20816-12-0

K2NaOsO5.5 and K3NaOs2O 9 were obtained from solid-state reactions of potassium superoxide, sodium peroxide and osmium metal at elevated oxygen pressures. K 2NaOsO5.5 crystallizes as an oxygen-deficient cubic double perovskite in space group Fm3m with a=8.4184(5) A and contains isolated OsO6 octahedra. K3NaOs2O9 crystallizes hexagonally in P63/mmc with a=5.9998(4) A and c=14.3053(14) A. K3NaOs2O9 consists of face sharing Os2O9 pairs of octahedra. According to magnetic measurements K2NaOsO5.5 is diamagnetic, whereas K3NaOs2O9 displays strong antiferromagnetic coupling (TN=140 K), indicating enhanced magnetic interactions within the octahedral pair.

The enthalpy, ΔH0, for the gaseous equilibrium OsO4(g) OsO3(g) + 1/2O2(g) was measured by using high-temperature mass spectrometry.Over the temperature range 1139-1471 K, a second-law heat of reaction ΔH01305(II)=161+/-14kH mol-1 was obtained, which yields the standard enthalpy ΔH0298(II)=164+/-14 kJ mol-1, and a third-law heat of reaction ΔH0298(III)=189+/-7 kJ mol-1 was calculated by using the known and estimated molecular constants for OsO4(g) and OsO3(g), respectively.Because of uncertinities in molecular constants, an average standard enthalpy of ΔH0298(II) and DΗ0298(III), 176+/-29 kJ mol-1, is reported for the equilibrium.From this heat of reaction the heat of formation for gaseous OsO3, ΔfH0298(OsO3)=-163+/-29 kJ mol-1, is obtained, leading to a bond energy for O-OsO3 of 423+/-29 kJ mol-1.The ionization potentials for OsO3 and OsO4 were found to be 11.4+/-0.2 and 12.3+/-0.2 eV, respectively.A small signal of OsO2 was observed, and an upper limit of 12.2+/-0.4 eV for its ionization potential was obtained.It is concluded that osmium films which disappear when exposed to the low earth orbit environment probably do so by forming OsO4(g).

Single crystals of a new twinned hexagonal perovskite compound Sr8Os6.3O24 have been synthesized, and structural and magnetic properties have been determined. The compound crystallizes in a hexagonal cell with lattice parameters a = 9.6988(3) ? and c = 18.1657(5) ?. The structure is an eight-layered hexagonal B-site deficient perovskite with the layer sequence (ccch)2 and represents the first example of a hexagonal structure among 5d oxides adopting a twin option. The sample shows spontaneous ferromagnetic magnetization below 430 K with a small saturation moment of 0.11 μB/Os ion. This is the highest Curie temperature (TC) reported for any bulk perovskite containing only 5d ions at the B site.

Competition of methyltrioxorhenium (MTO) with osmium tetroxide (OsO 4) toward L = pyridine and its derivatives, based on the equilibrium constant for the reaction OsO4·L + MTO = MTO·L + OsO4, has been measured. A successful correlation of log K eq with the Hammett σ constants of the substituents on the ligands was realized. A negative reaction constant, obtained for the reactions, shows that a more positive charge expands on the pyridine nitrogen in the complex MTO·L as compared with the complex OsO4·L. So, the rhenium center acts as a better electron acceptor than osmium center. The thermodynamic parameters have been obtained and an excellent linear relationship was observed between the enthalpy and entropy of the reactions.

