Mercury alkyls complexes

A number of organometallic compounds show promise for LCEC study, and a few have already been examined in detail (especially mercury alkyls) [9]. More highly conjugated organic compounds such as a,a-unsaturated ketones and imines are occasionally good candidates, but at this time UV detectors frequently outperform electrochemical detectors for such systems. At this writing there have been only a few reported LCEC studies of metal ions or metal complexes. Perhaps the major reason for this is that very little modern LC has been carried out on them using any detector. It is difficult to compete with atomic spectroscopy techniques for the determination of most elements, but as speciation becomes more important, it seems likely that more LCEC methods will be developed for metal complexes. 

Aromatic ketones arylations, 10, 140 asymmetric hydrogenation, 10, 50 G—H bond alkylation, 10, 214 dialkylzinc additions, 9, 114-115 Aromatic ligands mercuration, 2, 430 in mercury 7t-complexes, 2, 449 /13-77-Aromatic nitriles, preparation, 6, 265 Aromatic nucleophilic substitution reactions, arene chromium tricarbonyls, 5, 234... 

Bis(alkyl) complexes, with mercury, preparation, 2, 428 Bis(alkylidene)s, in Ru and Os half-sandwiches, 6, 583 Bis(alkylimido) complexes, with chromium(VI), 5, 346 Bis(rj2-alkyne)platinum(0) complexes, preparation, 8, 640 Bis(alkynyl) complexes in [5+2+l + l]-cycloadditions, 10, 643 with manganese, 5, 819 with mercury, preparation, 2, 426 mononuclear Ru and Os compounds, 6, 409 with platinum, 12, 125 with platinum(II), 8, 539 with titanium(IV), 4, 643 with zirconium, 4, 722... 

Transmetallation is a more convenient method to obtaining divalent organolanthanide complexes from lanthanide metals. Reaction of lanthanide metal powder with a mercury alkyl or aryl complex affords the corresponding divalent lanthanide complex (Equation 8.28) [94]. The preparation of divalent perfluorophenyl lanthanide complexes Ln(C6F5)2(THF) (Ln = Eu, n = 5 Ln = Yb, n=4) is a typical example. In most cases, the addition of a small amount of Lnl3 leads to acceleration of the reaction [95]. 

In reductive acylation and dimerization, the cathode is often superior to dissolving metal or radical anions reductants. So a, j6-unsaturated ketones or esters can be acylated in high yield to 1,4-dicarbonyl compounds at the mercury cathode [39], but the corresponding reaction with sodium in tetrahydrofuran (THE) fails [40]. On the other hand, reductive acylation of double bonds becomes possible in high yield, when vitamin Bj2 is used as mediator [41]. Here cobalt-alkyl complexes play a decisive role as intermediates. 

Organomercurials can also be used for the synthesis of alkyl complexes. Organomercurials have stable alkyl-mercury bonds, and the alkyl groups can be transferred to transition metal complexes (alkylation of the transition metal complexes). Thus diphenylmercury reacts with one equivalent of dichloroplat-inum complex to produce phenylmercuric chloride and monosubstituted platinum complex in good yield 73). 

Vinyl complexes are typically prepared by the same methods used to prepare aryl complexes. Vinyl mercury compounds, like aryl mercury compoimds, are easily prepared (by the mercuration of acetylenes), and are therefore useful for the preparation of vinyl transition metal complexes by transmetallation. The use of vinyl lithium reagents has permitted the s rnthesis of homoleptic vinyl complexes by transmetallation (Equation 3.35). Reactive low-valent transition metal complexes also form vinyl complexes by the oxidative addition of vinyl halides with retention of stereochemistry about the double bond (Equation 3.36). Vinyl complexes have also been formed by the insertion of alkynes into transition metal hydride bonds (Equation 3.37), by sequential electrophilic and nucleophilic addition to alkynyl ligands (Equation 3.38), and by the addition of nucleophiles to alkyne complexes (Equation 3.39). The insertion of alkynes into transition metal alkyl complexes is presented in Chapter 9 and, when rearrangements are slower than insertion, occurs by s)m addition. In contrast, nucleophilic attack on coordinated alkynes, presented in Chapter 11, generates products from anti addition. 

Organic compounds such as terminal alkynes can undergo direct mercuration using various mercury salts. For instance, alkyne 61 has been shown to react with Hg(OAc)2 to form the symmetrical bis-alkyl-mercury complex 62 (Equation (21)).73... 

A common synthetic method is that of equation (9), where X = MeC02,168 PhS03,169 NO3170 or C104,171 and relies on the precipitation of silver chloride. A variation of this method is the synthesis of the ring complex (5), by the reaction (10).172 In other cases, the synthesis may involve mercury(II) salts or sodium salts (equations 11 and 12).173,174 Another useful synthetic method involves reaction of alkyl- or aryl-gold(I) complexes with carboxylic acids or acid anhydrides (equations 13-15).176,177... 

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