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A. Patorra - One of the best experts on this subject based on the ideXlab platform.
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trifluormethyl substituierte Plumbane darstellung eigenschaften und nmr spektroskopische charakterisierung von cf3pbr2h r ch3 c2h5 sowie von cf3pb ii derivaten
Journal of Organometallic Chemistry, 1994Co-Authors: R. Eujen, A. PatorraAbstract:Abstract Unstable CF 3 PbMe 2 H has been isolated from the reaction of CF 3 PbMe 2 Br with Bu 3 SnH and has been identified by low temperature multinuclear NMR spectroscopy. Its decomposition yields the compounds CF 3 (CF 2 H)PbMe 2 and (CF 3 Me 2 Pb) 2 . Evidence for the intermittent formation of the much less stable Plumbanes (CF 3 ) 2 PbMeH and (CF 3 ) 3 PbH during the hydrogenation of the corresponding bromides was gained by their CF 2 insertion products (CF 3 ) 2 (CF 2 H)PbMe and (CF 3 ) 3 (CF 2 H)Pb, respectively, which give characteristic NMR spectra. Rapid deprotonation and dealkylation takes place even at −70°C if the bromides (CF 3 ) n PbMe 3− n Br ( n = 1–3) or CF 3 PbEt 2 Br are reacted with R 3 SnH (R = Me, n Bu) in a basic solvent such as DMF or pyridine, and trifluoromethylated lead(II) species are formed. In the presence of halide, the anion (CF 3 ) 3 Pb − , which has been obtained in high yield from (CF 3 ) 3 PbBr, releases a CF 3 group above −40°C. The NMR spectra of the product are in accord with the formulation of an equilibrium between (CF 3 ) 2 Pb and (CF 3 ) 2 PbBr − . Similarly, an equilibrium species “CF 3 Pb ⊕ · 2D” (D = DMF, Br − ) is derived from CF 3 PbR 2 Br which undergoes a CF 3 transfer reaction above −60°C to form “(CF 3 Pb · D (D = DMF, Br − ) and Pb 2⊕ .
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trifluormethylsubstituierte Plumbane synthese eigenschaften und nmr spektren der verbindungen cf3 npbr4 n n 1 3 und c
Journal of Organometallic Chemistry, 1992Co-Authors: R. Eujen, A. PatorraAbstract:Trifluoromethylated derivatives of lead, (CF3)nPbR4-n (n = 1–3; R = CH3, C2H5), have been prepared by a stepwise halide/CF3 exchange from (CF3)nPbR3-nX (n=O–2) and donor-stabilized (CF3)2Cd. Upon treatment of CF3PbR3 and (CF3)2PbR2 with halides under mild conditions, selective cleavage of the PbC(H) bond and formation of the corresponding alkyl(trifluoromethyl)haloPlumbanes were achieved, whereas with (CF3)3PbMe only (CF3)2PbMeX was obtained. The direct exchange of alkyl and trifluoromethyl groups was observed for the systems PbR4/(CF3)n E (E = Hg, Ge, Sn), (CF3)4Sn being the most efficient CF3 transfer reagent. All compounds were characterized by vibrational, mass and multinuctear NMR spectroscopy. The NMR coupling constants nJ(207PbE) (E = 19F, 1H, 13C), which vary strongly with solvents and substituents, have been determined along with their absolute signs. Linear correlations were found between 1J(207PbCF3) and 2J(207PbF) or 2J(207PbF) and 2J(119SnF) of homologous trifluoromethylated stannanes, respectively.
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Synthesis and spectroscopic properties of tetrakis(trifluoromethyl)Plumbane, (CF3)4Pb
Journal of Organometallic Chemistry, 1992Co-Authors: R. Eujen, A. PatorraAbstract:Abstract Tetrakis(trifluoromethyl)Plumbane, (CF 3 ) 4 Pb, has been prepared by aryl/CF 3 exchange from tetraarylPlumbanes, PbR 4 (R = phenyl, p -to
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Trifluoromethyl derivatives of lead — preparation and NMR spectra of (CF3)nPbR4−n (R = Me, Et; n = 1−3)
Journal of Fluorine Chemistry, 1991Co-Authors: R. Eujen, A. PatorraAbstract:Abstract Trifluoromethyl(alkyl)Plumbanes have been prepared by sequential trifluoromethylations utilizing (CF 3 ) 2 Cd.diglyme, followed by halogenations, and their reactivity has been studied. Instable CF 3 PbMe 2 H was obtained from CF 3 PbMe 2 Br and characterized along with its CF 2 insertion products. The Lewis acidity of the trifluoromethylated Plumbanes has been studied by NMR which show a large variation especially in the PbF and PbC coupling constants in the presence of various donors. The absolute signs of these couplings have been determined and a change of the sign of 1 J(Pbc) has been observed for electron-rich Plumbanes.
