Gold-thallium compounds

The number of compounds with Au-Tl interactions for which the structure has been investigated by single-crystal X-ray diffraction has increased considerably in the last years and some important molecular dimensions are collected in Table 4.3. 

The first Au-Tl compound, [AuTl CH2P(S)Ph2 2]n 23, was obtained by Fackler and coworkers by reacting [PPN][Au CH2P(S)Ph2 2] with n2S04 [35, 37]. In the molecular unit the Au(I) atom is linearly coordinated by two carbon atoms, while the sulfur atoms are coordinated to the T1(I) center. In the solid state an extended one-dimensional chain polymer is formed along the crystallographic b axis of the 

Long X-Tl (X = halogen) contacts between the thallium center and halogen atoms of the almost linear [AuR2] unit seem also to contribute to the stability of many of these systems. It is worth noting that theoretical studies revealed for the Au-Tl interaction in these systems a surprising calculated strength of about 276 kj mol-1, from which 80% is due to an ionic contribution and 20% to dispersion (van der Waals) [55]. 

Exposure of the solid [Tl Au(C6Cl5)2 ] 31 to vapors ofTHF provided crystals of [T1 (TH F)o.5 Au(C6Cl5)2 ]n 40 for which an X-ray diffraction study revealed that part of the 

The related pentachlorophenyl derivative, [Tl(4,4 -bipy) Au(C6Cl5)2 ] 70, was obtained as an orange solid, either by reacting the polymeric precursor 31 with an equimolecular amount of 4,4 -bipyridine or from complex 67 and half an equivalent of the aromatic amine [68]. Its solid-state structure is completely different from that of 

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Table 4.3 Selected molecular parameters for gold—thallium compounds. 

The complexes exhibited different behavior in solution. The gold-thallium derivative showed a shift of the emission to 536 nm when the measurement was carried out in frozen solution. This was explained by a higher aggregation of [Aull(MTP)2] units in the solid state compared to the situation in solution. In the case of the Au-Pb compound, the emission spectrum showed a strong dependence on the aggregation state and temperature. Thus, the emission band in TH F solution, which appeared at 555 nm (298 K) (x = 57 ns), was shifted to 480 nm in frozen solution (x = 2.3 ps) or appeared at 752 nm in solid state (x = 22 ns). As with the thallium complex, the shift to high energy in solution may have been related to the polymeric structure of the complex in the solid state that was not reproduced in solution. 

Uson, R., Laguna, A. and Cuenca, T. (1980) Chlorobis (polyfluorophenyl) thallium(III) complexes and their reactions with gold(l) and tin(ll) compounds. Journal of OrganometaUic Chemistry, 194(3), 271-275. 

The related reaction shown in Equation (104)117 leads to a butterfly arrangement with two thallium ions bridging between two gold atoms, 127. Here, the Tl-Tl distance is 360.27 pm and is thought to contribute significantly to the physical properties of the complex. The compound shows solvent-dependent luminescent behavior in solution as well as in the solid state. 

Uses. The unalloyed metal cannot be directly used owing to its bad mechanical properties and its high oxidability. Several thallium alloys are used as semiconductors or ceramic compounds it may be used as additive to gold, silver or copper contacts in the electronic industries. Thallium is dangerously toxic. 

The lack of homopolyatomic anions for elements to the left of group IV In Table I is noteworthy. Zlntl reported no success with reactions of alkali metal alloys of the copper and zinc family elements and of thallium with liquid ammonia, and the generally stabilizing effect of crypt has not been evident In our own Investigations of alloys of mercury and thallium. On the other hand. It is possible to Isolate a white crypt-potassium gold compound from ammonia solutions at low temperatures which decomposes to elemental gold (+ ) above about -10°C (30). 

Syntheses of near-single phases of the lead-substituted thallium monolayer phases with up to 6 Cu-O layers i.e., Pb-doped 1212, 1223, 1234, 1245, and 1256, have been recently reported (21). Reactant mixtures of various proportions of Tl2Os, PbO, CaO, Ba02, and CuO were pelletized, wrapped in gold foil, and sintered at 860-900°C under flowing oxygen for 10-30 h. The Tc value reached a maximum of 121 K for the 1234 compound and declined with further increase in the number of Cu-O layers. X-ray powder diffraction data for the different phases were refined using the Rietveld method and a consistent increase in the c-axis accompanied the increase in number of Cu-O layers. 

Thallium(III) compounds usually react to cause oxidation of gold(I), but in certain cases arylgold(I) species have been isolated [Eqs. (11) and (12)] (38, 39). Oxidative addition was prevented in the former due to the inability of X to form the necessary bridges in the intermediate species (J[Pg.45]

The yields of these reactions are often improved by the addition of thallium(I) or silver(I) salts to act as halide scavengers and so generate the gold phosphine fragment in situ. This modification has been most extensively utilized in the addition of Au(PR3)+ to anionic and neutral cluster compounds, and a number of examples are given below ... 

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