Reversible insertion

It was also shown in 1983 [11] that lithium can be reversibly inserted into graphite at room temperatures when a polymeric electrolyte is used. Prior experiments with liquid electrolytes were unsuccessful due to co-intercalation of species from the organic electrolytes that were used at that time. This problem has been subsequently solved by the use of other electrolytes. 

The HRTEM observation of the cross section of a coated fiber showed that the core is constituted of aromatic layers highly misoriented, whereas they are preferentially oriented in parallel for the thin coating pairs of stacked layers form mainly Basic Structural Units (BSUs) in which the average interlayer distance is smaller than between the aromatic layers in the bulk of the fiber. Since the nanotexture is more dense for the pyrolytic carbon than for the fiber itself, it acts as a barrier which prevents the diffusion of the large solvated lithium ions to the core of the fiber, allowing the passivation layer to be less developed after this treatment. Hence, the major amount of lithium inserted is involved in the reversible contribution therefore this composite material is extremely interesting for the in-situ 7Li NMR study of the reversible insertion. 

The Cossee mechanism has been demonstrated by direct observation of organometallic complexes where a C = C bond inserts itself into an M-C bond as shown in Eq. (7)-(9). A labeling experiment on a cationic platinum complex 111 indicated the reversible insertion of the coordinated alkene into the Pt-C bond as shown in Eq. (7) [142]. 

Hydrogenation to both formaldehyde and formic acid is catalyzed by K[RuCl(EDTA-H)] [21, 112, 113], but the proposed mechanism involved a highly unlikely reverse insertion of C02 (Eq. (19)). 

A comparison of the probabilities of the events (Table 1) for the catalysts 2 and 6 reveals that the basic difference between them is the reversed insertion regioselectivity the 2,1- insertion is preferred for 2, and the 1,2-insertion - for 6. In both cases the insertions happen only at the primary carbons, and in both cases the isomerization starting from the primary carbon has much lower probability than any insertion. Therefore, it comes as no surprise that the observed number of branches is that low for the system 2, since it is controlled only by the 1,2-/2,1- insertion ratio, as in system 6. However, it is quite surprising and hard to predict without simulations that the average isomerization/insertion ratio and especially the resulting microstructures of the polymers are so different for the two systems. Just because of the reversed insertion regioselectivity ... 

Fig. 2.8 A d irect route to vinylboranes in rhodium-catalyzed hydroborations with phos-phine-free catalysts (including oxidative degradation of a rhodium phosphine). The key intermediate is a rhodium hydride, capable of reversible insertion into the alkene (step A), followed by addition of borane in step B. This leads to reductive elimination of RH in step C followed by boryl migration in step D. A further...

Intercalation refers to a solid state reaction involving reversible insertion of guest species G into a host structure [Hs]. The host provides an interconnected system of accessible unoccupied sites, . The reaction can be schematically represented as... 

As noted above, lithium ions may be reversibly inserted into a variety of carbonaceous materials, according to eq. (7.4). Carbons which have been... 

A recent report also demonstrates reversible insertion of C02 into two of the alkoxy groups in Mo2(OCH2CMe3)6 to yield Mo2(OCH2CMe3)4-(02C0CH2CMe3)2 (154). This contrasts with the reaction of the related dialkylamide complex W2(NMe2)6, which reacts completely with C02 to yield W2(02CNMe2)6. 

Similar reactivity towards phenylisocyanate is found, while carbodiimide yields a 1 1 adduct in which insertion into the M—-OR bond has not taken place.250,251 Copper(II) methoxide undergoes the reversible insertion of C02 to yield the corresponding carbonate.252... 

Reactions like these, where they have been tested, have also proved to be suprafacial on the conjugated system. Thus the reversible insertions of sulfur dioxide into the stereochemically labelled butadienes 2.178 and 2.179 take place stereospecifically, and suprafacially. 

In conclusion, this new class of composites, in which microparticles of Li alloys are encapsulated in rigid matrices such as oxides or carbon (which do not interfere with the reversible insertion of Li and alloying), seems to be highly promising as anodes for rechargeable, high energy density Li batteries. 

Carbon and graphite are used in batteries as electrodes or as additives in order to enhance the electronic conductivity of the electrodes. As electrodes, graphites and disordered carbons reversibly insert lithium, and hence they may serve as the anode material in -> lithium batteries. Graphitic carbons intercalate lithium in a reversible multi-stage process up to LiC6 (a theoretical capacity of 372 mAh g-1) and are used as the main anode material in commercial rechargeable Li ion batteries. As additives, carbon and graphite can be found in most of... 

Palladium-catalyzed vinylations of aryl halides are generally referred to as the Heck reaction (for reviews on the Heck reaction see [34-40]), a versatile process that can be performed inter- and intramolecularly [41]. In the Heck reaction the carbon-carbon single bond forming step is an insertion of an al-kene into the aryl-Pd bond, i.e., a carbopalladation, giving rise to an alkyl-Pd species. If this insertion is terminated by /1-hydride elimination the expected vinylation product is the outcome of the classical Heck reaction. Likewise, reversible insertion of a highly strained olefin where the /1-hydride elimination is suppressed leads to an entry to multiple Pd-catalyzed bond forming processes. 

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