Organomercury halides

The sum of the van der Waals radii for the mercury-chlorine pair is ca. 3.90 A (the value of the van der Waals radius of mercury is still controversial but a value of 1.73 A has been suggested [71]) and distances shorter than this will be considered in discussing supramolecular self assembly. A good illustration of supramolecular dimer formation is that of the anions [(CF3)2Hg( -F)2Hg(CF3)2] , 12, (Hg-F 2.395 A, Hg- F 2.418 A, probably a dative bond) [72] and [(CF3)2Hg(/x-Cl)2- 

Two non-equivalent mercury-chlorine bonds indicating complete separation of covalent and secondary bonding, were found in dimeric (phenylazophenyl-C,A )mercury chloride, 14. In addition to the bond leading to dimerization, another secondary interaction with a chlorine of a different molecule occurs at 3.632 A 

The four-membered ring unit Hg2Cl2 can occur as a part of a ladder structure. Thus, (2-pyridylphenyl)mercury(II) chloride, 15a, is a tetramer, with the skeleton shown in 15b (only atoms directly bonded to mercury are shown for clarity). The mercury-chlorine interatomic distances are in the range 3.184-3.442 A [75]. 

34 A and secondary Hg- -Cl 3.20-3.38 A) [77]. Benzylmercury chloride, PhCH2HgCl, forms a ladder-type supramolecular array [78] and pentamethyl-cyclopentadienyl mercury(II)chloride, tr-CsMesHgCl, is a self-organized ribbon (Hg-Cl 2.350-2.361 A, Hg- -Cl 3.098-3.238 A) running as a zigzag ladder in the crystal [79]. 

Another ladder containing Hg-Cl primary bonds (2.329 and 2.345 A) and secondary Hg- - -Cl bonds (3.303-3.566 A) has been reported in meso-a,ix-bis-(chloromercurio)-a,a -bis(trimethylsilyl)-m-xylene [80], 17, and an intricate compact 

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Frequently, a substrate anion-radical quickly decomposes, giving off the organic radical, and only then transforms into the hnal product. In this case, usual inhibitors of radical reaction are employed and the reaction mechanism is disclosed from the nature of the products. Thus, the transfer of an electron from the anion-radical of naphthalene to organomercury halides gives naphthalene and substrate anion-radical. The latter decomposes in two stages—[RHgHal] Hal + RHg ... 

In certain instances (Ir, Pt, Au), the carbon-transition-metal-mercury complexes are actually isolable. They also decompose in the manner indicated. When organomercury halides are employed in such reactions, similar oxidation-reduction processes occur, but evidence suggests that the transition metal inserts primarily into the mercury-halogen bond followed by loss of mercury " ... 

Unsymmetrical diaryl ketones are obtained by the reaction of iodobcnzene with nickel carbonyl in the presence of an organomercury halide ... 

As well as the organomercury halides, carboxylates also undergo insertion with diazomethane, e.g. ... 

Phenols.5 Organomercury halides of the type ArHgX react with diborane in THF under normal hydroboration procedures to give intermediate organoboranes which are not isolated but oxidized with alkaline hydrogen peroxide to give phenols in good yield. 

Takemoto, Y., Ohra, T., Yonetoku, Y, Nishimine, K., and Iwata, C., Novel intramolecular Michael addition of organomercury halides mediated by a Lewis acid and halide anion, J. Chem. Soc., Chem. Commun., 81, 1994. 

Metal exchange is not limited to diorganomercurials but can also be performed with organomercury halides ... 

The activation entropy for thermal decomposition of /ra j -[MnX(CO)3(PPh3)2] indicates that manganese-phosphorus bond breaking is rate-determining. The rate law for the decomposition of CoH(CO)4 to Co2(CO)8 plus hydrogen is second-order in cobalt compound. While this decomposition has previously been studied in the gas phase, this is the first report of decomposition kinetics in the liquid phase. The first step in reaction of Co2(CO)s with organomercury halides is solvent-induced disproportionation of the dimeric carbonyl. ... 

Giese and co-workers " developed a special technique for studying the effects of the substituents upon the relative reactivity of vinyl monomers toward free radicals. Briefly it is as follows. Free radicals are produced by reducing organomercury halides with sodium borohydride. The radicals undergo competitive additions to pairs of various substituted olefins. The adducts in turn are trapped by hydrogen transfers from the formed organomercury hydrides. Relative quantities of each product are then determined ... 

Organomercury halides are accessible by a number of routes (Chapter 2). Generally the Grignard method is quite convenient. The polarizable RHg— group ( soft acid) prefers to bind the heavier halogens (I > Br > Cl), so that if X = Br or I, the product is mainly RHgBr or RHgl. 

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