Ionic gold compounds

An interesting intermetallic gold compound is CsAu, where Au is bound to the most electropositive metal Cs (Xcs = 1-2). As a result we obtain an ionic bonding situation for the semiconductor Cs Au and not a metallic bond as one expects (two metals do not necessarily form a metallic bond ). Figure 4.12 nicely shows that the HOMO consists mainly of Au(6s) with much smaller Cs(6s) and Au(dn) participation, while the LUMO is mainly Cs(6s). Saue and co-workers calculated relativistic... 

Schreiter ER, Stevens JE, Ortwerth MF (1999) Gold compounds as ionic liquids synthesis, structures, and thermal properties of n, n-diaUsylimidazolium tetrachloroaurate salts. Inorg Chem 38 3935-3940... 

Hasan, M., Kozhevnikov, I.V, Siddiqui, M.R.H., Steiner, A. and Vtinterton, N., Gold compounds as ionic liquids. Synthesis, structures, and thermal properties of N,N-dialkylimidazoliumtetrachloroaurate salts, Inorg. Chem. 38 (25), 5637-5641 (1999). 

The preference of gold(III) for planar 4-coordination is such that ligands sometimes adopt unusual denticities. Therefore, Au(N03)J has four mono-dentate nitrates Au(terpy)Cl3.H20 contains Au(terpy)Cl2+ Aupy2Cl3 is Aupy2Cl2 CP Au(S2CNBu2)2Br is Au(S2CNBu2)2 Br- Au(S2CNBu2)3 has one bidentate and two monodentate dithiocarbamates and Au(NH3)4(N03)3 has only ionic nitrates, to quote compounds already mentioned. 

The compound CsAu is ionic, Cs Au RbAu was also thought to be ionic owing to xs Rb in the lattice but is now thought of as being a semiconductor. The preparation of CsAu is from a gold film with Cs vapor. The gold film is first... 

Unusual aurophilic bonding between gold in different oxidation states appears to be responsible for the adduct formation between (G6F5)3Au and cyclic ylide complexes with gold in the oxidation state +1 and +2 and in related compounds with an ionic structure (Scheme 24)155-157... 

The dehydration of thiobenzoylthioglycolic acid (135, R = Ph, R = H) with acetic anhydride-boron trifluoride was initially described as yielding the meso-ionic l,3-dithiol-4-one (134, R = Ph, R = H), but subsequent studies showed that the product was in fact the 5-substituted derivative 134, R = Ph, R = COCHjSCSPh. Authentic meso-ionic l,3-dithiol-4-ones (134) have recently been prepared (85-90% yield) by the cyclodehydration of the acids (135) with acetic anhydride-triethylamine at 0°-10°. Examples include anhydro-4-hydroxy-2-phenyl-l,3-dithiolium hydroxide (134, R = Ph, R = H) described as scarlet needles, m.p. 113°—115° this compound is sensitive to moisture. Anhydro-4-hydroxy-2,5-diphenyl-1,3-dithiolium hydroxide (134, R = R = Ph) was obtained as gold lustered, deep violet needles,... 

K, is shown in Fig. 7 by the filled circle [125]. Gold molecular compounds which have such negative I.S. values are strongly ionic and often quite unstable as well. 

Nonpolar molecular compounds dissolve in nonpolar solvents. Polar molecular compounds and ionic compounds may dissolve in polar solvents. Metals dissolve in other molten metals. These can range from copper, silver, gold, alkali metals dissolving in mercury at room temperature, to chromium, molybdenum, and tungsten dissolving in molten iron. 

The chemistry of compounds with gold-germanium bonds has developed considerably since Schmidbaur and coworkers reported the first derivatives obtained by the insertion reaction of GeCl2 (as its dioxane complex) into a gold-halogen bond [75]. Both neutral and ionic compounds have been reported and a larger structural diversity in comparison with the silicon analogs has been established (Table 4.4). 

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