Features of the Sorptive Extraction of Osmium in Different Oxidation States with Silica Gels Chemically Modified with Mercapto and Disulfide Groups

The sorptive extraction of osmium(VIII, VI, IV) from HCl solutions with silica gels chemically modified with mercapto groups (MPS) and disulfide groups (DPDSS) was studied. The recovery of osmium(VIII) from 0.5–4 M HCl is 99 and 25% with the sorption equilibration time 5 and 20 min for MPS and DPDSS, respectively. The equilibration time for the extraction of Os(VI) with MPS is no longer than 1 min. The recovery from 0.1–4 M HCl is up to 99.9%. The recovery of osmium(VI) with DPDSS decreases from 96 and 80% when going from 0.5 M to 4 M HCl. The quantitative extraction of osmium(IV) is attained at 95°C in the presence of tin(II) chloride and the equilibration time 60 min. Without tin(II) chloride, osmium(IV) is not extracted with these sorbents. The difference in the sorption ability of chemically modified silica gels with respect to osmium in different oxidation states can be used for the extraction of osmium(VI) and osmium(IV) and their separate determination directly in the MPS phase with the use of diffuse reflectance spectrometry.     

Reactivity of dioxoosmium(VI) porphyrins toward arylhydrazine. Isolation of hydrazidoosmium and amidoosmium porphyrins

Reactions of dioxoosmium(VI) porphyrins [Os(VI)(Por)O(2)] with excess 1,1-diphenylhydrazine in tetrahydrofuran at ca. 55 degrees C for 15 min afforded bis(hydrazido(1-))osmium(IV) porphyrins [Os(IV)(Por)(NHNPh(2))(2)] (1a, Por = TPP (meso-tetraphenylporphyrinato dianion); 1b, Por = TTP (meso-tetrakis(p-tolyl)porphyrinato dianion)), hydroxo(amido)osmium(IV) porphyrins [Os(IV)(Por)(NPh(2))(OH)] (2a, Por = TPP; 2b, Por = TTP), and bis(hydrazido(2-))osmium(VI) porphyrin [Os(VI)(Por)(NNPh(2))(2)] (3c, Por = TMP (meso-tetramesitylporphyrinato dianion)). The same reaction under harsher conditions (in refluxing tetrahydrofuran for ca. 1 h) gave a nitridoosmium(VI) porphyrin, [Os(VI)(Por)(N)(OH)] (4b, Por = TTP). Oxidation of 1a,b with bromine in dichloromethane afforded bis(hydrazido(2-)) complexes [Os(VI)(TPP)(NNPh(2))(2)] (3a) and [Os(VI)(TTP)(NNPh(2))(2)] (3b), respectively. All the new osmium porphyrins were identified by (1)H NMR, IR, and UV-vis spectroscopy and mass spectrometry; the structure of 2b was determined by X-ray crystallography (Os-NPh(2) = 1.944(6) A, Os-OH = 1.952(5) A).     

Regularities in the Sorption Recovery of Osmium in Various Oxidation States (VIII, VI, and IV) on Silica Chemically Modified with Thiourea Derivatives

Regularities in the sorption recovery of osmium(VIII, VI, IV) on silica chemically modified with thiourea derivatives (N-allyl-N"-propylthiourea (ATUS), N-phenyl-N"-propylthiourea (PTUS), and N-benzoyl-N"-propylthiourea (BTUS)) were studied. The equilibrium attainment time for the solid-phase extraction of osmium(VIII) is 15, 30, and 40 min for ATUS, PTUS, and BTUS, respectively. For the solid-phase extraction of osmium(VI), equilibrium attainment time is independent of the type of the sorbent and is no more than 5 min. The recovery of osmium(IV) at 95°C and equilibration time 120 min is no higher than 5%. The quantitative recovery of osmium(IV) with silica chemically modified with thiourea derivatives is attained on long-term heating and in the presence of tin(II) chloride. Based on the regularities in the sorption recovery of osmium in different oxidation states and its interaction with thiourea in aqueous solutions with low mole ratios, it was suggested that osmium(VIII, VI) and osmium(IV) interact with thiourea and its derivatives including those covalently bonded to the silica surface via different mechanisms.     

