Metal-containing compounds, Silicon

Metal-containing compounds, Silicon Compounds (Continued) 4-Trimethylsilyl-1,3-butadiynyllithium, 180... 

In addition to the types of compounds discussed so far, the group IVA elements also form several other interesting compounds. Silicon has enough nonmetallic character that it reacts with many metals to form binary silicides. Some of these compounds can be considered as alloys of silicon and the metal that result in formulas such as Mo3Si and TiSi2. The presence of Si22 ions is indicated by a Si-Si distance that is virtually identical to that found in the element, which has the diamond structure. Calcium carbide contains the C22-, so it is an acetylide that is analogous to the silicon compounds. 

Contrary to previous reports suggesting colloidal metal as the active species in Pt-catalyzed hydrosilylations, the catalyst was found to be a monomeric platinum compound with silicon and carbon in the first coordination sphere.615 The platinum end product at excess olefin concentration contains only platinum-carbon bonds, whereas at high hydrosilane concentration, it is multinuclear and also contains platinum-silicon bonds. An explanation of the oxygen effect in hydrosilylation was also given to show that oxygen serves to disrupt multinuclear platinum species that are formed when poorly stabilizing olefins are employed. 

Submerged-Arc Furnace. Furnaces used for smelting and for certain electrochemical operations are similar in general design to the open-arc furnace in that they are usually three-phase, have three vertical electrode columns and a shell to contain the charge, but direct current may also be utilized. They are used in the production of phosphoms, calcium carbide, ferroalloys, silicon, other metals and compounds (17), and numerous types of high temperature refractories. 

The reaction of benzaldehyde with various silicon-metal compounds has been studied with interesting results (entries 37, 51, 52). Apparently, insertion with Si-0 bond formation is the first step, followed by loss of a metal-containing fragment. The following stages are proposed... 

Entries 79, 80, and 83- 86 show that the potent reducing agent LiAlH4 cleaves a variety of silicon-metal bonds, giving a hydridosilane. Nucleophilic attack by H is indicated a discussion of the associated stereochemistry is deferred until Section IV,E. When the silicon-platinum compounds shown in entries 85 and 86 are reduced, metallic platinum is formed, but the metal-containing products in other cases have not generally been identified. Equation (63) provides an example of a compound with a robust Si-Fe bond that resists reductive cleavage (237) (cf. Section III,C,3). 

Metal hydroxides in combination with various silicon-containing compounds have been used to reduce the amount of additive required to achieve a required level of flame retardancy in a variety of polymeric materials, including polyolefins.62-63 Systems that have been used contain a combination of reactive silicone polymers, a linear silicone fluid or gum, and a silicone resin, which is soluble in the fluid, in addition to a metal soap, in particular magnesium stearate. However, there is little insight given into how these formulations work. 

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