Mercury crown compounds

Following the preparation of 4.79, a number of other cyclic mercury crown compounds have been synthesised, which do exhibit halide complexation behaviour. Compound 4.80, forms a 1 1 polymer with bromide in the solid state in which the Hr anions perch above the Hg3 plane. The Hg—Br distances of 3.07-3.39A are considerably longer than normal Hg—Br covalent bonds (about 2.54A).61 The compound also binds SCN- with similarly long bonds as shown in Figure 4.34.60 The analogous chloride complex has a 3 2 stoichiometry suggesting a triple-decker sandwich of type [4.80 Cl 4.80 Cl 4.80]2. ... 

Tikhonova, I. A., Dolgushin, F. M., Yanovsky, et al, Crown compounds for anions. A polymeric complex of cyclic trimeric perfluoro-o-phenylenemercury with thiocyanate anion containing an infinite helical chain of alternating molecules of mercury-containing macrocycle and SCN- ions. J. Organomet. Chem. 1996, 508, 271-273. 

Figure 3. Crystal structure of receptor 36 with bound bromide ions. [Reprinted from J. Organo-mel. Chem.. 418. C29. V. B. Shur, A. Tikhonova. A. I. Yanovsky, Y. T. Struchkov, P. V. Petrovskii, S. Y. Panov. G. G. Furin, and M. H. Vol pin. Crown compounds for anions. Unusual complex of tremeric perfluoro-o-phenylene mercury with the bromide anion having a polydecker sandwich structure C29, 1991, with kind permission of Elsevier Science SA, Lausanne, Switzerland.]...

Before the determination of mercury with dithizone, it can be separated with high selectivity from the acetate medium, in the presence of picric acid, by using a chloroform solution of l,3-diaza-2-thiabenzo-15-crown-5 [35] or related compounds [36]. 

Organomercury crown ether derivatives have been structurally characterized as threaded host-guest complexes of bis(trifluoromethyl)mercury with dibenzocrown ethers [394, 395]. Other threaded diorganomercury host-guest complexes of crown ethers have been studied in solution [396-398]. Internally complexed organomercury compounds (with Hg-Me and other groups) and l,3-xylyl-18-crown-5, e.g. 102, are also known [399]. 

In some cases template centres not commonly used to synthesise the corresponding compounds can be involved as matrices. In particular, in addition to alkali and alkaline earth metal ions, certain fluorine-containing silver, mercury, nickel, copper and zinc salts are suited to the synthesis of crown ethers, whereas an organometallic iron(II) compound serves as an effective template in the synthesis of 12-crown-4. 

Considering the denticity of ligand products typically assembled, the most often encountered are tetradentate macrocycles, followed by hexadentate species. Potentially tridentate macrocyclic products are described for nickel(II), copper(II), bor-on(III) and molybdenum(O) silver(I) and mercury(II) promote assembling penta-dentate and hexadentate macrocycles thallium(I), strontium(II), lanthanum(III) and the lanthanides(IIl) from Ce to Gd (Pm was not studied bccau.sc of its radioactivity) hexadentate products and the metal ions from Tb to Lu promote the formation of tetra- and hexa-dentate macrocyclic ligand products. Variable denticity of synthesised systems is conunon to most first-row transition elements as well as to alkaline metal ions which serve mainly to form crown ethers and related compounds. 

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