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Approaches to the synthesis of trinuclear ReFePt clusters, their behaviour in solution and pathways of their redox-induced reactions are studied.

The redox properties of levulinic acid (LA) were studied by electrochemical methods in acetonitrile, a mixture of acetonitrile with water, ethanol, acetone, and dimethyl sulfoxide. It was shown that the irreversible two-electron reduction of LA under the studied conditions leads to the formation of γ-valerolactone. This reduction potential depends on the solvent and shifted anodically by following order: dimethyl sulfoxide

The binuclear μ-vinylidene complexes containing an isocyanide ligand (1-(isocyanomethylsulfonyl)-4-methylbenzene) Cp(CO)2RePt(μ-C=CHPh)(TosMIC)(L) [L = PPh3 (1), P(OPri)3 (2)] were synthesized for the first time. The approach afforded 1 and 2 based on the substitution reactions of a platinum bound carbonyl group in Cp(CO)2RePt(μ-C=CHPh)(CO)(L) [L = PPh3 (1a), P(OPri)3 (2a)] upon addition of 1-(isocyanomethylsulfonyl)-4-methylbenzene. The complexes 1 and 2 were characterized by IR and NMR spectroscopy. Their redox properties were studied

The μ-phenylvinylidene complexes Cp(CO)2RePt(μ-C=CHPh)(PPh2H)(L) [L = PPh3 (1), P(OPri)3 (2)] were synthesized for the first time. Their IR, NMR spectroscopic and redox properties were studied. Based on IR, NMR spectroscopic data their molecular structures were proposed. The pathways of redox-reactions of the complexes were determined

The new σ-alkynyl iron(II) complex Cp(CO)2Fe-C≡C-(2-C4H3S) was synthesized with application of several known approaches based on the transition metal (Pd/Cu–, Au–, Cu– and Pd–) catalyzed Fe–C coupling reactions of 2-ethynylthiophene or 2-[(trimethylsilyl)ethynyl]thiophene with cyclopentadienyliron dicarbonyl iodide. The yield of the complex in these reactions was found to strongly depend on the catalyst used. The conditions, catalysts, and reagents that provide the highest yields of the desired 2-thienylethynyl iron complex were determined. The complex was characterized by IR, 1H and 13C NMR spectroscopy. The molecular structure of Cp(CO)2Fe–C≡C-(2-C4H3S) established by X-ray diffraction analysis exhibits a three-leg piano stool geometry. The redox properties of the new complex were studied.

A series of trinuclear μ

The chemical oxidation of the cluster CpReFePt(μ3-C=CHPh)(CO)5(dppe) (Cp = η5-C5H5, dppe = η2- Ph2P(CH2)2PPh2) resulted in a radical cation [CpReFePt(μ3-C=CHPh)(CO)5(dppe)]+• that is sufficiently stable only at low temperature. An electronic structure of the radical cation was studied by EPR and following parameters were obtained by comparison of the experimental and model spectrum: gx = 2.070 gy = 2.0295 gz = 1.997; Ax(31P) = 17 Ay(31P) = 49 Az(31P) = 35 (Gs);Ax(195Pt) = 62 Ay(195Pt) = 45 Az(195Pt) = 105 (Gs). An unpaired electron is seen to be mainly concentrated on the iron atom (85-90%) and partially on the platinum atom (10-15%). Further transformation of the radical cation led to the formation of the binuclear complex Cp(CO)2RePt(μ-C=CHPh)(dppe) and the Fe-carbonyl fragment

The redox properties of mononuclear dicarbonyl and carbonylphosphine rhodium (I) complexes (CO)(L)Rh(RC(O)CHC(O)R’) with chelate β-diketonate ligands (L = CO, PPh3; R, R’ = Me, Ph; CF3, C4H3S) were studied by electrochemical methods at platinum, glassed carbon and dropping mercury electrodes in acetonitrile. Schemes of their redox reactions were established