POLYORGS as complexing sorbents for preconcentration of trace metals

Summary The main characteristics of the complexing sorbents POLYORGS are reviewed. These sorbents contain pyrazole, imidazole, amidoxime, 2-mercaptobenzothiazole, thioglycolanilide and arsenazo groups and exhibit high selectivity in respect to noble, rare-earth and heavy metals. The sorbents POLYORGS are applied for the preconcentration of these metals to be determined in ores, rocks, natural and waste waters, and industrial products. The metal determinations after preconcentration are carried out by means of different instrumental methods (e.g., AAS, XRFA, ICP-AES, NAA) either directly in the sorbent, after elution of the analytes or decomposition of the sorbent.     

Osmium phosphiniminato complexes: synthesis,protonation, structure,and redox-coupled hydrolytic scission of N-p bonds

The osmium(VI) nitrido complex TpOs(N)Cl(2) [1, Tp = hydrotris(1-pyrazolyl)borate] reacts with triarylphosphines to afford the Os(IV) phosphiniminato complexes TpOs(NPAr(3))Cl(2) [Ar = p-tolyl (tol) (2a), phenyl (2b), p-CF(3)C(6)H(4) (2c)] in nearly quantitative yield. Protonation of 2a-c with 1 equiv of HOTf in MeCN occurs at the phosphiniminato nitrogen to give [TpOs(IV)(NHPAr(3))Cl(2)]OTf (3a-c) in 68-80% yield. Solutions of 2a-c in CH(2)Cl(2) react with excess H(2)O over 1 week to form the disproportionation products 1 (28%), TpOs(III)(NHPAr(3))Cl(2) (4a-c) (60%), and OPAr(3) (35%). Treatment of solutions of 3a-c with H(2)O also affords 1, 4a-c, and OPAr(3). X-ray structures of 2b, 3b, and 4b are presented. Cyclic voltammograms of compounds 2a-c exhibit Os(V)/Os(IV) and Os(IV)/Os(III) couples at approximately 0.3 and -1 V versus Cp(2)Fe(+/0). Protonation to give 3 makes reduction easier by approximately 1.2 V, so that these compounds show Os(IV)/Os(III) and Os(III)/Os(II) couples. In the hydrolytic disproportionation of 2a-c, labeling studies using (18)O-enriched O(2) and H(2)O establish water as the source of the oxygen atom in the OPAr(3) product. The conversions are accelerated by HOTf and inhibited by NaOD. The relative rates of hydrolytic disproportionation of 2a-c vary in the order tol > Ph > p-CF(3)C(6)H(4). The data indicate that protonation of the phosphiniminato nitrogen is required for hydrolysis. The mechanism of the hydrolytic disproportionation is compared to that of the related reaction of the osmium(IV) acetonitrile complex [TpOs(NCMe)Cl(2)](+).     

Sorption Preconcentration of Platinum-Group Metals with Filled Fibrous POLYORGS Sorbents

The sorption of platinum, palladium, and rhodium with fibrous filled POLYORGS sorbents was studied depending on the concentration of hydrochloric acid and the time of contact of the solution with the sorbent in the batch mode. The equilibrium and kinetic characteristics of the sorption of platinum with the POLYORGS 17-n sorbent were determined, on the basis of these data the conditions for the dynamic preconcentration of platinum from a 1 M HCl solution were calculated. Conditions were selected for the group preconcentration of palladium, platinum, and gold in the dynamic mode and for their subsequent determination in the sorbent. It was demonstrated that rhodium can be preconcentrated with the POLYORGS 17-n sorbent in the dynamic mode in the presence of tin chloride.     

