Thallium organometallic compounds

It is now well established that organometallic compounds are formed in the environment from mercury, arsenic, selenium, tellurium and tin and hence were also deduced on the basis of analytical evidence for lead, germanium, antimony and thallium. Biological methylation of tin has been demonstrated by the use of experimental organisms. Methylgermanium and methyllead were widely found in the environment but it is debatable whether germanium and lead are directly methylated by biological activity in natural environment. 

A. McKillop, J. D. Smith, and 1. J. Worrall, Organometallic Compounds of Aluminium, Gallium, Indium and Thallium. Chapman Hall, London, 1985. 

In contrast to direct electrophilic substitution in which the astatine attacks one of the C—H bonds, astatination through demetalation can be used to label a substrate at a preferred site in a regiospecific manner not affecting other sensitive sites of the molecule. Since the C—M bond is more sensitive to electrophilic attack than C—H, higher yields can be obtained in short reaction times under milder experimental conditions56. Organometallic compounds of mercury, thallium and tin have been used so far for astatination via demetalation. 

Electrophilic demetalation of thallium trifiuoroacetate derivatives was utilized by Visser and Diemer60 to synthesize o-astatobenzoic acid and /7-astatoanisole. The organometallic compounds are formed by reaction of benzoic acid and of anisole with thallium trifiuoroacetate at room temperature, in the dark. Astatination was carried out in dilute H2S04, in the presence of KI within 30 minutes. Yields of70-90% were obtained the astati-nated products were separated by extraction and identified by TLC or—in the case of o-astatobenzoic acid—on the basis of its pKa value determined by extraction with heptane. 

Exposure to neurotoxicants or neurotoxic chemical substances causes severe adverse health effects to the nervous system, which is very sensitive to organometallic compounds and sulfide compounds. These compounds disrupt the normal functioning of the central nervous system, peripheral nerves or sensory organs, and the conduction of nerve impulses. Thus, chemical substances are considered neurotoxicants when they induce a consistent pattern of neural dysfunction. The chemical substances include but are not limited to carbon disulfide, manganese, methyl mercury, organic phosphorous insecticides, tetraethyl lead, thallium, and trialkyl tin compounds. 

The covalent trihalides of thallium(III) are less stable than the trihalides of the lighter metals of group 13. Aqueous solutions of these compounds are acidic because of their extensive hydrolysis. The compound TICI3 is an important starting material for the preparation of Tl organometallic compounds. 

Thallium diphenyl bromide was first mentioned by Meyer and Bertheim in 1994, but in 1922 the present authors showed that this compound was impure, and that the reactions given for it did not represent the facts, as shown by them later preparation. They therefore claimed their preparation to be the first organometallic compound of thallium, in the aromatic series, to be obtained in the pure state. The compound, which is typical of the aromatic thallium diaryl halides, does not melt below 300 C., and may be crystallised from pyridine. The corresjjond-ing chloride is decomposed "by iodine monochloride according to the equation ... 

In this review, primarily the developments in thallium coordination chemistry since the early 1980s will be surveyed. CCC (1987) is an excellent reference source for work prior to that time. In general, organometallic compounds are outside the scope of this article. There are several useful review and reference articles that describe thallium chemistry, including organothallium work. " " " Thallium is an important element in the field of high-temperature superconducting materials." ... 

Methyl, ethyl, propyl, and butyl halides are reduced at lead and tin cathodes to produce, respectively, the corresponding tetraalkyllead and tetraalkyltin compounds in excellent yield. Bismuth, gallium, indium, and thallium can be employed to prepare a variety of organometallic compounds. Feoktistov [2] and Hawley [4] have summarized many of these electrosyntheses. 

The Grignard reagent is the best-known member of a broad class of substances, called organometallic compounds, in which carbon is bonded to a metal lithium, potassium, sodium, zinc, mercury, lead, thallium—almost any metal known. Each kind of organometallic compound has. of course, its own set of properties, and its particular uses depend on these, fiut, whatever the metal, it is jess electronegative than carbon, and the carbon-metal bond—like the one in the... 

Information for other organometallic compounds is scarce. The corresponding methyl and ethyl derivatives of mercury, tin, and silicon were shown to undergo redistribution to yield random equilibrium mixtures of all possible metal alkyls. Rapid intermolecular exchange of the methyl groups in mixtures of trimethylaluminum-dimethylcadmium and dimethylzinc-dimethylcadmium was also demonstrated by NMR. The redistribution of mercury derivatives was found to be much slower. Further data are also available for thallium. - The four-center intermediate 154 was suggested to explain the observations [Eq. (6.149)] ... 

A. McKiUop and J. D. Smith, in Organometallic Compounds of Aluminum, Gallium, Indium, and Thallium , eds. 

In recent years, it has been proved that complex 120 is a unique species with a completely different chemical behaviour than that of previously reported compounds [44]. Its reactions with diolefins, oximes, and cyclopentadienyl thallium give rise to interesting organometallic compounds containing organic fragments, which are activated to afford carbon-carbon and carbon-heteroatom coupling reactions. 

Aluminum thallium and zinc porphyrins containing a metal carbon bond are synthesized by treating the porphyrins with organometallic compounds such as Al(Et)3 or Al(CH3)Cl2. 

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