Ferrio silanols

Organosilanols are important intermediates in the synthesis of silicones [5]. Among the different approaches to these species [5], the most convenient is the hydrolysis of organochlorosilanes. This reaction can be transfered to ferrio-chlorosilanes, e. g. la-c, which give the corresponding ferrio-silanols 2a-c in high yield, provided an auxiliary base is present (Eq. (1)). 

Si-H functional ferrio-silanols can only be isolated if aryl or bulky alkyl residues are attached to the silicon, as 5a-c demonstrate, obtained according to Eq. (1). 

In contrast, hydrolysis of the methyl derivative, Cp(OC)2Fe-SiMe(H)Cl (Id), yields the corresponding ferrio-silanol, Cp(OC)2Fe-SiMe(H)OH, as a short-lived intermediate identified by means of IR and NMR spectroscopy, which immediately reacts with Id to give the bis(ferrio)disiloxane 6. Conversion of 6 to the fluorine analogue [Cp(0C)2Fe-Si(Me)F]20, characterized by a linear Si-O-Si arrangement [6], is achieved via consecutive H/Cl- and Cl/F-exchange. 

This fact guarantees controlled conversion of C5Me5(OC)2Fe-Si(H)(Me)Cl (lb) via reaction with H2O to the corresponding ferrio-silanol 4a, which shows the expected higher stability with respect to selfcondensation. In the same manner, the ferrio-dichlorosilane C5Me5(OC)2Fe-Si(H)Cl2 (Ic) reacts with two equivalents of water to produce the ferrio-silanediol 4b, to our knowledge the first example of a hydridosilanediol. 

The described metallo-silanols exhibit high stability concerning condensation, however, the OH groups display reasonable reactivity in context with chlorosilanes. These properties can be used to transform the ferrio-silanols 4a, 4b via reaction with trimethylchlorosilane to the ferrio-di- and -trisiloxanes 13a, 13b characterized by a hydrogen substituted a-silicon. In the case of 4b the first siloxane unit is established after one day, the second takes five days (13b). The same reaction pattern can be applied for the generation of the ruthenio-disiloxanes 13c, 13d, resulting fi-om the treatment of the ruthenio-silanols 8c, 8e with Me2Si(R )Cl. 

Synthesis of Polychlorinated Metallo-Siloxanes via Reaction of the Ferrio-Silanol Cp(0C)2SiMe20H (12) with Hexachlorodisiloxane (2a)... 

Summary Condensation of the diastereomerically pure ferrio-silanol... 

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],... 

The condensation of metallo-silanols with organochlorosilanes [4] is a common method of preparing metallo-siloxanes. It has now been applied to gain diastereomerically pure ferrio-siloxanes RS,SR)-3a-c by interaction of the ferrio-silanol (RS,SR)-1 with the organochlorosilanes 2a-c in ether or benzene at room temperature (Eq. 1),... 

Compared with the ferrio-silanol 1, the complex 4b shows a high field shift of the Si NMR resonance (A5 = 11.02 ppm). 

Treatment of the ferrio-silanol 1 with cyclopentadienyltrichlorotitanium 8 yields, under the conditions of Eq. (1), the tris(ferrio-siloxy)-substituted complex 9. In contrast, the analogous reaction of the tungsten-silanols 5a,b does not succeed in the substitution of all chloro atoms, but leads to the incorporation of only two metallo-siloxy groups to give the trinuclear metal complexes 10a,b, irrespective of the molar ratio (Fig. 2). 

In contrast to ferrio-silanols with a direct metal-silicon bond, a modification of the ligand sphere around the metal center of the ferriomethyl-silanol 13a is possible without decomposition. Photo induced CO/PRj (R = Me, Ph) exchange leads to the mono- and bis-phosphane-substituted ferriomethyl-silanols 14a,b, which can be isolated in moderate yields. In addition, 14a,b can be synthesized by EtsN-assisted hydrolysis of the corresponding ferriomethyl-chlorosilanes. ... 

Group 13 Heterosiloxanes Derived from FerriO Silanols... 

Group 4 Heterosiloxanes Derived from Ferrio-silanols... 

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