The known Rh(2-Me-8-Oxq)(CO)2 complex (1) was prepared through treatment of dicarbonyl(acetylacetonate)rhodium (I) with 2-methyl-8-hydroxyquinoline for the first time. The reactions of 1 with triphenylphosphine and triphenylphosphite result in complexes Rh(2-Me-8-Oxq)(PPh3)(CO) (2) and Rh(2-Me-8-Oxq)[P(OPh)3](CO) (3) that were characterized by IR and NMR spectroscopy. The structures of complexes 2 and 3 were determined by single-crystal X-ray diffraction analysis. The complexes show the 2-methyl-8-quinolinolato ligand in the expected coordination mode with a slightly disordered square planar geometry at the rhodium center. In the crystal, molecules of Rh(2-Ме-8-Oxq)(CO)(PPh3) (2) form centrosymmetric dimers due to π-stacking interactions. No intermolecular contacts are observed in the crystal of 3. The UV spectroscopic and electrochemical properties of complexes 1–3 were studied. Their electronic spectra in CH3CN show three quinoline-centered absorptions. The electrochemical study revealed that the oxidation of the complexes 1–3 is two-electron and leads to the formation of dication Rh (III) species while their reduction gives radical anions, which undergoes rapid decomposition.

The novel heterobinuclear μ-vinylidene complex [Cp(CO)2Re(μ-C=CHPh)Pt(PPh3)(CO)] (1) was isolated from the reaction mixture of [Cp(CO)2Re(μ-C=CHPh)Fe(CO)4] and Pt(PPh3)4 for the first time. Alternative high-yield synthetic approaches to 1 were developed including the reactions of [Cp(CO)2Re(μ-C=CHPh)Pt(PPh3)2] (2) with Co2(CO)8 and Rh(acac)(CO)2. The complex was characterized by IR and 1H, 13C and 31P NMR spectroscopy, a molecular structure of 1 was determined by X-ray diffraction analysis. The electrochemical behavior of the new complex was studied by cyclic voltammetry at platinum or glassed carbon electrodes and by dc polarography at a dropping mercury electrode.

Redox-induced transformations of bi-Cp(CO)2RePd(μ-C CHPh)(PPh3)2 (2), Cp(CO)2RePd(μ-C CHPh)(P-P) [P-P = η2-Ph2P(CH2)2PPh2 (dppe) (3), η2-Ph2P(CH2)3PPh2 (dppp) (4)], Cp(CO)2ReFe(μ-C CHPh)(CO)4 (5) and trinuclear Cp(CO)2ReFe2(μ3-C CHPh)(CO)6 (6), CpReFePd(µ3-C CHPh)(CO)5(P-P) [P-P = dppe (7), dppp (8)] heterometallic vinylidene complexes derived from Cp(CO)2Re C CHPh (1) were investigated by electrochemical methods. The oxidation processes of clusters 7 and 8 were studied by EPR spectroscopy. The electrochemical properties of clusters 7 and 8 were shown to depend on the nature of the chelate diphosphine ligand at the palladium center in contrast to complexes 3 and 4. The oxidation of complexes 2–4 was found to result in the Re-Pd, Pd-C bond cleavage and formation of rhenium complex 1 and Pd-containing fragments. The oxidation of 7 and 8 resulted in the formation of the radical cations 7+ and 8+ , which sequentially transformed into a number of intermediate products: Cp(CO)2RePd(μ-C CHPh)(P-P), [Fe(CO)3]+ , [CpReFe2(µ3-C CHPh)(CO)6]+ and others. The final products of their oxidation in both cases were triangular clusters (CO)8Fe2Pd(P-P) [P-P = dppe (9), dppp (10)] and rhenium complex 1. The molecular structure of cluster 7 was established by X-ray diffraction analysis.

The advantage of capillary electrophoresis was demonstrated for studying a complicated system owing to the dependence of direction and velocity of the electrophoretic movement on the charge of complex species. The stability constants of copper(II) complexes with ions of succinic acid were determined by capillary electrophoresis, including the 1 : 2 metal to ligand complexes which are rarely mentioned. The measurements were carried out at 25 °C and ionic strength of 0.1, obtained by mixing the solutions of succinic acid and lithium hydroxide up to pH 4.2–6.2. It was shown that while pH was more than 4.5 the zone of copper(II) complexes with succinate moves as an anion. It is impossible to treat this fact using only the complexes with a metal-ligand ratio of 1 : 1 (CuL0, CuHL+). The following values of stability constants were obtained: log β(CuL) = 2.89 ± 0.02, log β(CuHL+) = 5.4 ± 0.5, log β(CuL22−) = 3.88 ± 0.05, log β(CuHL2−) = 7.2 ± 0.3.

