Silicon dihalides

Between 1965 and 1969, there were rapid developments in the use of other high temperature species, particularly the silicon dihalides (22-23). boron monofluoride (24), boron atoms (25). silicon atoms (26), and alkali metal atoms (27-28). in reactions at liquid nitrogen temperatures. Clearly this experimental method had to be applied to... 

TABLE 23. Standard enthalpies of formation (AHf°/kJmol ) of silicon dihalides... 

Silicon dibromide and diiodide, SiBr2 and Sil267, can both be prepared by passing the tetrahalides SiX4 over elemental silicon (cf. Figure 5). A schematic radical cation state correlation of all silicon dihalides (scheme 13) based on the SiCl 20 sequence [scheme... 

All members of group 14 exhibit an oxidation state of +4, but the +2 oxidation state increases in stability as the group is descended. Carbenes exemplify the C(II) state but exist only as reaction intermediates, silicon dihalides are stable only at high temperatures, the Ge(II) and Sn(II) states are well established, and Pb(II) is more stable than the Pb(IV) state. In this respect, Pb resembles its periodic neighbours, T1 and Bi, with the inertness of the 6 electrons being a general feature of the last member of each of groups 13, 14 and 15 (see Box 12.3). 

Equation (12)) <92CL339>. Coupling the appropriate di-Grignard reagent with the appropriate silicon dihalide was also employed to prepare (163) and (164) in 2% and 1% yields, respectively <87JGU1925, 88JGU429>. The crystal and molecular structures have been reported of 18-membered... 

Reaction of organometallic dihalides with the title dilithio reagent afforded silicon and tin metallaindenes (equation 33)96. 

Halides of aluminum, silicon, and phosphorus5, tin tetrachloride, titanium tetrachloride, and antimony pentachloride6 did not form complexes with diphenyl tellurium oxide, but converted it to the corresponding diphenyl tellurium dihalide. 

---