Preparation of phenyl trihalovinyl selenides and selenoxides

Phenyl trichlorovinyl selenide and phenyl 1,2-dichloro-2-bromovinyl selenide were obtained by the addition of phenylselenenyl chloride and bromide to di-chloroacetylene with catalysis by Lewis acids. Hydrogen peroxide oxidation gave the corresponding selenoxides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2400–2402, October, 1991.     

Synthesis and reactivity of an unprecedented osmium(VIII) alkylidene

The synthesis of a family of Os(VIII) alkylidene complexes, the highest oxidation state alkylidenes known to date, and their reactivity toward small organic molecules are reported.     

Reaction of an osmium(VI) nitrido complex with cyanide: formation and reactivity of an osmium(III) hydrogen cyanamide complex

Reaction of [Os(VI)(N)(L(1))(Cl)(OH(2))] (1) with CN(-) under various conditions affords (PPh(4))[Os(VI)(N)(L(1))(CN)(Cl)] (2), (PPh(4))(2)[Os(VI)(N)(L(2))(CN)(2)] (3), and a novel hydrogen cyanamido complex, (PPh(4))(2)[Os(III){N(H)CN}(L(3))(CN)(3)] (4). Compound 4 reacts readily with both electrophiles and nucleophiles. Protonation and methylation of 4 produce (PPh(4))[Os(III)(NCNH(2))(L(3))(CN)(3)] (5) and (PPh(4))[Os(III)(NCNMe(2))(L(3))(CN)(3)] (6), respectively. Nucleophilic addition of NH(3), ethylamine, and diethylamine readily occur at the C atom of the hydrogen cyanamide ligand of 4 to produce osmium guanidine complexes with the general formula [Os(III){N(H)C(NH(2))NR(1)R(2)}(L(3))(CN)(3)](-) , which have been isolated as PPh(4) salts (R(1) = R(2) = H (7); R(1) = H, R(2) = CH(2)CH(3) (8); R(1) = R(2) = CH(2)CH(3) (9)). The molecular structures of 1-5 and 7 and 8 have been determined by X-ray crystallography.     

Ruthenium(III), osmium(VIII) and ruthenium(III) + osmium(VIII) catalysed oxidations ofi-propanol by N-bromosuccinimide in basic solution

Summary The oxidation ofi-propanol (IPA) by N-bromosuccinimide (NBS) in basic solution was investigated separately in the presence of Ru^III, Os^VIII and Ru^III + Os^VIII ions. The order in [IPA] was found to be 0.7, 0.5 and 0.3 respectively in the above three cases in the concentration range studied. The order in [NBS] was unity in the presence of Ru^III chloride but was found to be zero in the case of Os^VIII and Ru^III+Os^VIII catalysis. The order in [metalion] was found to be nearly unity in all the three catalysed reactions. Increase in [^–OH] increased the rate of reaction while addition of succinimide retarded the rate of reaction. Decrease in dielectric constantsof the medium decreased the rate of oxidation. The pseudo first order rate constants (k), zero order rate constants (k₀) and the formation constants (k_f) of the substrate-catalyst complexes and the thermodynamic parameters have been evaluated. Suitable mechanisms in conformity with the experimental observations have been proposed for the three catalysed reactions.     

Polarographic determination of osmium with the osmium(VIII)-cerium(IV)-arsenic(III) system

A highly sensitive and novel polarographic method has been developed for determination of ultratrace amounts of osmium, based on the catalysis of the cerium(IV)-arsenic(III) reaction by osmium(VIII). The reaction rate is monitored by measuring the arsenic(III) with a single-sweep oscillopolarograph. Osmium concentrations from 7.0 x 10(-11) to 5.0 x 10(-9)M can be determined by the initial rate method. The method has been applied to determination of osmium in refined ore and chlorination residues with satisfactory results.     

Spectrophotometric determination of osmium (VIII) with promazine hydrochloride

Promazine hydrochloride is proposed as a new reagent for the spectrophotometric determination of osmium (VIII). The reagent forms orange oxidation product with osmium tetroxide at room temperature in acidic media. The effects of acid concentration, time, temperature, and foreign ions are reported. Beer's law is obeyed in the osmium concentration range 1–10 μg/ml.     

Microdetermination of arsenic(III) and osmium(VIII) through osmium-thiourea reaction

Osmium-thioureau reaction is slow under conditions described in earlier methods. In the present study it has been observed that arsenic(III) catalyzed the reaction. Based on this, qualitative and quantitative methods are described for the determination of both osmium and arsenic. Interference study of 30 ions showed they do not interfere.     