A strategy for non-target analysis of samples with unknown composition by capillary electrophoresis (CE) with ultraviolet (UV) detection is suggested. The strategy is based on the preliminary identification of analytes and further optimization of the conditions for their separation using the developed computational tool set ElphoSeparation. It is shown that, in order to record electrophoretic peaks with the mobilities from the maximum to minimum possible values, the positive and negative voltage polarity and hydrodynamic pressure should be used. To choose the optimal separation conditions, dynamic maps of electrophoretic separation (DMES) are suggested. DMES is a bar chart with theoretical resolutions of adjacent peaks presented in ascending order of the migration time. The resolution is calculated as the division of the difference of the effective electrophoretic mobilities of adjacent analytes by their average peak width in terms of electrophoretic mobility. The suggested strategy is tested by the example of the analysis of herbal medicine (Holosas) on the basis of rose hips. The approach should be used to analyze samples with not very complex composition, such as environmental water and precipitation samples, process liquors, some vegetable extracts, biological fluids, food, and other samples for the determination of widespread compounds capable of forming ionic species. For samples with complex composition, the approach used together with other techniques may produce advantageous information due to specificity of the method, particularly it can be useful for determination of compounds suffering from low volatility or thermal stability, and for analysis of samples with difficult matrices. Graphical Abstract The scheme of performing the non-target ionic analysis by capillary electrophoresis with ultraviolet detection.

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала. The influence of analyte concentration when compared with the concentration of a charged ligand in background electrolyte (BGE) on the measured values of electrophoretic mobilities and stability constants (association, binding or formation constants) is studied using capillary electrophoresis (CE) and a dynamic mathematical simulator of CE. The study is performed using labile complexes (with fast kinetics) of iron (III) and 5-sulfosalicylate ions (ISC) as an example. It is shown that because the ligand concentration in the analyte zone is not equal to that in BGE, considerable changes in the migration times and electrophoretic mobilities are observed, resulting in systematic errors in the stability constant values. Of crucial significance is the slope of the dependence of the electrophoretic mobility decrease on the ligand equilibrium concentration.Without prior information on this dependence to accurately evaluate the stability constants for similar systems, the total ligand concentration must be at least >50–100 times higher than the total concentration of analyte. Experimental ISC peak fronting and the difference between the direction of the experimental pH dependence of the electrophoretic mobility decrease and the mathematical simulation allow assuming the presence of capillary wall interaction.

The redox properties of new binuclear μ-vinylidene complexes Cp(CO)2RePt(μ-C = C2HPh)LL′ [L = СO, L′ = PPh3 (1); L = СO, L′ = P(OPr)3 (2); L = L′ = PPh3 (3); L = L′ = P(OPr)3 (4)] were studied by electrochemical methods at a platinum, a glassed carbon and a dropping mercury electrodes in acetonitrile solutions. It was established that one-electron oxidation of 3 and 4 results in a cleavage of the Re-Pt and Pt-C1 bonds affording vinylidene complex Cp(CO)2RePt = C = CHPh and [PtLL′] fragments. In contrast to complexes 3 and 4, one-electron oxidation of 1 and 2 is reversible, indicating the greater electrochemical stability of lasts relative to 3 and 4.

It was shown that the early suggested method for the determination of organic acids (oxalic, tartaric, citric, malic, lactic, succinic, acetic) in wine by capillary electrophoresis technique can be used for the determination of organic acids into fruit and vegetable juices . Generally, the studied juices are found to contain citric, malic and lactic acids. The content of organic acids in the analyzing samples does not exceed the established standards of SanPiN 2.3.2.1293-03 for the food additives. The accuracy of the results of analysis was confirmed by the added–found method.

