- The Mechanism of the Reaction of (Arylthio)trimethylgermanes with Benzyl Bromides Giving Aryl Benzyl Sulfides. A Kinetic Study
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A kinetic study has been conducted on the reaction of (arylthio)trimethylgermanes with benzyl bromides.The reaction was found to be second order and the rate was largely accelerated in polar solvents.Both ρ values due to substituents on arylthio and benzyl groups revealed nucleophilic attack of the sulfur atom on benzylic carbon atom as the reaction mechanism.Rates of the reactions of trimethyl(p-tolylthio)stannane with substituted benzyl chlorides were also examined to compare the substituent effects.Steric crowd around the sulfur atom has been found as an important factor to control the reaction mechanism.
- Kozuka, Seizi,Tamura, Shoji,Ishibashi, Satoshi,Ohya, Sadamu,Tagaki, Waichiro
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- Mechanism of the Reaction of (Arylthio)trimethylgermanes with 1-Aryl-1-bromoethanes--Kinetic and Stereochemical Studies--
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Kinetic and stereochemical studies have been conducted on the reaction of (arylthio)trimethylgermanes with 1-aryl-1-bromoethanes.The reaction has been found to obey a first-order kinetic equation.The rates of the reaction of the substituted arylethanes were well-correlated with ?+ constants.Optically active 1-bromo-1-phenylethane gave racemic phenyl 1-phenylethyl sulfide by the reaction with trimethyl(phenylthio)germane.An SNL ionization of 1-aryl-1-bromoethanes has been suggested as the reaction mechanism.
- Kozuka, Seizi,Nitta, Takemi,Tamura, Shoji,Tagaki, Waichiro
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- Thermal decomposition of platinum(IV)-silicon, -germanium, and -tin complexes
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The thermal decomposition of a number of complexes of the type [PtMe2(Me3E)X(diimine)] (E = Si, Ge, Sn; X = Cl, Br, I) has been studied. The thermal stability of complexes, as determined by thermogravimetric analysis (TGA), varies depending on the diimine ligand in the order 2,2′-bipyridyl (bpy) > 4,4′-di-tert-butyl-2,2′-bipyridyl (bpy-tbu2) > N-(2-(dimethylamino)ethyl)pyridine-2-aldimine (paen-me2) > (2-imino-n-propyl)pyridine (py-n-pr). Stability also varies according to the trends E = Sn ≈ Ge > Si and X = I > Br > Cl. The products of thermal decomposition have also been determined by 1H NMR and three distinct modes of decomposition are evident: reductive elimination of Me3EX, reductive elimination of Me4E, and α-elimination of Me2E. The competition between reductive elimination of Me3EX and Me4E depends primarily on the halide, X, with the ratio Me3EX:Me4E highest for X = Cl and lowest for X = I. The competition between reductive elimination and α-elimination depends primarily on E, with the tendency to α-elimination of Me2E increasing as E = Si 2(Me3Si)(bpy)] as 233 ± 14 kJ mol-1.
- Levy, Christopher J.,Puddephatt, Richard J.
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p. 4115 - 4120
(2008/10/08)
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- Formation of Halide Complexes of Methyl- and Inorganic Germanium(IV) in Aqueous Hydrohalogenic Acid Solutions
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The reaction of methyl- and inorganic germanium(IV) hydroxides ((CH3)nGe(OH)4-n; n = 1, 2, or 3) with halide ions (X = Cl-, Br-, or I-) to form halide complexes ((CH3)nGeX4-n) in aqueous acidic solution has been investigated by liquid-liquid extraction, solid-liquid distribution (ion exchange), and 1H NMR spectrometry.It has been found that methylgermanium moieties are hard Lewis acids similarly to inorganic germanium(IV), because the stability constant of the halide complexes decreases in the order Cl- > Br- > I-.The stability constant for an X- ion increases as the number of methyl groups attached to the germanium atom increases.The species of inorganic-, monomethyl-, and dimethylgermanium are nonionic and have a tetrahedral structure in HX solution, and OJ- ions attached to the germanium atom are stepwise substituted by X- ions with an increase in HX activity.Trimethylgermanium alone forms a cation, when the activity of HX is not sufficiently high.These facts suggest that the transfer of a negative charge from methyl groups to the central germanium atom lowers the stability of the bond between the germanium atom (hard acid) and an OH- ion (hard base).
- Sohrin, Yoshiki
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p. 3363 - 3371
(2007/10/02)
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