Silicon—iron bonds

Based on a work by Ruiz et al., who showed that it is possible to generate silicon-iron bonds electrochemically when using dicarbonylcyclopentadienyliron dimer (Fpa) and MesSiCl as... 

Silicon carbide is comparatively stable. The only violent reaction occurs when SiC is heated with a mixture of potassium dichromate and lead chromate. Chemical reactions do, however, take place between silicon carbide and a variety of compounds at relatively high temperatures. Sodium silicate attacks SiC above 1300°C, and SiC reacts with calcium and magnesium oxides above 1000°C and with copper oxide at 800°C to form the metal silicide. Silicon carbide decomposes in fused alkalies such as potassium chromate or sodium chromate and in fused borax or cryolite, and reacts with carbon dioxide, hydrogen, air, and steam. Silicon carbide, resistant to chlorine below 700°C, reacts to form carbon and silicon tetrachloride at high temperature. SiC dissociates in molten iron and the silicon reacts with oxides present in the melt, a reaction of use in the metallurgy of iron and steel (qv). The dense, self-bonded type of SiC has good resistance to aluminum up to about 800°C, to bismuth and zinc at 600°C, and to tin up to 400°C a new silicon nitride-bonded type exhibits improved resistance to cryolite. 

Optically active organometallic compounds, especially pseudotetrahedral half-sandwich complexes of the type Cp(OC)(Ph3P)Fe-R with iron as the center of chirality have been extensively investigated in the past. However, synthetic utilization of stereocontrol by the chiral iron has been limited to systems with a-bonded carbon ligands [2]. In contrast, silicon-iron complexes have not yet found analogous application. In context with our studies concerning metallo-silanols we have established simple routes to isolate diastereomerically pure derivatives with a chiral iron fragment. 

However, several catalytic reactions had been proposed to occur by a mechanism involving metal-silicon double bonds. - Kumada reported oligomerization of disilanes (Equation 13.33), and Ojima reported the scrambling and oligomerization of silanes in the presence of Wilkinson s catalyst (Equation 13.34), and both processes were proposed to occur by silylene intermediates. The formation of a silylene complex of iron tetracarbonyl was claimed in 1977 (Equation 13.35), but this compoimd was never isolated. Since the first structural data reported in 1987, a variety of metal-sUylene complexes have been prepared that are stabilized by coordination of a Lewis base to the silicon of the silylene complex, as in Equation 13.35. The first base-free silylene complex was reported by Tilley... 

A similar process to that shown in Scheme 8 also involves formation of a carbanionic cyclopentadienyl carbon centre. But in this case, silicon-carbon bond formation stems from the migration of a silylmethyl group, which proceeds with rearrangement, as shown in Scheme 9. These surprising rearrangement processes are observed with iron and with tungsten compounds as shown in equations 32 and 33. 

A silica gel containing 3-imidazole propyl groups bonded to surface atoms of silicon has been prepared (253), and was treated 254) with a solution of Fe(TPP)L2, where L = py or pip, where upon the iron(II) porphyrin became attached to the imidazole groups on the surface of the gel,... 

The structure of 22b (Fig. 2) shows a nearly ideal staggered conformation of the silicon and iron fragment with a Si-N bond distance of 1.735 A indicating rc-interaction and the largest angle at silicon formed by the iron and o-toluyl ligand (115.6°). 

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