Phosphorylation of Guar Gum/Magnetite/Chitosan Nanocomposites for Uranium (VI) Sorption and Antibacterial Applications

The development of new materials is needed to address the environmental challenges of wastewater treatment. The phosphorylation of guar gum combined with its association to chitosan allows preparing an efficient sorbent for the removal of U(VI) from slightly acidic solutions. The incorporation of magnetite nanoparticles enhances solid/liquid. Functional groups are characterized by FTIR spectroscopy while textural properties are qualified by N₂ adsorption. The optimum pH is close to 4 (deprotonation of amine and phosphonate groups). Uptake kinetics are fast (60 min of contact), fitted by a pseudo-first order rate equation. Maximum sorption capacities are close to 1.28 and 1.16 mmol U g⁻¹ (non-magnetic and magnetic, respectively), while the sorption isotherms are fitted by Langmuir equation. Uranyl desorption (using 0.2 M HCl solutions) is achieved within 20–30 min; the sorbents can be recycled for at least five cycles (5–6% loss in sorption performance, complete desorption). In multi-component solutions, the sorbents show marked preference for U(VI) and Nd(III) over alkali-earth metals and Si(IV). The zone of exclusion method shows that magnetic sorbent has antibacterial effects against both Gram+ and Gram- bacteria, contrary to non-magnetic material (only Gram+ bacteria). The magnetic composite is highly promising as antimicrobial support and for recovery of valuable metals.     

Preparation,properties and analytical application of silica with chemically grafted hydroxamic acid groups

The synthesis of silica chemically modified with propanohydroxamic acid groups and salicylhydroxamic acid is described. Sorption of 13 metal ions is studied as a function of pH. The composition of the sorbed complexes is determined and the apparent stability constants of the complexes in the sorbent phase are calculated. A correlation between the stabilities of the complexes in the sorbent phase and in aqueous solution is observed in some cases. Some analytical applications of the sorbents are demonstrated: trace amounts of elements can be concentrated from large volumes; molybdenum(VI) and zirconium(IV) can be separated from 10⁴-fold amounts of accompanying elements, and vanadium(V) can be determined in the sorbent phase by using diffuse reflection and photoacoustic spectrometric techniques.     

Removal of heavy metal ions from aqueous solutions using low-cost sorbents obtained from ash

This study’s main objective was the development of effective low-cost sorbents for the removal of heavy metal ions from aqueous solutions. The influence of different factors on the sorption capacity of ash and modified ash as low-cost sorbents obtained by different methods was investigated. The synthesis of new ash-based materials was carried out at ambient temperature (20°C), 70°C, and 90°C, respectively, in an alkaline medium with NaOH concentrations of 2 M and 5 M, respectively, corresponding to a mixture with solid/liquid ratios of 1: 3 and 1: 5, respectively. The prepared materials (sorbents) were characterised by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction, and BET surface measurement. Adsorption isotherms were determined using the batch equilibrium method. The results showed that these types of new materials displayed a good capacity to remove copper, nickel, and lead ions (29.97 mg of Cu²⁺ per g of sorbent, 303 mg of Ni²⁺ per g of sorbent, and 1111 mg of Pb²⁺ per g of sorbent) from aqueous solutions. The modified materials were prepared using an alkaline attack (a recognised method used in previous studies), but Romanian ash from a thermal power plant was studied for the above purpose for the first time. Hence, the factors which affect the sorption capacity of the prepared low-cost sorbents were determined and their behaviour was explained, taking into account the composition and structure of the new materials.     

