Cations thallium

Thallium phthalocyanine (PcT12) can be obtained by heating phthalonitrile with an inter-metallic alloy of indium and thallium in an evacuated glass ampule.145 The structure of this compound is unique among metal phthalocyanines as the two thallium cations occupy two opposite corners of an octahedron, which is formed by the thallium cations and the four iso-indolinc nitrogen atoms facing the center of the macrocycle.147 Another unusual type of phthalocyanine can be prepared by heating phthalonitrile with thallium metal.148 It was identified as a bicyclic thallium(III) phthalocyanine (Pc3/2T1).14S... 

Concerning the structure of the pentachlorocyclopentadienyl-substituted thallium(I) compound LHIm it has been suggested that in the solid state the thallium cation nestles in the C5CI5 anion and that some charge is transferred from the anion to the empty thallium orbital (177), a situation typical for an ion pair with a low degree of covalent interaction. 

Metal oxygen cluster compounds with keggin structure have received attention as acid catalysts for several acid catalysed reactions in the liquid as well as in vapour phase conditions [1-6]. Studies on a series of salts with monovalent cations and various heteropolyanions have revealed that certain of these solids in particular those containing potassium, cesium,ammonium and thallium cations possess microporous structure [7-11]. Photoacoustic FTIR investigations and the studies on the chemisorption of ammonia and pyridine have shown that residual protons remain and these protons are responsible for the catalytic activity[12,13]. 

The complex UPsoPhs] represents a particularity as the thallium cation is T -bound in this species. A five-membered ring entirely surrounded by phenyl groups serves as a coordinahng unit (Figure 2.43). 

Chalcogen< osphides can be regarded as salts formed by a metal cation (in this case, thallium cation) and a chalcogenophosphide anion. It may be assumed that this anion forms of closed chains of various lengths (the length depends on the nature of the chalcogen). 

The use of phenyl triflate (2) was favoured over phenyl iodide, which gave very poor enantioselection, and it was postulated that employing the triflate allows the reaction to proceed by the cationic as opposed to the neutral pathway (Scheme 11.5). The cationic pathway was proposed as early as 1990 and begins with the dissociation of X (X = triflate or a halide in the presence of a halide scavenger such as silver or thallium cations) from the cationic complex with the accompanying counterion X (X = halide or triflate) [9]. Complexation of the alkene... 

The oxidation of the hydrazinium ion by Tl + probably involves substitution of hydrazine for water in the hydrated thallium(iii) species. The kinetics of complex formation between thallium(iii) and 4-(2-pyridylazo)resorcinol in aqueous solutions have been studied. Two pathways have been identified, involving Tl and [T10H] + reacting with the protonated ligand. The similarity in rate to that of the corresponding reaction of thallium(iii) with Semi-xylenol Orange indicates that the rate is controlled by loss of water from the hydrated thallium cation. ... 

Among the hydrophobes, there a significant difference in the extent of the "protection" of pyrene labels in the copolymers. The micropolarity of the hydrophobic microdomains probed by the /3//1 ratio of pyrene fluorescence decreases in Ae order of adamantyl > dodecyl > cyclododecyl domains (57). Furthermore, the protection of pyrene fluorescence from quenching by thallium cations in the bulk aqueous phase is much more effective in cyclododecyl domains than in dodecyl domains (79). 

Stereoselective cis-dihydroxylation of the more hindered side of cycloalkenes is achieved with silver(I) or copper(II) acetates and iodine in wet acetic acid (Woodward gly-colization J.B. Siddall, 1966 L. Mangoni, 1973 R. Criegee, 1979) or with thallium(III) acetate via organothallium intermediates (E. Glotter, 1976). In these reactions the intermediate dioxolenium cation is supposed to be opened hydrolytically, not by Sn2 reaction. 

A mild and effective method for obtaining N- acyl- and N- alkyl-pyrroles and -indoles is to carry out these reactions under phase-transfer conditions (80JOC3172). For example, A-benzenesulfonylpyrrole is best prepared from pyrrole under phase-transfer conditions rather than by intermediate generation of the potassium salt (81TL4901). In this case the softer nature of the tetraalkylammonium cation facilitates reaction on nitrogen. The thallium salts of indoles prepared by reaction with thallium(I) ethoxide, a benzene-soluble liquid. 

The classical view of the lone pair is that, after mixing of the s and p orbitals on the heavy metal cation, the lone pair occupies an inert orbital in the ligand sphere [6]. This pair of electrons is considered chemically inert but stereochemi-cally active [7]. However, this implies that the lone pair would always and in any (chemical) environment be stereochemically active, which is not the case. For example, TIF [8] adopts a structure, which can be considered as a NaCl type of structure which is distorted by a stereochemically active lone pair on thallium. In contrast TlCl [9] and TlBr [10] adopt the undistorted CsCl type of structure at ambient temperature, and at lower temperatures the (again undistorted) NaCl type of structure. The structure of PbO [11] is clearly characterized by the stereochemically active lone pair. In all the other 1 1 compounds of lead with... 

An asymmetric surrounding of thallium(I) in a crown ether (or cryptand) is especially surprising as these polyethers generally provide a highly symmetric surrounding for the coordinated cation. In fact, alkali-metal cations Hke sodium. 

In [Tl 18-crown-6] [CIO4] (Fig. 2.1), the thallium(I) cation resides 75 pm above the plane defined by the oxygen atoms of the crown ether and 66 pm in [ri 18-crown-6] [TII4] [39] whereas, for example, in the analogous potassium compound [K 18-crown-6] [CIO4] [40] the cation is found right in the middle of the crown ether (Fig. 2.2). 

On treatment with T1C1, alkali metal boratabenzenes afford the corresponding T1 compounds (51). The lower reactivity of these can be essential for some syntheses. Some of the rare cationic borabenzene complexes 35-37 could be made using thallium boratabenzenes as reagents. Similarly, (C4Me4)Co(CO)2I yielded the mixed sandwich complexes 38 and 39 in excellent yields (71). 

In the crystal, most trinuclear carbeniate complexes are known to be stacked with close aurophilic interactions, and organic 7r-acids can be intercalated into these stacks.252 Similar intercalation takes place with the cations of simple silver and thallium(i) salts. The cations become attached to form polymetallic core units through metallophilic bonding. With the trinuclear silver pyrazolates, both metal and ligand exchange have been observed to give new stacks of trinuclear units.254... 

The participation of cations in redox reactions of metal hexacyanoferrates provides a unique opportunity for the development of chemical sensors for non-electroactive ions. The development of sensors for thallium (Tl+) [15], cesium (Cs+) [34], and potassium (K+) [35, 36] pioneered analytical applications of metal hexacyanoferrates (Table 13.1). Later, a number of cationic analytes were enlarged, including ammonium (NH4+) [37], rubidium (Rb+) [38], and even other mono- and divalent cations [39], In most cases the electrochemical techniques used were potentiometry and amperometry either under constant potential or in cyclic voltammetric regime. More recently, sensors for silver [29] and arsenite [40] on the basis of transition metal hexacyanoferrates were proposed. An apparent list of sensors for non-electroactive ions is presented in Table 13.1. 

Al, Ga, In and T1 differ sharply from boron. They have greater chemical reactivity at lower temperatures, well-defined cationic chemistry in aqueous solutions they do not form numerous volatile hydrides and cluster compounds as boron. Aluminium readily oxidizes in air, but bulk samples of the metal form a coherent protective oxide film preventing appreciable reaction aluminium dissolves in dilute mineral acids, but it is passivated by concentrated HN03. It reacts with aqueous NaOH, while gallium, indium and thallium dissolve in most acids. 

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