Lead ll Halides with

S.4.7.2.5. from Lead(ll) Halides with Organomagnesium-Halide Reagents. 

Lead(ll) acetate can be used as an alternative to lead(II) halides with carborane anions, offering advantages in solubility in certain systems. 

From Lead and Methyl Halides. Ordinary forms of lead are not capable of reacting with organic halides to form Pb(CH3)4. However, finely divided lead, e.g., that formed in the reaction of CHgLi with lead(ll) halides, reacts with CH3I giving a quantitative yield of Pb(CH3)4 [15, 252] ... 

From Lead Compounds and Grignard Compounds. The most common laboratory method for synthesis of tetraethyllead is the reaction of a lead(ll) halide, usually PbCl2, with a Grignard reagent in dry ether according to the general equation ... 

Reactions of MC2H5 (M = Li, Na, or K) with lead(ll) halides and other lead(ll) compounds are often conducted in stirred autoclaves with alternate heating and cooling, the reaction product is treated with i-propanol, filtered, washed with water and vacuum-stripped [300, 302, 335, 370, 380]. 

A complex product that can be used for the preparation of Pb(C2H5)4 is obtained upon heating a group 13 metal with a lead(ll) halide and hydrogen in an organic medium under very high pressure [351]. 

The catalytic process is also achieved in the Pd(0)/Cr(ll)-mediated coup-Ung of organic halides with aldehydes (Scheme 33) [74], Oxidative addition of a vinyl or aryl hahde to a Pd(0) species, followed by transmetallation with a chromium salt and subsequent addition of the resulting organochromate to an aldehyde, leads to the alcohol 54. The presence of an oxophile [Ii(l) salts or MesSiCl] allows the cleavage of the Cr(lll) - O bond to hberate Cr(lll), which is reduced to active Cr(ll) on the electrode surface. 

The chemistry of alkynes is dominated by electrophilic addition reactions, similar to those of alkenes. Alkynes react with HBr and HC1 to yield vinylic halides and with Br2 and Cl2 to yield 1,2-dihalides (vicinal dihalides). Alkynes can be hydrated by reaction with aqueous sulfuric acid in the presence of mercury(ll) catalyst. The reaction leads to an intermediate enol that immediately isomerizes to yield a ketone tautomer. Since the addition reaction occurs with Markovnikov regiochemistry, a methyl ketone is produced from a terminal alkyne. Alternatively, hydroboration/oxidation of a terminal alkyne yields an aldehyde. 

Treatment of l,10-distannacyclodeca-2,8,ll,17-tetrayne 100 with electrophiles leads to cleavage of the Sn-C bonds. The reaction of 100 with three different boron halides giving rise to the formation of acetylene derivatives 286 is summarized in Scheme 48 <1997MGM573>. 

However, detailed insights into the electronic transitions of lead-thiolate complexes can be gained from studies on T1(I) [which is isoelectronic with Pb(ll)] and Pb(ll)-doped alkali halides in the solid state (Fig. 5) (37, 50, 54, 113). The details of the electronic transitions in T1(I) doped alkali halides and related compounds have been studied extensively (both theoretically and experimentally) because these compounds have interesting luminescent properties and are useful in phosphors. [We will not discuss the emission spectra of these compounds, as they are not relevant to our discussion of lead-thiolate CT in coordination complexes rather, the reader is directed to several extensive reviews of luminescence in doped alkali halide systems (95, 113, 114).] The characteristic absorption spectra of alkali halides doped with a Tl(l) type ion consist of four bands, known as the A, B, C, and D bands. The A band is at lowest energy, followed by B, C, and D respectively the extinction coefficients of the bands follow the general trend D > C > A > B (Fig. 6) (115, 116). Two weaker bands labeled D and D" are also shown in Fig. 6, which are attributed to the same CT transitions as the main D band (116). In Section II.E, we will... 

The interpretation used to explain the absorption spectra of Tl(l) and Pb(ll) solid-state complexes can also be extended to aqueous solution spectra of Pb(ll) complexes (Fig. 5) (54—60, 62). Although aqueous lead halide absorption spectra reported by Fromherz et al. (54, 55) were not originally interpreted in the context of CT spectroscopy (56, 125), in retrospect it is clear that the bands reported are the same as those observed in doped alkali halide crystals, as are later spectra reported by Bendiab et al. (59, 60). For example, in solution a spectral shift to longer wavelengths is observed for increasing atomic number of the halogen ligand (54, 55), which is consistent with a CT process (126). 

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