Carbon tetrachloride metal atoms

Rodionova and Ivanov [667] used chelate extraction in the determination of copper, bismuth, lead, cadmium, and zinc in seawater. The metal complexes of diethyl and dithiophosphates are extracted in carbon tetrachloride prior to determination by atomic absorption spectrometry. 

Discrete dimers of the head-to-head type have been found in the structures of the Ag+ complex of (145)570 and the Na+ complex of (145)571 respectively. The complexes were recrystallized from carbon tetrachloride. In both complexes each metal is five-coordinated in the cavity provided by one anion, and there is an additional reaction with the second anion [through an Ag+-phenyl interaction or an Na+-carboxylate oxygen atom (Figure 32a)]. When the Na+ complex was crystallized from a solvent of medium polarity, acetone, the head-to-head dimer was recovered.571 In contrast, recrystallization from a polar medium, methanol, gave a monomeric complex in which one methanol of solvation was also present.572 In all of these complexes an intramolecular head-to-tail hydrogen bond was present to hold the ligand in its pseudo-macrocyclic conformation. 

In the case of rhodium, however, it was demonstrated early that in the synthesis of [Rh6C(CO)l5]2 the encapsulated carbon atom originated as chloroform, which had reacted with the rhodium carbonyl anion [Rh7(CO)l6]3- (59). In the cobalt analog, [Co6C(CO)l5]2-, the carbon atom is derived indirectly from carbon tetrachloride [via Co3(CO)9CCl] (60) Both these syntheses are performed under mild conditions, and there are apparently no examples of carbidocarbonyl clusters of cobalt or rhodium prepared directly from the metal carbonyls under pyrolysis conditions. 

Susuki and Tsuji reported the first Kharasch addition/carbonylation sequences to synthesize halogenated acid chlorides from olefins, carbon tetrachloride, and carbon monoxide catalyzed by [CpFe(CO)2]2 [101]. Its activity is comparable to or better than that of the corresponding molybdenum complex (see Part 1, Sect. 7). Davis and coworkers determined later that the reaction does not involve homolysis of the dimer to a metal-centered radical, which reduces the organic halide, but that radical generation occurs from the dimeric catalyst after initial dissociation of a CO ligand and subsequent SET [102]. The reaction proceeds otherwise as a typical metal-catalyzed atom transfer process (cf. Part 1, Fig. 37, Part 2, Fig. 7). 

The alkali metals are easily vaporized at temperatures of 300—500"C, and most studies of this group have been reviewed in Sections 2 and 3. The reactivity of alkali metals in co-condensation reactions is high, but little different from that in diffusion flame studies. However, the alkali metals have been used in a number of low-temperature reactions, largely to produce radicals or intermediates of spectroscopic interest. For example, the trichloromethyl radical has been produced in a solid argon matrix by reaction of lithium atoms with carbon tetrachloride [294]. A similar technique has been used to produce the CBr2H radical from bromoform [295], the CCljH radical from chloroform [296], and the methyl radical from methyl iodide and methyl bromide [297]. In all these cases the corresponding lithium halide is produced. 

When acetylene tetrachloride is suspended in water and treated with zinc, two chlorine atoms are removed, the water becomes hot, and dichloroethylene, CHC1 = CHC1 (b.p. 55°) distils off. When the tetrachloride is boiled with milk of lime, or passed over barium chloride heated at 350°, hydrogen chloride is eliminated and trichloroethylene, CCl2 = CHCl (b.p 88°) is formed. The compound is an efficient solvent for fat, it does not attack metals, and does not produce hydrochloric acid slowly in contact with water. For these reasons it is preferred to carbon tetrachloride for many uses. 

Rigin (1990) extracted mercury and other metals from digested samples as di(trifluo-roethyl)dithiocarbamates into carbon tetrachloride, separated them by gas chromatography and determined them by AFS after atomization in an ICP. He reported a detection limit of 0.01 [Pg.426]

All Group IV elements form tetrachlorides, MX4, which are predominantly tetrahedral and covalent. Germanium, tin and lead also form dichlorides, these becoming increasingly ionic in character as the atomic weight of the Group IV element increases and the element becomes more metallic. Carbon and silicon form catenated halides which have properties similar to their tetrahalides. 

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