Gold-mercury bonds

The development of the second class of compounds with gold-mercury bonds, that is, Hg-containing, Au-rich clusters, was mainly the contribution of Pignolet and coworkers [41-43]. Such compounds were generally obtained by addition of mercury... 

The reaction of [PPN][Au2 CH2P(S)Ph2 2] with HgCl2, followed by T1PF6 treatment, resulted in a rearrangement of the Au-C bonds and compound 6 was isolated. It is an isomer of compound 5 in the cation of which both gold and mercury are linearly coordinated by a carbon and a sulfur atom. The isomers 5 and 6 do not interconvert under reflux inTHF [36]. The transannular gold-mercury distance in the cation of 6 [2.989(1) A] is about 0.1 A shortest than in the cations containing the... 

Hg[Mn(CO)5]2i with manganese-mercury bonds, is obtained from [Mn (00)5] and mercury(II) cyanide and has already been discussed. A very stable compound with a manganese-gold bond has been obtained by the reaction between Na[Mn(CO)5] and (C6H5)3PAuCl 162)... 

As seen above, compounds of the type R2Fe(CO)4 with iron-carbon a bonds are known only when R is a perfluoroalkyl radical or a maleoyl radical. However, compounds of this type where the iron atom is a-bonded to an element other than carbon, are somewhat more common. Derivatives are known in which the iron atom is cr-bonded to gold, mercury, tin, and lead. 

Gold-mercury cluster compounds have been obtained by different groups. Fackler et al. first prepared two Au-Hg-bonded complexes 143 and 145 in 1988 (Scheme 12.42) [97]. The two complexes are isomeric and the Au-Hg bond lengths are 3.088(1) and 2.989(1) A, respectively. Compound 144 could also be converted into 146 by treating with Au(THT)Cl (THT = tetrahydrothiophene) without T1 salt. The solid structure of 146 showed the Hg-Au distances of 3.310(1) and 3.361(1) A. 

The behavior of Hg(CN)2 toward the dinuclear gold(I) amidinate complexes requires comment. In the case of the dinuclear gold(I) ylide, oxidation of the Au(I) to Au(II) resulted in the formation of a reduced mercury(O) product. Figure 1.19(a) [36]. In the mercury(II) cyanide reaction with the dinuclear gold(I) dithiophosphinate. Figure 1.19(b), the stability of the gold(I)-carbon bond compared... 

This class of compounds showing explosive instability deals with heavy metals bonded to elements other than nitrogen and contains the separately treated groups GOLD COMPOUNDS LEAD SALTS OF NITRO COMPOUNDS LITHIUM PERALKYLURANATES MERCURY COMPOUNDS METAL ACETYLIDES METAL FULMINATES METAL OXALATES PLATINUM COMPOUNDS PRECIOUS METAL DERIVATIVES SILVER COMPOUNDS... 

Action of ammonia or ammonium salts on gold chloride, oxide or other salts under a wide variety of conditions gives explosive or fulminating gold [1], Of uncertain composition but containing Au—N bonds, this is a heat-, friction- and impact-sensitive explosive when dry, similar to the related mercury and silver compounds [2]. In an attempt to precipitate finely divided gold from its solution in aqua regia... 

Each central naked Ag1 or Tl1 atom in [M TR(bzim) 2]BF4 is bonded to six Au1 centers forming a distorted trigonal prism (Fig. 28a) with Au- -M distances ranging from 2.731(2) to 2.922(2) A or from 2.9711(7) to 3.0448(7) A, respectively, indicative of appreciable metal-metal interaction. In the case of the mercury(II) derivative, the Hgn atoms interact with the Au1 centers in adjacent rings (four Au- -Hg contacts in each sandwich) with Hg---Au distances 3.2749(6) and 3.6531(6) A. Lastly, in the TCNQ derivative the cyanide groups are clearly not coordinated to the gold atoms and the distance from the centroid of the TCNQ to the centroid of the Au3 unit is 3.964 A. 

It has been a major point of interest in the study of small metal particles to determine the precise point (if indeed there is a precise point) at which metallic character is lost. The broader context of this problem as it relates to other metals such as mercury and sodium has been discussed in a series of important papers by Peter Edwards and his associates.135,136 The difficulty seems to be that there is no agreed criterion by which membership of the metallic state can be judged, and various physical techniques give somewhat different answers because they sense slightly different aspects of electron behaviour. The question has been earnestly addressed in the case of gold, partly because of the familiar sensitivity of catalytic activity to particle size as noted above (Section 2.1) the way in which electrons are used to form metallic bonds determines the character of the free valences at the surface, and hence the kind of chemisorption bond that is formed with the reactants. 

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