Binuclear (salen)osmium phosphinidine and phosphiniminato complexes

The preparation of a number of binuclear (salen)osmium phosphinidine and phosphiniminato complexes using various strategies are described. Treatment of [Os(VI)(N)(L(1))(sol)](X) (sol = H(2)O or MeOH) with PPh(3) affords an osmium(IV) phosphinidine complex [Os(IV){N(H)PPh(3)}(L(1))(OMe)](X) (X = PF(6)1a, ClO(4)1b). If the reaction is carried out in CH(2)Cl(2) in the presence of excess pyrazine the osmium(III) phosphinidine species [Os(III){N(H)PPh(3)}(L(1))(pz)](PF(6)) 2 can be generated. On the other hand, if the reaction is carried out in CH(2)Cl(2) in the presence of a small amount of H(2)O, a μ-oxo osmium(IV) phosphinidine complex is obtained, [(L(1)){PPh(3)N(H)}Os(IV)-O-Os(IV){N(H)PPh(3)}(L(1))](PF(6))(2)3. Furthermore, if the reaction of [Os(VI)(N)(L(1))(OH(2))]PF(6) with PPh(3) is done in the presence of 2, the μ-pyrazine species, [(L(1)){PPh(3)N(H)}Os(III)-pz-Os(III){N(H)PPh(3)}(L(1))](PF(6))(2)4 can be isolated. Novel binuclear osmium(IV) complexes can be prepared by the use of a diphosphine ligand to attack two Os(VI)≡N. Reaction of [Os(VI)(N)(L(1))(OH(2))](PF(6)) with PPh(2)-C≡C-PPh(2) or PPh(2)-(CH(2))(3)-PPh(2) in MeOH affords the binuclear complexes [(MeO)(L(1))Os(IV){N(H)PPh(2)-R-PPh(2)N(H)}Os(IV)(L(1))(OMe)](PF(6))(2) (R = C≡C 5, (CH(2))(3)6). Reaction of [Os(VI)(N)(L(2))Cl] with PPh(2)FcPPh(2) generates a novel trimetallic complex, [Cl(L(2))Os(IV){NPPh(2)-Fc-PPh(2)N}Os(IV)(L(2))Cl] 7. The structures of 1b, 2, 3, 4, 5 and 7 have been determined by X-ray crystallography.     

Chemistry of osmium in N2P2Br2 coordination sphere: Synthesis,structure and reactivities

A family of three mixed-ligand osmium complexes of type [Os(PPh₃)₂(N-N)Br₂], where N-N=2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy) and 1,10-phenanthroline (phen), have been synthesized and characterized. The complexes are diamagnetic (low-spin d⁶, S=0) and in dichloromethane solution they show intense MLCT transitions in the visible region. The two bromide ligands have been replaced from the coordination sphere of [Os(PPh₃)₂(phen)Br₂] under mild conditions by a series of anionic ligands L (where L=quinolin-8-olate (q), picolinate (pic), oxalate (Hox) and 1-nitroso-2-naphtholate (nn)) to afford complexes of type [Os(PPh₃)₂(phen)(L)]⁺, which have been isolated and characterized as the perchlorate salt. The structure of the [Os(PPh₃)₂(phen)(pic)]ClO₄ complex has been determined by X-ray crystallography. The PPh₃ ligands occupy trans positions and the picolinate anion is coordinated to osmium as a bidentate N,O-donor forming a five-membered chelate ring. The [Os(PPh₃)₂(phen)(L)]⁺ complexes are diamagnetic and show multiple MLCT transitions in the visible region. The [Os(PPh₃)₂(N-N)Br₂] complexes show an osmium(II)–osmium(III) oxidation (−0.02 to 0.12 V vs. SCE) followed by an osmium(III)–osmium(IV) oxidation (1.31 to 1.43 V vs. SCE). The [Os(PPh₃)₂(phen)(L)]⁺ complexes display the osmium (II)–osmium (III) oxidation (0.26 to 0.84 V vs. SCE) and one reduction of phen (−1.50 to −1.79 V vs. SCE). The osmium (III)–osmium (IV) oxidation has been observed only for the L=q and L=Hox complexes at 1.38 V vs. SCE and 1.42 V vs. SCE respectively. The osmium(III) species, viz. [Os^III(PPh₃)₂(N-N)Br₂]⁺ and [Os^III(PPh₃)₂(phen)(L)]²⁺, have been generated both chemically and electrochemically and characterized in solution by electronic spectroscopy and cyclic voltammetry.     

A Study on Stripping Voltammetric Determination of Osmium(IV) at a Carbon Paste Electrode Modified In Situ with Cationic Surfactants

This article deals with the development of a method for the determination of osmium at a carbon paste electrode (CPE) modified with cationic surfactants of the quaternary ammonium salt type; namely, cetyltrimethylammonium bromide (CTAB) and 1‐(ethoxycarbonyl)‐pentadecyltrimethyl‐ammonium bromide (Septonex); both being added in situ and serving for preconcentration of osmium via its hexachloroosmate(IV) anion. The proper electrochemical detection was performed by cathodic scanning in the differential pulse voltammetric mode. Optimization studies concerning important experimental parameters also included a specially performed potentiometric titration, helping to define the actual stoichiometry for the ion‐pairing process, the main principle and driving force of the accumulation step. In a chloride/acetate buffer based supporting medium and with Septonex as the modifier of choice, the reduction signal for osmium was found to be proportional to the Os(IV) concentration in a range from 5×10^?9 to 5×10^?7 mol L^?1 with a limit of detection close to 5×10^?9 mol L^?1 (with preconcentration for 60 s). The method capable to determine Os(IV) in the presence of both Pt(IV) and Ir(III) was tested on model solutions as well as with real sample of industrial waste water (spiked with the analyte); both yielding the recovery rates within 88–99%.     

