Silylamines—

Reactions of phosgene at the Si-N bond frequently result in the formation of isocyanates with concomitant cleavage of the Si-Cl moiety, Equation (10.28) [1408a,1409]  

The reactions of phosgene with primary IV-silyl-substituted amines take place at lower temperatures than the corresponding unsilylated amines and, in the case of lower alkyls, the unstable N-silylcarbamoyl chloride intermediate is irreversibly decomposed to the isocyanate at low temperatures, consistent with Equation (10.29)  

In contrast, the corresponding alkyl carbamoyl chlorides are relatively stable, and require the presence of base and temperatures of ca. 100 C in order to undergo dehydrochlorination efficiently [1409]. 

With certain silylated diamines, phosgene reacts to form the corresponding substituted urea. Equations (10.30) (n = 3 or 4) and (10.31) [197a]. However, for longer chains, viz. Me3SiNH(CH3) NHSiMe3 when n = 6, the expected diisocyanate, OCN(CH2)gNCO is formed [2133]. 

iV-disilyl-substituted amines react with COClj at low temperatures (ca. 0 C) to give the corresponding monoisocyanate [1409]  

---

The chlorosilanes are clear Hquids that should be treated as strong acids. They react readily with water to form corrosive HCl gas and Hquid. Liquid chlorosilanes and their vapors are corrosive to the skin and extremely irritating to the mucous membranes of the eyes, nose, and throat. The nitrogen-functional silanes react with water to form ammonia, amines, or amides. Because ammonia and amines are moderately corrosive to the skin and very irritating to the eyes, nose, and throat, silylamines should be handled like organic amines. Trimethylsilyl trifluoromethanesulfonate and trimethylsilyl iodide form very corrosive acidic products. 

These derivatives undergo ready reactions with silylamines ... 

The second preparation for a free iminosilane was found by the Klinge-biel group. It is based on a fluorine/chlorine exchange of lithiated fluoro-silylamines with subsequent thermal LiCl elimination.17... 

Despite some of the melt fabrication problems, the organosiloxane systems produced by the silylamine-hydroxyl reaction ( ) produced interesting, perfectly alternating copolymers. 

It is well known that some silylamines, in combination with haloboranes, provide a facile route to aminoboranes (Equation 1) (26). Meller and Fullgrabe (19.) have previously reported that a... 

Fluorofunctional Silylamines and -Hydrazines -Precursors of (Si-N) Ring Systems... 

Perfluoro-substituted four- and six-membered (Si-N) ring systems (3, 5) can be obtained by reacting dilithiated silylamines with SiF4. Cyclodisilazanes of the type 3 are the smallest known four-membered (Si-N) rings. Transannular Si Si ring distances of 237 pm are found [1,3]. For the first time cyclotrisilazane crystallizes in twist conformation [1]. 

Metallo-silylamines and Metallo-silanimines 3.1 Bifunctional Silylamines... 

Whereas most of the known silylamines containing both a silicon halogen and nitrogen hydrogen unit undergo rapid condensation with HC1 elimination [11], transition metal substitution of the silicon provides unexpected high thermal stability. Compounds of this type are available via reaction of the dichlorosilyl complexes 18a-c with bulky primary amines to generate 19a-c (Eq. (4)). 

Apparently, amines act as Si-nucleophiles toward BENAs (434), and elimination of silylamines (Si N < ) and silanol (from hemiacetals A) affords nitroso-alkenes B as key intermediates of this process. According to the published data (503), a-nitrosoalkenes B react with amines to give the target oximes (453),... 

It has not been shown unambiguously, however, whether the rhodium remains coordinated to the ligands 2 and 3 during the catalysis. Kantam and associates [23] have used a Pd(II) catalyst anchored onto MCM-41/silylamine (MCM-41 a molecular-sieve) for hydrodehalogenation of aryl halides by atmospheric hydrogen. The catalyst was reused for several cycles with constant activity. 

Hydrosilylation of imine compounds was also an efficient method to prepare amines. The hydrosilylation product TV-silylamines can readily be desilylated upon methanol or water treatment, yielding the corresponding amines. The amines can be converted to their corresponding amides by subsequent acyl anhydride treatment. The first attempt to hydrogenate prochiral imines with Rh(I) chiral phosphine catalysts was made by Kagan102 and others. These catalysts exhibited low catalytic activity, and only moderate ee was obtained. 

It has been known for some time that the basicities of a heteroatom decrease upon a-silyl substitution [12], For example, alkyl silyl ethers (R3Si-0-R ) are less basic than dialkly ethers. Silylamines are weak bases compared to alkylam-ines. This electron-withdrawing effect of silyl groups has been explained in terms of the interaction between low lying vacant orbitals such as 3d orbitals of silicon or a orbitals with the nonbonding p orbitals (lone pairs) of the heteroatom (Fig. 4). This interaction decreases the HOMO level which in turn lowers the basicity of the heteroatom. Such effect may also cause the increase of the oxidation potentials, but little study has been reported on the electrochemical properties of this type of compounds. 

Cleavage reactions of the silicon- nitrogen bond of silylamines by TeF6 affords aminotellurium(VI) fluorides (73, 74, 76) as in Eq. (13), where n = 1, 2 ... 

The quantitative nature of the silylamine-phenol reaction has been demonstrated for several different polymer systems (7). In our case, the charged PDMSX content was low to ensure that <1 phenolic group per novolac molecule reacted. This was done primarily to prevent extensive branching or crosslinking, and problems of insolubility and reproducibility associated with network formation... 

No free PDMSX should be found in these systems however, unreacted starting novolac will be present. Hence, each copolymer system consisted of a blend of novolac resin and novolac-PDMSX copolymer. Hie structure of these copolymer systems is complex. Since all phenolic groups possess equal reactivity towards silylamine groups, the difunctional PDMSX may react anywhere between two novolac chains (an A-B-A triblock species) or twice with the same novolac molecule. The second reaction type would yield a macrocyclic compound whose size would depend upon the proximity of the two phenolic groups to one another. 

---