R. Eujen - One of the best experts on this subject based on the ideXlab platform.
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trifluormethyl substituierte Plumbane darstellung eigenschaften und nmr spektroskopische charakterisierung von cf3pbr2h r ch3 c2h5 sowie von cf3pb ii derivaten
Journal of Organometallic Chemistry, 1994Co-Authors: R. Eujen, A. PatorraAbstract:Abstract Unstable CF 3 PbMe 2 H has been isolated from the reaction of CF 3 PbMe 2 Br with Bu 3 SnH and has been identified by low temperature multinuclear NMR spectroscopy. Its decomposition yields the compounds CF 3 (CF 2 H)PbMe 2 and (CF 3 Me 2 Pb) 2 . Evidence for the intermittent formation of the much less stable Plumbanes (CF 3 ) 2 PbMeH and (CF 3 ) 3 PbH during the hydrogenation of the corresponding bromides was gained by their CF 2 insertion products (CF 3 ) 2 (CF 2 H)PbMe and (CF 3 ) 3 (CF 2 H)Pb, respectively, which give characteristic NMR spectra. Rapid deprotonation and dealkylation takes place even at −70°C if the bromides (CF 3 ) n PbMe 3− n Br ( n = 1–3) or CF 3 PbEt 2 Br are reacted with R 3 SnH (R = Me, n Bu) in a basic solvent such as DMF or pyridine, and trifluoromethylated lead(II) species are formed. In the presence of halide, the anion (CF 3 ) 3 Pb − , which has been obtained in high yield from (CF 3 ) 3 PbBr, releases a CF 3 group above −40°C. The NMR spectra of the product are in accord with the formulation of an equilibrium between (CF 3 ) 2 Pb and (CF 3 ) 2 PbBr − . Similarly, an equilibrium species “CF 3 Pb ⊕ · 2D” (D = DMF, Br − ) is derived from CF 3 PbR 2 Br which undergoes a CF 3 transfer reaction above −60°C to form “(CF 3 Pb · D (D = DMF, Br − ) and Pb 2⊕ .
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trifluormethylsubstituierte Plumbane synthese eigenschaften und nmr spektren der verbindungen cf3 npbr4 n n 1 3 und c
Journal of Organometallic Chemistry, 1992Co-Authors: R. Eujen, A. PatorraAbstract:Trifluoromethylated derivatives of lead, (CF3)nPbR4-n (n = 1–3; R = CH3, C2H5), have been prepared by a stepwise halide/CF3 exchange from (CF3)nPbR3-nX (n=O–2) and donor-stabilized (CF3)2Cd. Upon treatment of CF3PbR3 and (CF3)2PbR2 with halides under mild conditions, selective cleavage of the PbC(H) bond and formation of the corresponding alkyl(trifluoromethyl)haloPlumbanes were achieved, whereas with (CF3)3PbMe only (CF3)2PbMeX was obtained. The direct exchange of alkyl and trifluoromethyl groups was observed for the systems PbR4/(CF3)n E (E = Hg, Ge, Sn), (CF3)4Sn being the most efficient CF3 transfer reagent. All compounds were characterized by vibrational, mass and multinuctear NMR spectroscopy. The NMR coupling constants nJ(207PbE) (E = 19F, 1H, 13C), which vary strongly with solvents and substituents, have been determined along with their absolute signs. Linear correlations were found between 1J(207PbCF3) and 2J(207PbF) or 2J(207PbF) and 2J(119SnF) of homologous trifluoromethylated stannanes, respectively.
