Metallo self-condensation

Metallo-silanols represent a special class of silanols which is characterized by a remarkably high stability with respect to self-condensation. This property, which is even valid for silanetriol derivatives [2], and the generally stable metal-silicon bond makes these compounds useful precursors for controlled condensation with chlorosilanes to build up unusual arrangements of fimctionalized siloxanes at metal centers. The metal fragment is responsible for highly hydridic Si-H units, creating the conditions for electrophilic oxygenation with DMD [3]. 

Metal-fragment substituted silanols are known to be stable towards self-condensation due to the strongly reduced acidity of the Si-OFI proton [2], However, these species show ready reaction with organochlorosilanes RsSiCl, which gives access to metallo-siloxanes [2], constituting attractive models for transition metal complexes anchored on silica surfaces. 

Recently, it has been demonstrated that transition metal fragment substituted silanols are both stable with respect to self-condensation and reactive towards various chlorosilanes. Due to these properties metallo-silanols provide interesting starting materials for the synthesis of special siloxane arrangements at metal centers [2]. 

Despite their greatly reduced reactivity with respect to self-condensation, the Si(OH) units in the stable bis(metallo)silanols 7a and 8 can be used to carry... 

The transition metal-substituted silanols 5,7 and 8 show the expected reduced tendency towards self-condensation. However, upon treatment with Me2Si(H)Cl in the presence of EtsN, they can be converted into the corresponding bis(metallo)-sUoxanes 9a,b and 10 (Fig. 5), useful for further modifications involving the SiH function [12]. 

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