From a mole ratio1H NMR Evans method experiment it is found that, in a 2.0 M NaOH aqueous matrix, diamagnetic [OsVIIIO4(OH)n]n?(n = 1, 2) (of d0electron configuration) and trans-[OsVIO2(OH)4]2?species (d2) react in a 1:1 mol ratio to form two paramagnetic OsVIIoxido/hydroxido product species (d1). This result is further validated as the chemical reaction model that best fitted stopped-flow UV–Vis spectroscopy kinetic data is given by OsVIII+OsVI?kCOMkCOM2OsVII. From non-linear least squares fits of stopped-flow UV–Vis spectroscopy kinetic traces the comproportionation reaction rate constants, activation energies (forward: ΔH?(obs), ΔS?(obs)and ΔG?(obs)are 10.3 ± 0.5 kcal mol?1, ?2.6 ± 1.6 cal mol?1K?1and 11.1 ± 0.9 kcal mol?1, respectively; and reverse are ?6.7 ± 1.0 kcal mol?1, ?63.6 ± 3.4 cal mol?1K?1and 12.2 ± 2.0 kcal mol?1respectively) and standard reaction energies (ΔH°rxn(obs), ΔS°rxn(obs)and ΔG°rxn(obs)are 17.1 ± 1.2 kcal mol?1, 61.0 ± 4.3 cal mol?1K?1and ?1.1 ± 2.5 kcal mol?1, respectively) at 298.15 K were determined. Stopped-flow kinetic isotope experiments provide evidence that these redox reactions coincide with the transfer of a proton. A systematic DFT speciation study of OsVIand OsVIIoxido/hydroxido complexes in a simulated aqueous phase (COSMO) yield that the thermodynamically most stable OsVIspecies is the singlet spin state trans-[OsVIO2(OH)4]2?complex and the thermodynamically most stable paramagnetic OsVIIproduct species are a combination of trans-[OsVIIO3(OH)2]?and mer-[OsVIIO3(OH)3]2?species. Using the DFT results, the OsVI& OsVIIIcomproportionation reaction is now proposed to be [OsVIIIO4(OH)2]2?reacts with trans-[OsVIO2(OH)4]2?to yield two trans-[OsVIIO3(OH)2]?species and two hydroxide anions. The DFT-calculated standard reaction energies for this reaction at 298.15 K (e.g. with the PBE functional, ΔH°rxn, ΔS°rxnand ΔG°rxnare 21.13 kcal mol?1, 71.06 cal mol?1K?1and ?0.06 kcal mol?1, respectively) compare exceptionally well with the obtained experimental data.

Osmium pentachloride, a new binary chloride of osmium, has been prepared by the reaction of osmium hexafluoride with excess boron trichloride below room temperature. The pentachloride is isomorphous with rhenium pentachloride and has been characterized by X-ray methods, by infrared and UV-visible spectroscopy, and by magnetic and other physical procedures. Some reactions of the pentachloride are also reported in this paper. Reaction of osmium hexafluoride with carbon tetrachloride, known to be less effective than boron trichloride in halogen-exchange reactions, produces a nonstoichiometric product which probably contains several mixed halides of osmium.

The tendency for silver-rich compounds to form higher agglomerates of silver atoms or ions is well known. The synthesis of Ag13OsO 6 represents the first compound in the Ag/Os/O system. Besides [OsO6]4- octahedra, the compound contains icosahedrally shaped Ag134+ clusters (see picture), which are observed for the first time in solid silver oxides.

Intermetallic phases of noble metals (Ru, Rh, Pd, Os, Ir, Pt and Au) were prepared by controlled thermolysis of coordination polymers on the basis of cyanometallates and trimethyltin units (super-prussian blue derivatives). The thermal reaction was carried out under different atmospheres: oxidizing, inert and reducing, upto 1000 °C. Under oxidizing conditions, intimate mixtures of oxides (SnO2 with RuO2, Rh2O3, IrO2, Pt3O4, respectively) were obtained that could be reduced in a second step to the pure noble metals and intermetallic phases incorporating tin (Ru3Sn7, RhSn2, IrSn4, Ir5Sn7, IrSn2, PdSn2, Pd20Sn13, Pd3Sn2, PtSn, PtSn4, Au5Sn, AuSn were all detected). Under reducing conditions, mixtures of metals and intermetallic phases were obtained that could subsequently be oxidized by further thermal treatment to noble metals on SnO2. This offers a new synthetic pathway to such intermetallics and to noble metals on SnO2 supports.

An ozone-oxygen mixture has been used to generate a number of high oxidation-state transition-metal complexes in aqueous solution at room temperature by simple and safe procedures. Species so prepared include the oxo species [OsVIIIO4], [RuVIIIO4], cis-[OsVIIIO4(OH)2]2-, trans-[OsVIO2(OH)4]2-, [RuVIIO4]-, trans-[RuVI(OH)2O3]2-, [VVO4]3- and the new complex [PPh4]2[Ru2O(μ-OCOEt)2Cl 6] 1 for which the crystal structure is reported; the polyoxometalates K6[MnIVMo9O32]·10H 2O, K8[MnIVW6O24]·6H 2O, [NH4]2[MnIVMo6H6O 24]·20H2O and Na8[CeIVW10O36]·8H 2O; the chloro complexes [MIVCl6]2- (M = Pt, Pd, Ir) and [AuIIICl4]-, and manganic acetate [MnIII(OAc)3]·2H2O. Ozonolytic oxidation of coordinated benzylamine in cis-[RuII(bipy)2(NH2CH2Ph) 2][PF6]2 to coordinated benzonitrile in cis-[RuII(bipy)2(NCPh)2][PF6] 2 is also reported.