Synthesis and properties of oxo-carboxylato- and dioxo-bridged diosmium complexes of tris(2-pyridylmethyl)amine

A series of oxo-bridged diosmium complexes with tpa ligand (tpa = tris(2-pyridylmethyl)amine) are synthesized. The hydrolytic reaction of the mononuclear osmium complex [Os(III)Cl(2)(tpa)]PF(6) in aqueous solution containing a sodium carboxylate yields a μ-oxo-μ-carboxylato-diosmium(III) complex, [Os(III)(2)(μ-O)(μ-RCOO)(tpa)(2)](PF(6))(3) (R = C(3)H(7) (1), CH(3) (2), or C(6)H(5) (3)). One-electron oxidation of 1 with (NH(4))(2)Ce(IV)(NO(3))(6) gives a mixed-valent [Os(III)Os(IV)(μ-O)(μ-C(3)H(7)COO)(tpa)(2)](PF(6))(4) complex (4). A mixed-valent di-μ-oxo-diosmium complex, [Os(III)Os(IV)(μ-O)(2)(tpa)(2)](PF(6))(3) (5), is also synthesized from 1 in an aerobic alkaline solution (pH 13.5). All the complexes exhibit strong absorption bands in a visible-near-infrared region based on interactions of the osmium dπ and oxygen pπ orbitals of the Os-O-Os moiety. The X-ray crystallographic analysis of 1, 3, and 4 shows that the osmium centers take a pseudo-octahedral geometry in the μ-oxo-μ-carboxylato-diosmium core. The mixed-valent osmium(III)osmium(IV) complex 4 has a shorter osmium-oxo bond and a larger osmium-oxo-osmium angle as compared with those of the diosmium(III) complex 1 having the same bridging carboxylate. Crystal structure of 5 reveals that the two osmium ions are bridged by two oxo groups to give an Os(2)(μ-O)(2) core with the significantly short osmium-osmium distance (2.51784(7) ?), which is indicative of a direct osmium-osmium bond formation with the bond order of 1.5 (σ(2)π(2)δ(2)δ*(2)π*(1) configuration). In the electrochemical studies, the μ-oxo-μ-carboxylato-diosmium(III) complexes exhibit two reversible Os(III)Os(III)/Os(III)Os(IV) and Os(III)Os(IV)/Os(IV)Os(IV) oxidation couples and one irreversible redox wave for the Os(III)Os(III)/Os(II)Os(III) couple in CH(3)CN. The irreversible reductive process becomes reversible in CH(3)CN/H(2)O (1:1 Britton-Robinson buffer; pH 5-11), where the {1H(+)/2e(-)} transfer process is indicated by the plot of the redox potentials against the pH values of the solution of 1. Thus, the μ-oxo-μ-butyrato-diosmium(III) center undergoes proton-coupled electron transfer to yield a μ-hydroxo-μ-butyrato-diosmisum(II) species. The di(μ-oxo) complex 5 exhibits one reversible Os(III)Os(IV)/Os(IV)Os(IV) oxidation process and one reversible Os(III)Os(IV)/Os(III)Os(III) reduction process in CH(3)CN. The comproportionation constants K(com) of the Os(III)Os(IV) states for the present diosmium complexes are on the order of 10(19). The values are significantly larger when compared with those of similar oxo-bridged dimetal complexes of ruthenium and rhenium.     

