Silanes Other organosilanes

In this part, we wish to focus on the study of two types of silanes. Aminoorganosilanes are special members of the alkoxysilanes group. They carry the catalyzing amine function, required for chemical bonding with the silica surface, inside the molecule. This makes them more reactive than other organosilanes and reduces the complexity of the liquid phase reaction system to be studied. Only three components, silica, silane and solvent, are present. Furthermore there is a large interest in the reaction mechanism of silica gel with APTS, since this aminosilane is the most widely used compound of the organosilane family. 

The effect of other organosilanes on deteriorated limestone was investigated. Particular attention was paid to the depth of penetration, effects on color, and the degree of consohdation. A solution of acryhc silane in methyltrimethoxysilane was found to be the most suitable consolidants for use on limestone (Bradley, 1987). It was also shown that organosilanes do not encapsulate salt in stone and that soluble salts could be removed by a poulticing technique following consolidation. 

So far, most studies of surface modification of porous AAO membranes have been conducted using silanization, with organosilane compounds covalently bound to the oxide surfaces of AAO membranes. Organosilanes on AAO surfaces can be used to immobilize polymers, proteins, and other molecules for additional functionalization [151, 152]. 

Further studies quickly revealed that the rapid dehydrogenative coupling of primary organosilanes to oligomers and the slower coupling of secondary silanes to dimers can be effected under ambient conditions with compounds of the type CP2MR2 (M = Ti, R = alkyl M = Zr, R = alkyl or H)(11,12,13). None of the other metallocenes, metallocene alkyls, or metallocene hydrides of groups 4, 5 or 6 have shown any measurable activity for polymerization... 

Given the ability of 14 electron fragments [(dtbpm)Pt(O)] and [(dcpm)Pt(O)] to activate C-H and C-Si bonds of inert organosilanes under very mild reaction conditions, it was of course no big surprise that Si-H activation reactions of silanes are possible as well. Hydrido-silyl complexes were formed in practically quantitative reactions if 14 or IS were used as precursors for the [(dtbpm)Pt(O)] fragment. Examples of Si-H insertion products, all stable, isolable compounds which could be fully characterized, are 25 - 27, and others have been made. 

The following sections discuss the organosilane compounds commonly used for conjugation to inorganic surfaces. These reagents and many other silane derivatives are available from a number of commercial sources, which include Dow Corning, Gelest, Aldrich, and others. 

It is possible to use mixtures of organosilanes carrying different head-groups for tailoring of surface properties. By doing so, issues like nonspecific adsorption or crowding of the active surface functionalities can be addressed. In order to find the best surface composition for the immobilization of the ONDs it is necessary to perform systematic studies varying the silane concentrations and other reaction parameters. Examples of this kind of study with mixtures of epoxy- and amine-silanes has been reported recently [33,34]. 

Silanes have also been employed to improve adhesion to metal substrates. For example, Toray Chemicals of Japan has observed adhesion improvement for Mo by employing an organosilane (isopropanol solution) and for Al, Ti, Ni, and Pd by employing an organotitanate spun from toluene. Results for other silanes to Au and Al are reviewed later. Similarly, Dynamit Nobel recommended employing glycidoxypropyltrimethoxysilane to improve positive photoresist image adhesion to Ta, W, Al, and Nb. 

Transition metals have already established a prominent role in synthetic silicon chemistry [1 - 5]. This is well illustrated by the Direct Process, which is a copper-mediated combination of elemental silicon and methyl chloride to produce methylchlorosilanes, and primarily dimethyldichlorosilane. This process is practiced on a large, worldwide scale, and is the basis for the silicones industry [6]. Other transition metal-catalyzed reactions that have proven to be synthetically usefiil include hydrosilation [7], silane alcdiolysis [8], and additions of Si-Si bonds to alkenes [9]. However, transition metal catalysis still holds considerable promise for enabling the production of new silicon-based compounds and materials. For example, transition metal-based catalysts may promote the direct conversion of elemental silicon to organosilanes via reactions with organic compounds such as ethers. In addition, they may play a strong role in the future... 

---