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Synthesis and spectroscopic properties of tetrakis(trifluoromethyl)Plumbane, (CF3)4Pb
Journal of Organometallic Chemistry, 1992Co-Authors: R. Eujen, A. PatorraAbstract:Abstract Tetrakis(trifluoromethyl)Plumbane, (CF 3 ) 4 Pb, has been prepared by aryl/CF 3 exchange from tetraarylPlumbanes, PbR 4 (R = phenyl, p -to
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Trifluoromethyl derivatives of lead — preparation and NMR spectra of (CF3)nPbR4−n (R = Me, Et; n = 1−3)
Journal of Fluorine Chemistry, 1991Co-Authors: R. Eujen, A. PatorraAbstract:Abstract Trifluoromethyl(alkyl)Plumbanes have been prepared by sequential trifluoromethylations utilizing (CF 3 ) 2 Cd.diglyme, followed by halogenations, and their reactivity has been studied. Instable CF 3 PbMe 2 H was obtained from CF 3 PbMe 2 Br and characterized along with its CF 2 insertion products. The Lewis acidity of the trifluoromethylated Plumbanes has been studied by NMR which show a large variation especially in the PbF and PbC coupling constants in the presence of various donors. The absolute signs of these couplings have been determined and a change of the sign of 1 J(Pbc) has been observed for electron-rich Plumbanes.
Sydney Leach - One of the best experts on this subject based on the ideXlab platform.
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Size Effects on Cation Heats of Formation. III. Methyl and Ethyl Substitutions in Group IV XH4, X = C, Si, Ge, Sn, Pb
The journal of physical chemistry. A, 2014Co-Authors: Sydney LeachAbstract:The heats of formation of alkyl-substituted XH4 (X = C, Si, Ge, Sn, Pb) molecular ions have often never been measured or are not known to better than 10 or 20 kJ/mol. The present study on these Main Group IV compounds adopts a graphical approach that relates cation heats of formation to cation size. A study of methyl substitution in XH4 is followed by a similar examination of heat of formation data on ethyl substitution in methane, silane, germane, stannane, and Plumbane. The results provide tests of the validity of this graphical method as well as its use as a predictive tool for determining cation and neutral heats of formation. Suggestions are made of the need to investigate or reinvestigate the ionization energies and/or the heats of formation of several of the molecules studied. Results and conclusions are tabulated.
Jan Kratzer - One of the best experts on this subject based on the ideXlab platform.
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Hydride generation – in-atomizer collection of Pb in quartz tube atomizers for atomic absorption spectrometry – a 212Pb radiotracer study
Journal of Analytical Atomic Spectrometry, 2013Co-Authors: Jan Kratzer, Stanislav Musil, Miloslav Vobecký, Jiří DědinaAbstract:Lead preconcentration on the quartz surface after Plumbane generation was extensively studied in the separate quartz trap or in the compact trap-and-atomizer device by means of a laboratory prepared 212Pb radioactive indicator. Plumbane generation efficiency of 95% was found. A large surface area is required for sufficient analyte trapping as found by autoradiography. The lead trapping efficiency in the separate trap is around 85% at 300 °C whereas 100% trapping is reached in the trap-and-atomizer device at the same temperature due to its greater inner surface. Volatilization of the trapped lead species at 800 °C is efficient for both the separate quartz trap and the trap-and-atomizer device. The non-volatilized lead fraction was below 5% in the trap-and-atomizer device at 800 °C. The non-volatilized lead fraction increases substantially in the presence of Bi. This was proved to be the mechanism of the serious Bi interference. Although 1–10 ng of analyte is typically preconcentrated in ultratrace analysis the quartz trap is capable of efficient trapping and subsequent volatilization of up to 200 ng Pb.
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Hydride generation - in-atomizer collection of Pb in a quartz trap-and-atomizer device for atomic absorption spectrometry - an interference study
Spectrochimica Acta Part B: Atomic Spectroscopy, 2012Co-Authors: Pavel Novotný, Jan KratzerAbstract:Abstract Interferences of selected hydride forming elements (As, Sb, Bi, Se and Sn) on lead determination by hydride generation atomic absorption spectrometry were extensively studied in both on-line atomization and preconcentration (collection) modes. The commonly used on-line atomization mode was found free of significant interferences, whereas strong interference from Bi was observed when employing the preconcentration mode with Plumbane collection in a quartz trap-and-atomizer device. Interference of Bi seems to take place in the preconcentration step. Interference of Bi in the collection mode cannot be reduced by increased hydrogen radical amount in the trap and/or the atomizer.