The black compounds M (M = Na, K, Rb, or Cs) have been prepared from OsO4 and MI in acetone.They are stable in dry air, but disproportionate immediately in aqueous acid solution to OsVIII and OsIV, and in basic solution to Oss

Novel D-homosteroids of the formula STR1 are disclosed. These compounds exhibit anti-inflammatory activity.

3-Cyclohexenecarboxylic acid reacts with osmium tetraoxide in aqueous buffer solutions in the presence of a variety of pyridines to form osmate(VI) esters of the general formula (RO)2OsO2L2, where L represents the monodentate ligand. The compounds appear to be octahedral osmyl complexes with a trans O=Os=O group. The general kinetic equation describing the formation of the esters is rate = k0[OsO4][S] + k1β1[OsO4][S][L] + k2β2[OsO4][S][L]2 where S is the substrate, 3-cyclohexenecarboxylic acid, and β1 and β2 are the overall stability constants for the osmium tetraoxide-ligand system. The hydrolysis of the uncomplexed ester produces the expected diol and osmium-containing products whose nature is pH dependent. In strong alkali, the osmate(VI) ion is the sole product. At pH 9.5, the initially produced Os(VI) species is oxidized by oxygen to osmium tetraoxide. In water or acid, 1 mol of the initially produced Os(VI) species dismutes to 1/3 mol of OsO4 and 2/3 mol of Os(V), the latter perhaps present as a dimeric oxide. On long standing, both of these products, when present together, are reduced by water to osmium dioxide, OsO2·2H2O. The hydrolysis is pH dependent and is catalyzed by both acid and alkali. H218O experiments show that the hydrolysis proceeds exclusively with osmium-oxygen bond cleavage.

The kinetics of the reactions OsCl6-2 + H2O ?k-1k1 Os(OH2)Cl5- + Cl- have been investigated in HCl medium at 80°; the forward reaction has also been studied at 70-89° in HNO3 medium, in which the aquation product and secondary products are rapidly oxidized to OsO4 and Cl-. In 0.00001-0.1 F HNO3 (μ = 0.5-1.32, NaNO3), and by deduction in HCl of the same acidity, k1 = 3.5 × 10-6 sec.-1 at 79.53° in the dark; Ea = 33.1 ± 0.6 kcal., log pZ = 15.1 ± 0.4 (sec.-1), ΔH°*298 = 32.5 ± 0.6kcal., ΔS°*298 = 841 ± 2 cal. deg.-1, k1 (calcd.) = (6 ± 1) × 10-10sec.-1 at25°. In 0.5-1.32 FHNO3 (μ = 1.32, NaNO3) at 80° the rate of disappearance of OsCl6-2 is up to 30% greater than for 0.00001-0.1 F H+, apparently due to a contribution from oxidation of OsCl6-2 to OsCl6-2 and Cl-. In 0.01-1.32 F HCl (μ = 1.32, NaCl) at 80°, the previously uncharacterized Os(OH2)Cl5- is the only product observed at short reaction times; the rate of loss of OsCl6-2 in 1.32 F H+ (where k = 4.17 × 10-6 sec.-1, close to k1 in 0.00001-0.1 F HNO3, μ = 1.32, at 80°) is ca. 14 times that in 0.01 F H+. Rate runs made in 0.016 F HCl with added low concentrations of different oxidants give k values approaching or nearly equal to k1 for 0.00001-0.1 F HNO3; the abnormally high rates of OsCl6-2 loss in HCl at low acidities may arise from reduction by Cl- of very small amounts of OsCl6-2 to one or more hydrolytically more labile complexes. Chloride anation of Os(OH2)Cl5- was studied at 79.53° in 2.49-3.80 F Cl-, 2.46-3.80 F H+ (μ = (Cl-), KCl). An exact first-order dependence on (Cl-) was not observed, 105k-1 varying from 1.01 to 1.97 M-1 sec.-1; in 3.3-3.8 F HCl k-1 ≈ 2 × 10-5 M-1 sec.-1. The visible and near-ultraviolet absorption spectrum of Os(OH2)Cl5- is reported. Compounds described in the literature as pentachlorohydroxy osmate-(IV) salts, M2[Os(OH)Cl5], are very probably binuclear complexes, M4[Cl5OsOOsCl5]·H2O.