Oxidations by iron(VI). Kinetic study of uncatalysed and osmium(VIII) catalysed oxidation of dimethyl sulphoxide in alkaline medium

Summary Uncatalysed and Os^VIII-catalysed oxidation of dimethyl sulphoxide (DMSO) by potassium ferrate [Fe^VI] has been studied in alkaline medium in the 9.8–11.9 pH range, in the presence of IO ₄ ^– as a stabilizing agent. The order in [Fe^VI] and [DMSO] was found to be unity for the uncatalysed reaction and zero and fractional respectively for the catalysed reaction. The [Os^VIII] order was unity in the catalysed reaction. The rate of oxidation decreased with increase in pH and the order in [H⁺] was fractional for the uncatalysed oxidation. However in the catalysed oxidation, the rate at first decreased and then increased with increase in pH. The effect of changing [IO ₄ ^– ] and [buffer] on the oxidation rate was negligible in both cases. Suitable mechanisms consistent with the observed kinetics have been proposed.     

Oxidation of lysine by ferricyanide in presence of osmium(VIII)

Osmium(VIII) catalysed oxidation of lysine by ferricyanide in excess ferrocyanide shows a complex kinetics. The order in lysine falls, from 1 to 0 while that in ferricyanide increases from 0 to 2 with large increase in lysine concentration. The rates were directly proportional to [Os(VIII)] and {Const.+[Fe(CN) ₆ ⁴ ]}. A suitable mechanism is proposed and discussed.

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Oxidation von lysin mittels ferricyanid in der gegenwart von osmium(VIII)

Zusammenfassung Die von Os(VIII) katalysierte Oxidation von Lysin mit Ferricyanid in überschüssigem Ferrocyanid zeigt eine komplexe Kinetik. Bei starker Steigerung der Lysinkonzentration fällt die Ordnung bezüglich Lysin von 1 auf 0, während bezüglich Ferricyanid eine Erhöhung, von 0 auf 2 festzustellen ist. Die Geschwindigkeitskonstanten waren direkt proportional zu [Os(VII)] und {Const.+[Fe(CN) ₆ ⁴ ]}. Es wird ein möglicher Mechanismus vorgeschlagen und diskutiert.

     

(Salen)osmium(VI) nitrides catalyzed glutathione depletion in chemotherapy

Glutathione depletion provides a promising strategy for the design of non-platinum anticancer drugs. Here we report a series of electrophilic (salen)osmium(VI) nitrides that react with glutathione to generate (salen)osmium(III) ammine compounds. In vitro studies indicate that these osmium(VI) nitrides show comparable cytotoxicity to cisplatin against various carcinoma. Mechanistic studies with the representative compound [Os^VI(N)(L^H)(OH₂)](PF₆) (1, L^H = N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion) suggest that 1 induces glutathione depletion, reactive oxygen species generation, endoplasmic reticulum stress, and in turn triggers death receptor-mediated apoptosis and autophagy in lung cancer cells. In vivo evaluations show that 1 can inhibit tumor xenograft growth effectively with no body weight drop.     

Kinetics of oxidation of butane 2,3-diol by osmium(VIII)

The oxidation of butane 2,3-, propane 1,2-, ethane diol and 2-methoxy ethanol in aqueous alkaline medium by Os(VIII) has been studied. The reaction is base catalyzed and shows first-order kinetics in Os(VIII), whereas the order is less than 1 in butane 2,3-diol [BD]. The rate of oxidation is BD > propane 1,2 > ethane diol ≈ 2-methoxy ethanol. The change in ionic strength has no effect on the rate of reaction. Activation parameters ΔE, PZ, and ΔS* have been evaluated.     

Synthesis of selenoxides by oxidation of selenides with superoxide radical anions and 2-nitrobenzenesulfonyl chloride

Alkyl phenyl selenoxides were produced in excellent yields by oxidation of the corresponding selenides with 2-nitrobenzenesulfonyl chloride and potassium superoxide in dry acetonitrile at −15 °C.     