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Ultratrace determination of lead by hydride generation in-atomizer trapping atomic absorption spectrometry: Optimization of Plumbane generation and analyte preconcentration in a quartz trap-and-atomizer device
Spectrochimica Acta Part B: Atomic Spectroscopy, 2012Co-Authors: Jan KratzerAbstract:Abstract A compact trap-and-atomizer device and a preconcentration procedure based on hydride trapping in excess of oxygen over hydrogen in the collection step, both constructed and developed previously in our laboratory, were employed to optimize Plumbane trapping in this device and to develop a routine method for ultratrace lead determination subsequently. The inherent advantage of this preconcentration approach is that 100% preconcentration efficiency for lead is reached in this device which has never been reported before using quartz or metal traps. Plumbane is completely retained in the trap-and-atomizer device at 290 °C in oxygen-rich atmosphere and trapped species are subsequently volatilized at 830 °C in hydrogen-rich atmosphere. Effect of relevant experimental parameters on Plumbane trapping and lead volatilization are discussed, and possible trapping mechanisms are hypothesized. Plumbane trapping in the trap-and-atomizer device can be routinely used for lead determination at ultratrace levels reaching a detection limit of 0.21 ng ml − 1 Pb (30 s preconcentration, sample volume 2 ml). Further improvement of the detection limit is feasible by reducing the blank signal and increasing the trapping time.
Ian D Brindle - One of the best experts on this subject based on the ideXlab platform.
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determination of lead in calcium carbonate by flow injection hydride generation with dc plasma atomic emission detection
Spectrochimica Acta Part B: Atomic Spectroscopy, 1998Co-Authors: Ian D Brindle, Roger L Mclaughlin, Napa TangtreamjitmunAbstract:Abstract Flow-injection hydride generation, coupled with dc plasma atomic emission spectrometry has been used for the determination of trace lead concentrations in calcium carbonate matrices. The use of ferricyanide combined with sodium tetrahydroborate(III) enable the production of Plumbane from acid solution. The Plumbane is separated in a new gas–liquid separator and delivered to the plasma for determination. Detection limits for the technique are 0.7 ng ml−1. Precision of measurements at the 20 ng ml−1 level was 1.6% RSD. In an investigation of interferences, it was found that Fe(II), Fe(III), Cd(II), Co(II), Mn(II), Ni(II) and Zn(II) do not interfere. The presence of copper(II) at 1 μg ml−1 reduced the signal from lead by 50%. Samples can be analyzed at a rate greater than 60 h−1.
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Simultaneous reduction of arsenic and lead to hydrides by sodium tetrahydroborate(III) for inductively coupled plasma-atomic emission spectrometry: An investigation into the reaction medium.
Talanta, 1995Co-Authors: Hengwu Chen, Ian D BrindleAbstract:Nitroso R salt and potassium ferricyanide, in hydrochloric acid, have been used as the reaction medium for simultaneous generation of arsine and Plumbane, combined with inductively coupled plasma-atomic emission spectrometric detection. Both of the reagents enhance the lead signal and neither reagent inhibits the arsenic signal, provided that the potassium ferricyanide is mixed on-line with the analyte solution. Potassium iodide, which is used to prereduce As(V) to As(III), does not interfere with Plumbane generation in both reaction systems. Various parameters affecting the signals have been studied, and the hydrochloric acid-potassium ferricyanide system has proved to be a better reaction medium. Detection limits of lead and arsenic are 1.1 and 2.8 ng/ml, respectively, have been obtained in the HClK(3) Fe(CN)(6) system at a sample uptake rate of 1.5 ml/min.
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The influence of chelating reagents on Plumbane generation: Determination of lead in the presence of PAN-S.
Talanta, 1993Co-Authors: Hengwu Chen, Fulong Tang, Ian D BrindleAbstract:A series of 22 chelating reagents were tested for Plumbane generation. Besides nitroso R salt, the reagents Bromo Pyrogallol Red, Pyrocatechol Violet, Alizarine Red-S, 5-Br-PADAP and PAN-S could significantly enhance the lead signal. The PAN-S system has been optimized. The characteristic concentration (5 ml sample) is 1.3 ng/ml, and the RSD at the 50 ng/ml level is 3.9%. Lead spiked into tap water and natural water was determined by HG-AAS in the presence of PAN-S. Recoveries of spiked lead were between 90 and 105 %. Study of the mechanism suggests that the lead hydride might be directly generated from the chelated Pb(II) instead of the metastable Pb(IV).