Reactions of Cp(CO)2Re C CHPh with Pt[P(OR)3]4 (R = Pri, Et, Ph) gave binuclear μ-vinylidene complexes Cp(CO)2RePt(μ-C CHPh)[P(OR)3]2. Treatment of the previously synthesized Cp(CO)2Re(μ-C CHPh)Pt(PPh3)2 with triisopropylphosphite or triethylphosphite resulted in a stepwise substitution of PPh3 ligands, leading to the disubstituted Cp(CO)2RePt(μ-C CHPh)[P(OR)3]2 and monosubstituted Cp(CO)2RePt(μ-C CHPh)[P(OR)3](PPh3) (R = Pri or Et) species, while no triphenylphosphine ligand substitution in the reaction with P(OPh)3 occurs at all. The monosubstituted Cp(CO)2RePt(μ-C CHPh)[P(OR)3](PPh3) (R = Pri, Et, Ph) species were also obtained by reacting Cp(CO)2Re C CHPh with mixed-ligand complexes Pt(PPh3)3L (L = P(OPri)3, P(OEt)3, P(OPh)3). Reactions of Cp(CO)2RePt(μ-C CHPh)LL′ (L = L′ = P(OPri)3, P(OEt)3, P(OPh)3; L = P(OPri)3, P(OEt)3, P(OPh)3, L′ = PPh3) with Co2(CO)9 yield tricarbonyl vinylidene species Cp(CO)2RePt(μ-C CHPh)[P(OR)3](CO) (R = Pri, Et, Ph). The obtained compounds were characterized by IR and 1H, 13C, 31P NMR spectroscopy. The molecular structures of Cp(CO)2RePt(μ-C CHPh)[P(OPri)3]2, Cp(CO)2RePt(μ-C CHPh)[P(OPri)3](PPh3) and Cp(CO)2RePt(μ-C CHPh)[P(OPri)3](CO) were determined by X-ray diffraction study. The redox properties of the new complexes and their reactions of chemical oxidation were studied.

A method is developed for the determination of iron(III) and copper(II) in cognacs by capillary electrophoresis (CE) with diode array detection with limits of detection 0.06 and 0.6 mg/L, respectively. Foreign substances present in cognac do not interfere with the determination. The accuracy of the results of analysis was confirmed by the added-found method. The method was applied to the analysis of seven cognac samples. The data obtained by CE are in a good agreement with the results of inductively coupled plasma mass spectrometry.

The conditions of the sorption preconcentration of phenols from samples of natural and potable waters in Diapak P concentrator cartridges filled with super-cross-linked polystyrene are optimized. Countercurrent desorption with acetonitrile or methanol ensures the elimination the step of organic solvent evaporation. The observed reduction of the sorption of humic and fulvic acids (HFA) on the addition of sodium sulfite to the samples of natural and potable waters prior to their processing probably relates to the change of pH. The preconcentration of phenols from natural and potable waters at pH 6–8 substantially reduces the sorption of HFA. The method is used to determine phenols in samples of tap water and water from the Yenisei river by the added-found method.

The reaction of [Cp(CO) 2 Re C CHPh] ( 1 ) with [Pd(PPh 3 ) 4 ] followed by the treatment of resulting [Cp(CO) 2 RePd(μ-C CHPh)(PPh 3 ) 2 ] ( 2 ) with diphosphines (dppe, dppp) gave new complexes [Cp(CO) 2 RePd(μ-C CHPh)(dppe)] ( 3 ) and [Cp(CO) 2 RePd(μ-C CHPh)(dppp)] ( 4 ). Treatment of the synthesized complexes with [Fe 2 (CO) 9 ] led to mixtures of [Cp(CO) 2 ReFe(μ-C CHPh)(CO) 4 ] ( 5 ), [(dppe)PdFe 2 (CO) 8 ] ( 6 ), [CpReFe 2 (μ 3 -C CHPh)(CO) 8 ] ( 7 ), [CpReFePd(μ 3 -C CHPh)(CO) 5 (dppe)] ( 8 ) and of 5 , [(dppp)PdFe 2 (CO) 8 ] ( 9 ), [CpReFePd(μ 3 -C CHPh)(CO) 5 (dppp)] ( 10 ), respectively. The main products of both reactions were trinuclear μ 3 -vinylidene clusters 8 and 10 . Reactions of the trinuclear μ 3 -vinylidene ReFePd clusters 8 and 10 with Fe 2 (CO) 9 were also studied. New complexes were characterized by IR, 1 H, 13 C, 31 P NMR spectroscopy and cyclic voltammetry. The structure of [CpReFe 2 (μ 3 -C CHPh)(CO) 8 ] was determined by single-crystal X-ray diffraction.

The interaction between Cp(CO)2Re C CHPh (1) and CuCl results in the new heterometallic μ-vinylidene complex [Cp(CO)2ReCu(μ2-C CHPh)(μ2-Cl)]2 (2) characterized earlier by IR and 1H, 13C NMR spectra. The molecular structure of compound 2 has been determined by X-ray diffraction analysis, revealing a dimer structure with two binuclear fragments linked to each other by asymmetric chloride bridges. The electrochemical behavior of 2 in acetonitrile was studied by cyclic voltammetry at a Pt-electrode.

