Fragmentation substitutive

A novel potentially useful route for the synthesis of metallo-silanols is based on the reaction of metallohydridosilanes with 1,1-dimethyldioxirane [7,8] resulting in the insertion of oxygen into the Si-H bond. This procedure is supplementary to the hydrolysis route, since, in addition to the transformation of the "normal" ferrio-hydridosilanes 9a,b to the silanols 10a,b, it guarantees the formation of chiral 10c, not available by hydrolysis, from "electron rich" phosphine iron fragment substituted 9c (Eq. (2)). 

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]. 

Figure 15.6 Time dependent turnover of the fragments substituted in position a9 (left panel) and g8 (right panel). The turnover vs. time plot is shown for the parent peptide (0) and its Abu (O), DfeGly (A), and TfeGly O substituted analogues.

Although polynuclear alkyne completes are often prepared by reaction of the alkyne with a suitable metal cluster fragment, heteropolynuclear complexes 69 (Scheme 4-38) have been obtained also by isolobal metal fragment substitution, as noted previously [26]. Higher-nuclearity alkyne complexes also can be produced by the addition of various metal carbonyl fragments to a lower-nuclearity alkyne complex [119], A novel entry to heterobi- (and tri-)metallic neutral p-propargyl complexes (e.g., Fe/Mo) via protonation of trinuclear p-Ti, T1 -o-propargyl derivatives 70 was recently described by Wojcicki and coworkers [120,121]. 

Transition Metal Fragment Substituted Silanols of Iron and... 

Transition Metal Fragment Substituted Silanols of Iron and Tungsten - Synthesis. .. 349... 

It is not possible to obtain metal fragment substituted polysiloxanes by controlled self-condensation reactions with an M-Si bond due to their great... 

W. Malisch, H. Jehle, M. Lager, M. Nieger Metal-Fragment Substituted Disilanols" in Organosilicon Chemistry IV From Molecules to Materials (Eds. N. Auner, J. Weis), Wiley-VCH, Weinheim, 1999, pp. 437. 

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