Reactivities of osmium(VIII), iridium(IV) and platinum(IV) towards glycolaldehyde

Oxidations of glycolaldehyde (GA) to glyoxal by osmium(VIII), iridium(IV) and platinum(IV) have been investigated in aqueous solution, and the orders with respect to each [reactant] determined. The reaction involving iridium(IV) takes place through intermediate formation of free radicals in a MeCO₂Na-MeCO₂H buffer medium, whereas a one-step two-electron transfer process occurs in the oxidations by Os^VIII and Pt^IV in an alkaline medium. Mechanisms consistent with the experimental findings are proposed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Efficient trapping of the intermediates in the photooxygenation of sulfides by aryl selenides and selenoxides

Aryl selenides and selenoxides trap efficiently the intermediates in the reaction of singlet oxygen with sulfides. In the co-photooxygenation of 1 equiv of an aryl selenoxide with 1.3 equiv of dimethyl sulfide, the aryl selenone is formed quantitatively. Aryl selenides require 4-5 equiv of sulfide for their complete co-oxidation to selenones.     

A rapid method for the spectrophotometric determination of palladium(II) and osmium(VIII)

Propionyl promazine phosphate is proposed as a new reagent for the rapid spectrophotometric determination of microgram amounts of Pd(II) and Os(VII). PPP instantaneously forms an orange-red 1:1 complex with Pd(II) in sodium acetate-hydrochloric acid buffer of pH 0.8 to 4.0 at room temperature. The reagent also forms an orange-red radical cation with Os(VIII) in 0.5 to 2.0 M hydrochloric acid. The Pd-PPP complex exhibits an absorption maximum at 490–500 nm with molar absorptivity of 7.1 × 10³ liter mol^?1 cm^?1. The Os-PPP radical cation has an absorption maximum at 505–515 nm with molar absorptivity of 2.21 × 10⁴ liters mol^?1 cm^?1. The Sandell sensitivity is 0.022 μg/cm² (Pd) and 0.008 μg/ cm² (Os). Beer's law is valid over the concentration range 0.2 to 21 ppm (Pd) and 0.2 to 4.2 ppm (Os). The proposed method offers the advantages of simplicity, rapidity, and without the need for heating or extraction. The reagent is used for the determination of Pd in the synthetic mixtures corresponding to Pd alloys used in jewelery and Os in osmiridium alloy.     

One-Pot Synthesis of Dihalo(porphyrinato)osmium(IV) Complexes. Evidence for Monohalo(carbonyl)osmium(III) Intermediates

trans-Dichloro-, trans-dibromo-, and trans-diiodoosmium(IV) tetraarylporphyrins were obtained by extremely facile synthetic routes directly from the reactions of the corresponding (carbonyl)osmium(II) complexes with CCl(4), CBr(4), and CI(4), respectively. At short reaction times, appreciable amounts of intermediates-one for each reaction-were observed by spectroscopic investigations. These intermediates were shown to be (carbonyl)(halo)(porphyrinato)osmium(III) complexes by independent preparation of an authentic (carbonyl)(bromo)(porphyrinato)osmium(III) complex, which was identical to the reaction intermediate in the reaction of CBr(4) and very similar to those of the other reactions. This provided strong evidence for the reaction mechanism, two stepwise one-electron oxidations of the metal ion. The relatively strong binding of carbon monoxide to osmium(III) is proposed to be an important factor in avoiding dimerization of the reaction intermediates.     

New deoxygenation reactions of sulfoxides,selenoxides and primary nitroalkanes to sulfides,selenides and nitriles

The title reactions are performed at room temperature for short periods using P₂I₄. The resulting products are formed in particularly high yield.     

Kinetics and mechanism of osmium(VIII) catalyzed oxidation of tellurium(IV) by cerium(IV)

The reaction is first order in substrate and catalyst and zero order in cerium(IV). The rate decreases with increasing [H⁺] as well as with increasing ionic strength. H and S have been found to be 44.8 kJ mol^–1 and 161.8 JK^–1 mol^–1 respectively. A mechanism is proposed.

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(IV). [H⁺], . , H S 44,8 ·^–1 161,8 ·^–1–1, . .

     

Kinetics and mechanism of osmium(VIII)-catalyzed oxidation of 1,4-thioxane by alkaline hexacyanoferrate(III)

The kinetics of oxidation of 1,4-thioxane (1,4-oxathiane) by alkaline K₃Fe(CN)₆ have been studied in the presence of Os^VIII as catalyst. The reaction is first order in hexacyanoferrate(III) and Os^VIII. The order in thioxane and OH^– is zero. While added salts and ethanol have a negligible effect on the oxidation rate, K₄Fe(CN)₆ retards it. On the basis of kinetic evidence, a mechanism has been proposed.