Organomagnesium bromides

In the cyclic series several examples, as summarized above, have been provided. The diastereoselectivity, l or u, essentially can be controlled by the choice of the halide in the Grignard reagent and the additive, i.e., employing either organomagnesium bromide with copper(I) bromide and a phosphine, or organomagnesium chloride with copper(I) bromide and chlorotrimethylsilane (see also syn/anti selectivity in Section 1.1.1.2.). 

The structures of three monomeric organomagnesium bromides in which the magnesium center is penta-coordinate have been established in the solid state. These compounds are MeMgBr(THF)(TMEDA) (156) , 9-bromo-9-[(bromomagnesium)methylene]fluorene tris-THF complex (157) and MeMgBr(THF)3 (158) . 

We briefly discussed in an earlier volume the behavior of the isomeric and homologous organomagnesium bromides compared to the organolithium compounds as a means of furthering our understanding of the thermochemistry of the latter species . Here, we will discuss only the magnesium compounds. Discussion of the cycloalkylmagnesium bromides is deferred to a later section in this chapter. 

TABLE 4. Enthalpies of reaction and enthalpies of formation of organomagnesium bromides in ether solution (kJ mol )... 

There are enthalpies of formation for several unsaturated organomagnesium bromides as well as for species that are their saturated counterparts. How do the enthalpies of the formal hydrogenation reaction (equation 10) of the organomagnesium bromides compare with those for the corresponding hydrocarbons ... 

For the preparation of dihydrodiorganosilane which are liquid at 20 °C, gaseous Cl2SiH2 is dissolved in an ether solution of organomagnesium bromide. After 30 min refluxing, the reaction mixture is hydrolysed with aqueous acetic acid (10%). The following compounds are obtained in this way [124] ... 

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