Exchange at Silicon

This process, shown as mode 2 in Fig. 2, involves the production and reaction of functionally substituted silyl and silanediyl species. Since this occurs while the silicon-metal bond remains intact, it is not surprising that most of the entries in Table XII relate to compounds with robust Si-Mn and Si-Fe bonds other examples involve bonds to Cr, Mo, W, Re, Pt, and even Co. The types of exchange reaction observed will be dealt with in turn. 

Reaction (72) proceeds sequentially to form mono-, di-, and trisub-stituted products, and can conveniently be followed by H-NMR spectroscopy (Fig. 3). 

Other reagents useful in special cases are PCI5 (entry 14) and heated HCl (entry 5) in the latter case, hydrogen is evolved. 

Chlorine or bromine attached to silicon can readily be exchanged for fluorine by such reagents as AgBF4, HF-I-BF3, or AgPFe, as in entry 10  

This particular reaction was first carried out in the hope that it would lead via Cl abstraction to a cationic species (XXII), as shown in reaction (75) this may be regarded as either a substituted silicenium 

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Lewis base adducts, 25 63, 65-67 ligand exchange at silicon, 25 60-62 mass spectra, 25 99-100 optical activity, 25 101-102 silicon migration, 25 78 ferrasilacyclopentane, 25 9, 22, 34 fluxionality, 25 93, 97 infrared spectra, 25 91-92... 

Ligand exchange at silicon, while the Si-M bond remains intact. 

Recently we have demonstrated that the ferrio-silanol (RS,SR)-l is available, starting either from the diastereomerically pure ferrio-chlorosilane (i / ,5 -Cp(OC)(Ph3P)Fe-Si(Me)(Cl)(Ph) or the ferrio-silane (R5,Si )-Cp(OC)(Ph3P)Fe-Si(Me)(H)(Ph). In both cases, the transformation to the ferrio-silanol 1 - Cl/OH-exchange at silicon or insertion of oxygen into the Si-FI bond using dimethyldioxirane - occurs stereospecifically [3],... 

Chloride exchange at silicon in the chlorosilane (4) has been studied by n.m.r. spectroscopy. This proved a doubly useful technique in this situation. 

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