The electrochemical reactions of carbonyl cluster compounds M3(CO)12 (M = Fe, Ru, Os) were compared with those of [Fe5C(CO)14]2− and [Fe6C(CO)16]2− in different aprotic solvents. The stability of electrochemically generated products of these clusters in the studied solvents was shown to grow in the following order: tetrahydrofuran < acetone < dichloromethane < acetonitrile.

We studied system peaks present in the electropherograms obtained in the separation of anions by capillary electrophoresis with indirect spectrophotometric detection and cathode electroosmotic flow (EOF) with a chromate background electrolyte. The system peaks correspond to the zones with changed concentration of the background electrolyte; they formed when the zones of each analyte passed through the outlet of the capillary and then moved towards the EOF detector. It has been revealed that the height and area of the system peaks linearly depends on the concentration of the corresponding anion and the areas of the system peaks can achieve 10% of the anion peak area. An algorithm has been proposed for the determination of the optimal conditions for anion separation using hydrodynamic pressure for the regulation of the EOF flow rate. This algorithm prevents the overlapping of the anion and system peaks.

A version of capillary electrophoresis with indirect spectrophotometric detection and the hydrodynamic suppression of electroosmotic flow is studied. It is shown that, to improve the reliability of ion identification, one should calculate electrophoretic mobilities of ions or migration times corrected with regard to the electroosmotic flow rate. Correlations between electrophoretic peak areas of ions and their electrophoretic mobilities are derived. In the studied version of capillary electrophoresis, the accuracy of measuring anion concentrations can be improved using the internal standard method.

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала. We developed a procedure for determining manganese(II) in wines by stripping voltammetry on a graphite electrode as a poorly soluble compound. The detection limit of manganese(II) is 50 µg/L. The dependence of the analytical signal of manganese(II) on its concentration in solution is linear in the range 0.1–3 mg/L. It is demonstrated that the results of the stripping voltammetric determination of manganese(II) in wines agree with the data obtained by inductively coupled plasma mass spectrometry and EPR spectrom etry.

The electrochemical behavior of the heteronuclear dimeric vinylidene complex [Cp(CO)2MnCu(μ-C=CHPh)(μ-Cl)]2 (I) is studied using polarography, cyclic voltammetry, and controlled-potential electrolysis on mercury and platinum electrodes in acetonitrile. The dimer is reduced in two two-electron stages: at the first stage, metal-halogen bonds are broken and binuclear monomers [Cp(CO)2MnCu(μ-C=CHPh)(Cl)]− are formed; at the second stage, mononuclear manganese complexes Cp(CO)2Mn=C=CHPh, metallic copper, and chloride ions are formed. The two-electron oxidation of dimer [Cp(CO)2MnCu(μ-C=CHPh)(μ-Cl)]2 also results in the formation of binuclear monomers, which decompose to complex Cp(CO)2Mn=C=CHPh, Cu2+ ions, and Cl− ions.

Schemes of redox transformations were proposed for osmium carbonylhydride clusters: trinuclear (μ-H)Os3(μ-CR = CHR')(CO)10 (R = R' = H, Ph; R = H, R' = Ph), (μ-H)2Os3(μ3-L)(CO)9 (L = C = CHPh, CH≡CPh), tetranuclear CpMnOs3 (μ-CH = CHPh)(μ-H)(μ-CO)(CO)11, and trinuclear Os3(μ3-C = CHPh)(CO)9. Two-electron reduction of the trinuclear clusters results in elimination of the unsaturated ligand with preservation of the metal framework.

Reduction of a series of palladium-containing complexes with MnPd, Fe2Pd, and Fe3Pd skeletons was studied by classical polarography, cyclic voltammetry, and controlled-potential electrolysis in acetonitrile. The electrochemical behavior of these complexes was compared to that of relared platinum complexes.

The reaction between [Fe2(CO)9] and [Cp(CO)2MnPt(μ-C CHPh)(dppp)] (1), where dppp is Ph2P(CH2)3PPh2, proceeds stepwise, initially through transmetalation of the bridging vinylidene ligand, i.e. with replacement of the [Mn(CO)2Cp] fragment by the [Fe(CO)4] group, to produce the novel binuclear μ-vinylidene complex [(dppp)PtFe(μ-C CHPh)(CO)4] (2), which reacts further with [Fe2(CO)9] to yield the tetranuclear cluster [(dppp)PtFe3(μ4-C CHPh)(CO)9] (3) and the trinuclear complex [(dppp)PtFe2(CO)8] (4). The IR and1H,13C and31P NMR data for the new complexes are reported and discussed.

