Thallium-mercury bonds

The nature of the carbon-metal bond varies widely, ranging from bonds that are essentially ionic to those that are primarily covalent. Whereas the structure of the organic portion of the organometaiiic compound has some effect on the nature of the carbon-metal bond, the identity of the metal itself is of far greater importance. Carbon—sodium and carbon-potassium bonds are largely ionic in character carbon—lead, carbon—tin, carbon—thallium, and carbon—mercury bonds are essentially covalent. Carbon—lithium and carbon—magnesium bonds lie between these extremes. 

The reactions of acetylenes with thallium(III) salts are of considerable interest in that the results can be used in a qualitative comparison of reactivity between thallium(III) and mercury(II). Mercury(II) salt-catalyzed hydration of the C=C bond is a much studied and synthetically very useful process, although the detailed mechanism of the reaction is not known. The only published data available on the reactions of acetylenes with thallium-(III) salts are due to Uemura et al. 161), who employed thallium(III)... 

Thallium(III) substituents (see 36) exert even larger effects on a-caibon atoms than mercury does (141) (see 37 and 38) this has been ascribed to displacement of electrons in the carbon-metal a-bond toward the metal atom, due to its increased nuclear charge. 

Among some metal oxygen compounds which add, palladium and thallium ion both oxidize olefins and apparently the initial step is the addition of a metal hydroxide across the olefin double bond. The intermediates have not been isolated because they go on to other products but kinetic and other evidence indicates that the addition of the hydroxide is the initial step. In the well known mercury acetate addition to olefins in alcohol solution one can isolate the /S-hydroxv or alkoxy ethylmercury derivatives. 

Sulfonation. Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of S03 or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Thphenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thallium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation. 

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. 

The term organometallic refer to compounds that contain a carbon-metal bond. [59] The term spans compounds that are primarily ionic (such as when the metal is sodium or potassium and thus should be nomenclated as the distinct ions) through compounds that are primarily covalent (such as when the metal is lead, tin, mercury or thallium for which the bonding is covalent)... 

Owing to the weakness of the Tl-C bonds, triorganothallium derivatives are highly reactive compounds. Trimethyl-and triphenylthallium react with mercury to form the corresponding diorganomercury derivatives and elemental thallium (equation 9). ... 

Lead, like its neighbor tin, enjoys both the -t-2 and +4 oxidation state. In this case, Pb(II) is the normal metallic cation and the Pb(IV) state is rather unstable and very often oxidizing. As such, any species that might contain a bonded Pb(IV) and an enolate anion may mimic Pb(II) and an enoxyl cation. Metal-metal exchange reactions of lead enolates show both enolate and enoxyl cation behavior , depending on what is affixed to the metal. This quasi-enolate vs. enoxyl cation dichotomy is also seen for suitable mercury-and thallium-containing species. 

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... 

In its covalent compounds thallium shows no reluctance to utilizing the two 6s electrons for bond formation. Indeed monoalkyl derivatives Tl(Alk) in which the valence group would be (2, 2) are not known, whereas trialkyls (valence group 6) are known and the most stable alkyl derivatives are the dialkyl halides such as [T1(CH3)2]I. These are ionic compounds-[T1(CH3)2] OH being a strong base—and in the Tl(Alk)2 ions the thallium atom has the same outer electronic structure as mercury in CH3-Hg-CH3, viz. (4). Accordingly the (CH3-T1-CH3) ion is linear, as shown by the determination of the crystal structure of Tl(CH3)2l. In molecules such as Tl(Alk)2A, where A represents a molecule of a /3-diketone, T1 apparently has the valence group (8). 

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