- Selectivity and reactivity in reactions of methylaryltitanium(IV) complexes with electrophiles
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Methyl or phenyl for halogen-exchange reactions occur between [TiMe2(η-C5H5)2] or [TiPh2(η-C5H5)2] with [TiX2(η-C5H5)2], X = halogen, to give [TiXMe(η-C5H5)2] or [TiXPh(η-C5H5)2], respectively. The reactions are complicated by parallel decomposition of the methyl- or phenyltitanium complexes, which is catalyzed by [TiX2(η-C5H5)2] or [TiXR(η-C5H5)2]. In general, there is little difference in the rates of reaction of [TiMe2(η-C5H5)2] and [TiPh2(η-C5H5)2] toward the symmetrization reactions. These reagents also transfer a methyl group or phenyl group to platinum(II) or gold(III), but there are again side reactions. The complex [TiMePh(η-C5H5)2] reacts with electrophiles HCl, HOAc, HgCl2, and MeHgCl to give cleavage of both methyl- and phenyltitanium bonds with little selectivity. In cleavage of [TiMe(C6H4X)(η-C5H5) 2] there is a correlation of the selectivity for cleavage of the aryl group by electrophiles HCl or HgCl2 with the σ+ parameters of substituents X. A mechanism of reaction involving electron transfer from the complex to the electrophile followed by rapid cleavage is tentatively suggested.
- Puddephatt, Richard J.,Stalteri, Maria A.
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p. 1400 - 1405
(2008/10/08)
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- MISE EN EVIDENCE EXPERIMENTALE DES HYDRURES RHgH
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The compounds RHgH have been characterised in methanol solution by their polarographic oxidation wave.Their decomposition and their action on RHgH products have also been studied.
- Devaud, Marguerite
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p. C27 - C29
(2007/10/02)
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- NMR INVESTIGATION OF ARYL- AND BENZYL-MERCURIC COMPOUNDS; EXPERIMENTAL EVIDENCE FOR ?-? CONJUGATION INVOLVING THE CARBON-MERCURY BOND
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199Hg and 13C NMR spectra of a large number of aryl- and benzyl-mercuric compounds (ArHgX and ArCH2HgX) have been obtained, in order to throw more light on the relationship between the coordination state of the mercury atom and its NMR parameters.For the aryl series ArHgCl there is a good correlation between the 199Hg chemical shift and ?+, with electron releasing substituents in Ar resulting in an upfield chemical shift.This correlation arises from the contribution of the paramagnetic term to the chemical shift.Comparison of the NMR parameters in ArHgCl and ArCH2HgCl provides unambiguous evidence for conjugation between the C-Hg bond in ArCH2HgCl and the aromatic ring, the C-Hg system behaving as a strongly donating group.This is explained in terms of vertical stabilization, as proposed by Traylor.
- Michel, Elie,Perie, Jacques,Lattes, Armand
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