°). The crystal structure of Nd₂(SeO₃)₂(SeO₄) · 2H₂O is an ordered variant of the corresponding erbium compound. Eight oxygen atoms coordinate the Nd^III atom in the shape of a bi‐capped trigonal prism. The oxygen atoms are part of pyramidal (Se^IVO₃)^2? groups, (Se^VIO₄)^2? tetrahedra and water molecules. The [NdO₈] polyhedra share edges to form chains oriented along [010]. The selenate ions link these chains into layers parallel to (001). The layers are interconnected by the selenite ions into a three‐dimensional framework. The dehydration of Nd₂(SeO₃)₂(SeO₄) · 2H₂O starts at 260 °C. The thermal decomposition into Nd₂SeO₅, SeO₂ and O₂ at 680 °C is followed by further loss of SeO₂ leaving cubic Nd₂O₃.     

Controlling the Self‐Assembly of a Mixed‐Metal Mo/V–Selenite Family of Polyoxometalates

Five mixed‐metal mixed‐valence Mo/V polyoxoanions, templated by the pyramidal SeO₃^2? heteroanion have been isolated: K₁₀[Mo^VI₁₂V^V₁₀O₅₈(SeO₃)₈]?18 H₂O ( 1 ), K₇[Mo^VI₁₁V^V₅V^IV₂O₅₂(SeO₃)]?31 H₂O ( 2 ), (NH₄)₇K₃[Mo^VI₁₁V^V₅V^IV₂O₅₂(SeO₃)(Mo^V₆V^V‐ O₂₂)]?40 H₂O ( 3 ), (NH₄)₁₉K₃[Mo^VI₂₀V^V₁₂V^IV₄O₉₉(SeO₃)₁₀]?36 H₂O ( 4 ) and [Na₃(H₂O)₅{Mo_18?xV_xO₅₂(SeO₃)} {Mo_9?yV_yO₂₄(SeO₃)₄}] ( 5 ). All five compounds were characterised by single‐crystal X‐ray structure analysis, TGA, UV/Vis and FT‐IR spectroscopy, redox titrations, and elemental and flame atomic absorption spectroscopy (FAAS) analysis. X‐ray studies revealed two novel coordination modes for the selenite anion in compounds 1 and 4 showing η,μ and μ,μ coordination motifs. Compounds 1 and 2 were characterised in solution by using high‐resolution ESI‐MS. The ESI‐MS spectra of these compounds revealed characteristic patterns showing distribution envelopes corresponding to 2? and 3? anionic charge states. Also, the isolation of these compounds shows that it may be possible to direct the self‐assembly process of the mixed‐metal systems by controlling the interplay between the cation “shrink‐wrapping” effect, the non‐conventional geometry of the selenite anion and fine adjustment of the experimental variables. Also a detailed IR spectroscopic analysis unveiled a simple way to identify the type of coordination mode of the selenite anions present in POM‐based architectures.     

Thermochemische Untersuchungen zum quasibinären System YbOCl/SeO2

Thermochemical Investigations on the Pseudobinary System YbOCl/SeO₂ On the pseudobinary section YbOCl/SeO₂ four thermodynamically stable compounds exist in accordance with the thermal decomposition and the phase analysis of defined powder mixtures: YbOCl · 3 SeO₂ = YbSe₃O₇Cl, YbOCl · 2 SeO₂ = YbSe₂O₅Cl and YbOCl · SeO₂ = YbSeO₃Cl as well as the YbOCl‐rich phase Yb₂SeO₄Cl₂ (2 YbOCl · SeO₂). The phase barogram and the phase diagram of the pseudobinary section YbOCl/SeO₂ were set up by total pressure measurements and DTA. From the temperature dependence of the decomposition pressures the enthalpies of formation and the standard entropies of the phases were deduced. In addition, the enthalpies of formation of the new compounds were determined from the enthalpies of solution of YbOCl, SeO₂ and the quaternary phases.