The system peaks that often appear on electropherograms in anion separation by CE with indirect spectrophotometric detection, negative voltage polarity and cathodic EOF are studied. The system peaks are shown to correspond to the zones with the changed concentration of the BGE constituents; they appear while the zone of each analyte anion passes through the outlet end of the capillary and are transported to the detector by EOF. An equation is suggested for predicting migration times of the system peaks with an error of 1%. The ratios of the system peak area to the analyte peak area are found to amount to 20%. It is shown that it is possible to avoid overlapping of the system peaks and analyte peaks by controlling the EOF velocity owing to hydrodynamic pressure. Using the mathematical simulation of CE shows that the system peaks and baseline shift can result from changing the transference numbers of the BGE ions and analyte ions at the capillary edge. The cases when the system peak may be incorrectly identified as the peak of analyte ion are considered. In order to avoid such errors, some practical recommendations are given.

Comparison of the results of the electrochemical reduction of trinuclear osmium carbonyl halides with linear structure, Os3(CO)12X2, and nonlinear structure, Os3(CO)10(μ-X)2 (X=I, Br, and Cl) with mononuclear carbonyl halides of transition metals indicates covalent nature of the metal-halogen bonds in these compounds. Chemical dissociation does not occur upon dissolving the trinuclear osmium carbonyl halides in acetonitrile and the cleavage of the Os-X bonds is a result of the electrochemical reduction. The observed order for ease of reduction of the trinuclear osmium carbonyl halides coincides with the change in the E1/2 values in the reduction of the mononuclear carbonyl halides of transition metals and alkyl halides.

1. As a result of chemical and electrochemical reduction the authors convert linear trinuclear osmium carbonyl halides to triangulo-dodecacarbonyl triosmium. 2. They study the polarographic reduction of linear compounds of osmium of the type X2Os3(CO)12 (X=Cl, Br, I). In contrast with C-X bonds in dihaloalkanes, dissociation of Os-X bonds involves a one-electron stage and leads to the formation of osmium carbonyl radicals which are subsequently converted into metal rings. 3. The ease of reduction of compounds of the type X2Os3(CO)12 depends on the electronegativity of the halogen atoms, and increases in the order X=Cl

1. The heterometallic complexes (Ph3P)(L)PtFe2(CO)8, like the homometallic compounds M3(CO)12 (M=Fe or Os), successively add two electrons under the conditions of electrochemical reduction in MeCN, being converted into radical anions and dianions, respectively. The reduction process is controlled by diffusion, and the value of the formation potential of the radical anion depends on the nature of L, decreasing along the series L=CO=PhsAs≅Ph3Sb≅Ph3P>(PhO)3P > (EtO)3P. 2. The electronic absorption spectra of the complexes (Ph3P)(L)PtFe2(CO)8 display bands which correspond to σ → σ* transitions between levels which are responsible for the formation of the metal-metal bonds, and it has been discovered that their position is influenced by the charge of the ligands attached to the Pt atom.

1. Reduction potentials in the polarographic reduction of multicentered rhenium and osmium carbonyl halides with cross-linking halogen atoms depend only slightly on the nature of the halogen atom. 2. The effect of n-donor compounds on complexes of the (μ-X)2Os3(CO)10 type is to cause substitution of the CO groups at the osmium atoms and to conserve Os2X2 metal ring.

The electrochemical reduction of η2-acetylenic derivatives of cymanthrene CpMn(CO)2-(PhC=CR) (R=H, Ph, SiPh3, and GePh3) proceeds in three consecutive steps. The addition of one electron in the first step leads to the elimination of the acetylenic ligand, which is reduced in the subsequent steps. The nature of R does not affect the course of the electrochemical reaction and is only slightly reflected in the reduction potential values.

By reacting the Na derivatives of metal carbonyls with l-chloro-3-trichlorostannyldodecacarbonyltriosmium ClOs3(CO)12SnCl3 we were the first to obtain pentanuclear linear compounds that contain a fragment composed of three osmium atoms in the metal chain.