Mercury Dimercury compounds

Heating of the dimercury(I) compound Hg2As206 gives a mercury(II) compound of the same composition, crystallizing in the PbSb206 structure type with [As206]2 layers and Hg in a pseudo-octahedral environment (r(Hg—O) 235.3 pm).30... 

The reaction between dimercury(I) salts and molecules with an electron-pair-donating atom normally destroys the metal-metal bond of the dimercury(I) ion Hg+—Hg+ by disproportionation, forming metallic mercury and a mercury(II) compound, but the use of nonpolar solvents, weak Lewis bases and dialytic crystallization methods has contributed to the successful preparation of single crystals of several dimercury(I) coordination compounds in the past 25 years.9,30,31 The myth that the dimercury(I) species Hg + forms few coordination compounds has been exploded. 

Mercury compounds are more soluble in concentrated HNO3 than in water or the dilute acid. Nitric acid dissolves all common insoluble compounds of mercuiy except HgS, which, however, may be converted to the more soluble complex Hg3S2(N03)2, white, by boiling with concentrated acid. All dimercury(I) salts are oxidized to mercury(II) compounds by excess of HNO3. 

There are a number of books and articles on general aspects of the coordination compounds of mercury annual surveys are published in Coordination Chemistry Reviews5 and the Annual Reports on the Progress of Chemistry, Section A (Inorganic Chemistry—Mercury).6 McAuliffe s book The Chemistry of Mercury covers the literature up to May 1975.7 The coordination chemistry of mercury(II) halides has been summarized by Dean, covering papers up to 1977.8 A review of dimercury(I) coordination compounds was published by Brodersen in 1981,9 and in the same year Grdeni6 reviewed bonding in the crystal structures of mercury compounds.10... 

There is little evidence for the formation of soluble complexes in aqueous solutions of Hg1 halide and pseudohalide systems,12,32 but the mercury(I) halides themselves are well-known substances. X-ray studies on the dimercury(I) dihalides show that all these compounds possess... 

Diacetoxymercuri 0-chloroaniIine, NHg.CellaC Hg.OAc., decomposes at 220° C., and yields an hydroxide decomposing at 250° C. and a chloride at 190° C. The acetate gives an acetyl derivative, M. pt. 230° C., from which 2 4 6-trichloroaniline may be obtained in the usual way. The acetyl derivative of the cWoride decomposes at 276° C. The action of sodium thiosulphate on the acetate results in the production of a compound decomposing at 200° C., which is either 4 6-mercuri chloro-aniline (I.) or 4 6-dimercuri-bis-o-chloroaniline (II.)... 

Nitro-3-h5 droxybenzaldehyde also yields a mixture of compounds. The dimercurated product appears to be a hydroxymercuri-acetoxy-mercuri-4-nitro-3-hydroxybettzaldehyde. It is insoluble in most solvents, but gives 2 Q-diformomydimercuri- -nitro-Z-hydroccybenzahk-hyde from hot formic acid solution. It crystallises in pale yellow needles, which darken at 120° C. and explode at 257° C. When boiled with formic acid, metallic mercury separates. It gives a red solution in potassium hydroxide, from which hydrochloric acid precipitates the 2 Q-dichloro-dimercuri derivative This crystallises from alcohol in bundles of minute, pale yellow needles, which darken at 240° C. but do not melt at 300° C. When heated in vacuo it loses a molecule of water at 60° C., and decomposes at 282° C. (corr.). Its potassium hydroxide solution is decomposed by carbon dioxide with precipitation of 2 3-anhydro-2 6-dihydroxymercuri"4-nitro-3-hydroxybenzaldehyde. The dimercurated compound may be converted by the usual means into a di-iodo-4-nitro-3-hydroxybenzaldehyde,... 

Oxidation numbers for Hg (I) and (II), as in Hg20, mercurous oxide, HgO, mercuric oxide, and Hg 0 2 [mercuiy(ll) peroxide]. The mercurous ion is dimercury(2+) or dimercury(I), Hg2. Relativity greatly strengthens the Hg-Hg bond but may also explain the metal s liquidity. Relativity shrinks and stabilizes mercury s 6s orbital, making Hg rather like a noble gas but favoring linear sp hybrids with more (1/2 s) low-energy s nature than the tetrahedral sp (1/4 s). The many (linear) oigano-mercury compounds are excluded here. 

Bravo-Zhivotovskii D, Ruderfer I, Yuzefovich M, Kosa M, Botoshansky M, Tiunanskii B, Apeloig Y (2005) Mercury-substituted silyl radical intermediates in formation and fragmentation of geminal dimercury silyl compounds. Organometallics 24 2698... 

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