Blue Osmium(IV) Sulfite Complex: Synthesis and Study

Blue osmium(IV) sulfite complex Na₄[Os₂(-O)₂(SO₃)₄(H₂O)₄] · 4.5 H₂O was synthesized via the reaction of aqueous solutions containing OsO₄ and equimolar amount of Na₂SO₃ and H₂SO₄ at 50°C and its composition and structure were determined by elemental analysis, X-ray electronic and IR spectroscopies, and thermogravimetric analysis. The compound is X-ray amorphous, insoluble in water but soluble in hydrochloric and sulfuric acids. The electrochemical methods (cyclic voltammetry and potential-controlled coulometry) indicate the complex polymerization in solutions. Under continuous electrolysis at high negative potentials (E _r = –0.10 V), the product under study is depolymerized and the monomeric Os(II) complexes are formed. At a high positive potential (E ₀ = 1.00 V), Os(VI) is formed that disproportionates into Os(IV) and Os(VIII).     

Spectrophotometric determination of osmium with phthalimide dithiosemicarbazone by means of complex formation and catalytic reactions

Phthalimide dithiosemicarbazone forms a 1:1 complex with osmium at pH 3.3–4.5 (?₄₅₀ = 1.3 · 10⁴ l mol^?1 cm^?1 ) which is applied to the photometric determination of osmium; Beer's law is obeyed for the range 1–12 μg Os ml^?1. The oxidation of the reagent with cerium(IV) is catalyzed by osmium(VIII), and this reaction allows a more sensitive procedure for the determination of osmium; the calibration curve is linear over the range 0.05–0.4 μg Os ml^?1. The interferences in both procedures are described.     

Multielement Preconcentration and Removal of Trace Metals by Solid-Phase Extraction

ABSTRACT

The solid phase extraction of trace amounts of some metal ions from their mixtures using cation exchanger Dowex 50Wx4, cellulose sorbent with phosphonic acid groups Cellex P, chelating resin Chelex 100 and SIO₂-TPP sorbent which contains porphyrin ligand covalently attached to aminopropyl silica gel was investigated. With respect to multielement preconcentration Cellex P and Chelex 100 seem to be the best sorbents; the recovery test for Al, Be, Cd, Ni, Pb and Zn were > 90%. Additionally, Cellex P appeared to be suitable for enrichment of Co and Mn. Silica-TPP sorbent could be applied as a selective collector for Mo(VI) and V(IV).     

Sorbents based on calix[4]arenes for extraction of technetium(vii) from acidic and alkaline media

Sorption of Tc^VII from solutions of various compositions with new sorbents prepared by the noncovalent immobilization of (thia)calix[4]arenes on the Amberlite XAD-7™ support was studied. The sorbents studied efficiently extract technetium(vii) from both acidic and alkaline media. The sorption capacity of the sorbent with thiacalix[4]arene groups is superior to that of the sorbents with calix[4]arene groups and several times higher than that of the sorbents previously proposed for the sorption of Tc^VII. Technetium(vii) is sorbed by this sorbent as 1: 1 and 1: 2 thiacalix[4]arene—NH₄TcO₄ and 1: 1 and 1: 2 thiacalix[4]arene—NaTcO₄ complexes.     

Photometric determination of osmium with thiourea after extraction of the tetroxide

A general method for the determination of 5–1000 γ of osmium involves extraction of osmium tetroxide with chloroform or carbon tetrachloride, followed by shaking the organic solvent with a sulfuric acid solution, of thiourea to form red Os(NH₂CSNH₂)₆⁺³, whose color intensity is measured photometrically. A sharp separation of osmium from ruthenium can be obtained by reducing Os(VIII) and Ru(VIII) with ferrous sulfate and then oxidizing Os(IV) to Os(VIII) with nitric acid; ruthenium remains reduced and is not extracted by chloroform or carbon tetrachloride.     

Sorption of cadmium ions from aqueous solutions onto nanoporous modified carbon sorbents

Physicochemical properties of nanoporous modified carbon sorbents and sorption of cadmium ions (0.1–20 mg L^?1) onto them from nitrate solutions at pH 5–7 were studied. The acid-base nature of functional oxygen-containing groups on the carbon surface of the sorbents was determined. The ability to sorb cadmium ions depends on the kind of chemical modification of the sorbent surface.     

乙腈溶液中锇氮化合物电化学诱导桥氮偶联过程的原位FTIR反射光谱研究(英)

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