Anatoly I. Rubaylo

Chemistry of vinylidene complexes. XIII. The reaction between Cp(CO)2MnPt(μ-CCHPh)(η2-dppm) and Fe2(CO)9: simultaneous formation of the μ3-vinylidene MnFePt and μ4-vinylidene PtFe3 clusters. Crystal structure of (η5-C5H5)MnFePt(μ3-CCHPh)(CO)6[η1-Ph2PCH2P(O)Ph2] ☆ ☆☆

Abstract The reaction between [Cp(CO)2MnPt(μ-CCHPh)(η2-dppm)] 2 (1) and [Fe2(CO)9] gives heterometallic MnFePt and PtFe3 vinylidene clusters 2–4, in which diphosphine ligands are coordinated to metal cores in three different modes. In [(η2-dppm)PtFe3(μ4-CCHPh)(CO)9] (2) the Pt atom is chelated by dppm while in [CpMnFePt(μ3-CCHPh)(μ-dppm)(CO)5] (3) dppm bridges the Pt–Fe bond. Complex 3 was shown to exist in two isomeric forms. The novel complex {CpMnFePt(μ3-CCHPh)(CO)6[η1-Ph2PCH2P(O)Ph2]} (4), characterized by X-ray diffraction study, possesses a trimetallic chain core. The diphosphine ligand in 4 links to platinum by only one of phosphorus atoms whereas the second P atom is uncoordinated and oxidized to the phosphineoxide group.

Chemistry of vinylidene complexes XI. Synthesis of trinuclear MnFePt complexes by means of consecutive assembling out of mono- and dimetal vinylidene precursors

The dimetal μ-vinylidene complexes Cp(CO)2MnPt(μ-C = CHPh)L2 (L = tert.-phosphine or -phosphite), which have been obtained by coupling of the mononuclear complex Cp(CO)2Mn=C=CHPh and unsaturated PtL2 unit, add smoothly the Fe(CO)4 moiety to produce trimetal MnFePt compounds. The μ3-vinylidene cluster CpMnFePt(μ3-C=CHPh)(CO)6(PPh3) was prepared in quantitative yields from the reactions of Cp(CO)2MnPt(μ-C=CHPh)(PPh3)L (L = PPh3 or CO) with Fe2(CO)9 in benzene at 20 °C. The phosphite-substituted complexes Cp(CO)2Mnpt(μ-C=CHPh)L2 (L = P(OEt)3 or P(OPri)3) react under analogous conditions with Fe2(CO)9 to give mixtures (2:3) of the penta- and hexacarbonyl clusters, CpMnFePt(μ3-C = CHPh)(CO)5L2 and CpMnFePt(μ3-C = CHPh)(CO)6L, respectively. The similar reaction of the dimetal complex Cp(CO)2MnPt(μ-C = CHPh)(dppm), in which the Pt atom is chelated by dppm = Ph2PCH2PPhPin2 ligand, gives only a 15% yield of the analogous trimetal μ3-vinylidene hexacarbonyl product CpMnFePt(μ3-C = CHPh)(CO)(dppm), but the major product (40%) is the tetranuclear μ4-vinylidene cluster (dppm)PtFe3(μ4-C = CHPh)(CO)9. The IR and 1H, 13C and 31P NMR data for the new complexes are reported and discussed.

New peak broadening parameter for the characterization of separation capability in capillary electrophoresis

The influence of separation conditions on peak broadening is usually estimated by the number of theoretical plates. Using the data available in literature and experimental data, it is shown that in pressure-assisted capillary electrophoresis the plate number is not directly related to the separation capability of conditions used. The experiments at different electrolyte flow velocities demonstrate that a higher plate number (the best separation efficiency) can be obtained with a lower peak resolution. Since ions are separated by electrophoresis due to the difference in electrophoretic mobilities, the peak width in terms of electrophoretic mobility is suggested as a new peak broadening parameter describing the separation capability of the conditions used. The parameter can be calculated using the tailing factor and the temporal peak width at 5% of the peak height. A simple equation for the resolution calculation is derived using the parameter. The advantage of the peak width in terms of mobility over other parameters is shown. The new parameter is recommended to be used not only in pressure-assisted capillary electrophoresis but also in general capillary electrophoresis when in a number of runs the virtual separative migration distance and separation capability of the conditions used change widely.

System peaks and optimization of anion separation in capillary electrophoresis with non-reversed electroosmotic flow

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.

Chemistry of vinylidene complexes XII. Transmetalation of the μ-vinylidene ligand in the reaction of Cp(CO)2MnPt(μ-CCHPh)(dppp) with Fe2(CO)9. Formation of new PtFe, PtFe2 and PtFe3 complexes

Abstract The reaction between [Fe 2 (CO) 9 ] and [Cp(CO) 2 MnPt(μ-C CHPh)(dppp)] ( 1 ), where dppp is Ph 2 P(CH 2 ) 3 PPh 2 , proceeds stepwise, initially through transmetalation of the bridging vinylidene ligand, i.e. with replacement of the [Mn(CO) 2 Cp] 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 [Fe 2 (CO) 9 ] to yield the tetranuclear cluster [(dppp)PtFe 3 (μ 4 -C CHPh)(CO) 9 ] ( 3 ) and the trinuclear complex [(dppp)PtFe 2 (CO) 8 ] ( 4 ). The IR and 1 H, 13 C and 31 P NMR data for the new complexes are reported and discussed.

Determination of iron and copper ions in cognacs by capillary electrophoresis

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.

Determination of stability constants of inclusion complexes of betulin derivatives with β-cyclodextrin by capillary electrophoresis

67 Betulin and its derivatives relating to pentacyclic triterpenoids of lupan series exhibit pharmacological activity including human immunodeficiency virus inhibition, as well as antibacterial, antimalarial, anti inflammatory, antioxidant, and anticancer activity [1–3]. However, their medical application is rather limited because of their low solubility in water, which hampers the preparation of formulation for injection in humans.

Infrared study of transformation of a terminal carbonyl ligand into a bridging one in the MnPt and MnPd μ-vinylidene complexes

Abstract The IR study of a series of heterometallic vinylidene-bridged complexes CP(CO) 2 MnM( μ -C = CHPh)LL′, where M = Pt or Pd, L and L′ = CO, tert -phosphites, PPh 3 , Ph 2 P(CH 2 ) n PPh 2 , n = 1–3, demonstrated the existence of a gradual transformation of one of the terminal CO groups at the Mn atom into bridging one spanning the Mn-M bond, which goes through the intermediate semi-bridging form and is induced by the electron-donating capacities of ligands L and L′ at the M atom.

Strategy for non-target ionic analysis by capillary electrophoresis with ultraviolet detection

AbstractA 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 AbstractThe scheme of performing the non-target ionic analysis by capillary electrophoresis with ultraviolet detection

Influence of Analyte Concentration on Stability Constant Values Determined by Capillary Electrophoresis

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.