[73491-34-6] · Cl2HgO8 · Mercury(II) Perchlorate · (MW 453.55)
Alternate Name: mercuric perchlorate.
Physical Data: d ca. 4 g cm-3.
Solubility: sol CH2Cl2, THF, DME; slightly sol alcohols; insol benzene, hexane, etc.
Form Supplied in: colorless lumps; widely available as the trihydrate.
Preparative Methods: can be prepared in situ by heating Mercury(II) Oxide and 60% aq HClO4 at 40-60 °C for 1-5 min, or at rt by mixing Mercury(II) Acetate and HClO4 in DME or THF.
Handling, Storage, and Precautions: acute poison; oxidizer; exposure to all mercury compounds is to be strictly avoided. Releases toxic Hg and Cl2 fumes when heated to decomposition. Protect from light.
Like other HgII salts, the perchlorate facilitates electrophilic additions across alkenic double bonds.1,2 Whereas oxymercuration normally occurs with anti stereoselectivity, products of syn addition have been observed for norbornene.3
Mercury(II) perchlorate and other HgII salts (namely sulfate, nitrate, and tetrafluoroborate) promote hydrolysis of vinyl halogenides to ketones (50-90%). The reaction is not catalytic and is believed to involve oxymercuration/dehalogenation (eq 1; X = Cl, Br).4 Other HgII salts, such as HgSO4, Hg(NO3)2, and Hg(BF4)2, react similarly.4
Monothioacetals of a-diketones can be converted into a-diketones upon oxidation with Hg(ClO4)2 (eq 2).5 Analogous reaction with Thallium(III) Nitrate in MeOH results in the formation of the corresponding dimethyl monoacetal.6
In the presence of Hg(ClO4)2, ethers (R1OR2) are formed from alkyl bromides (R1Br) and aliphatic alcohols (R2OH) via a nucleophilic substitution (R1, R2 = Me, Et, PhCH2).7
In addition to other HgII salts, Hg(ClO4)2 is also very effective in the cleavage of cyclopropanes (eq 3).8,9
University of Leicester, UK