Silanes, Stannanes, and Germanes

It should be mentioned here that nucleophilic titanium carbene complexes, generated in situ from dithioacetals and Cp2Ti[P(OEt)3]2 (see e.g. Sections 3.2.2.1 and 3.2.4.2), can undergo M-H insertions with silanes, germanes and stannanes [694]. This reaction represents an interesting alternative procedure for the che-... 

Alkynyl(trimethyl)silanes, germanes, and stannanes produce alkynyl-(phenyl)-A3-iodanes via ligand exchange on iodine under similar conditions [36]. Stang and co-workers developed a useful procedure for the preparation of diverse /3-functionalized alkynyl-A3-iodanes, which involves a ligand exchange of cyano-A3-iodane 19 with alkynylstannanes [37]. 

This outcome is rational since the (/ )-allylsilanes 74 and 75 are expected to exist in conformation 78 (Scheme 11), in which the C-Si bond overlaps with the Jt bond. This conformation maximizes the ct-tc interaction between the C-Si bond and the 7t system84 (see also later section on allylsilanes). Attack of the electrophile from the opposite face to the trimethylsilyl group in 78 gives the carbenium ion intermediate 79, which is stabilized by a interaction with the C-Si bond substituent12,37,38 loss of silicon from this intermediate gives the E olefin products. Anti selectivity has also been observed in the trifluoroacetolysis of 2-cyclohexenyl-silanes, germanes, and stannanes.85... 

TABLE 64. Comparison of molar conductivities (A) of solutions of (O—M)-bis-chelate bis(lactamomethyl)silanes, -germanes and-stannanes in CH2CI2 at 25 °c494 504 893... 

Reported examples include the alkylation of 1,2- and 1,4-dicyanobenzene with toluene [43], amines [44], alkenes [45], silanes, germanes and stannanes... 

Boranes, alanes, silanes, germanes and stannanes, and their substituted derivatives,... 

Silane, germane, and stannane can be synthesized by the reduction of a variety of silicon, germanium, or tin compounds with active metal hydrides. The general method described below, involving the lithium hydroaluminate (LiAlHi) reduction of silicon tetrachloride and tin (IV) chloride, is convenient for the eflficient preparation of 1-50 mmoles of silane and stannane. The method is easily adapted to the synthesis of the deuterio compounds, i.e., silane-d4, germane-dt, and stannane-d4, by... 

A.W. POTTS and W.C. PRICE, The photoelectron spectra of methane, silane, germane and stannane. Proc. Roy. Soc. Lond., A326, 165 (1972). 

VIBRATION AND ROTATION IN SILANE, GERMANE AND STANNANE AITO THEIR MONOHALOGEN DERIVATIVES, Hans Biirger and Annette Rahner... 

Organic tin hydrides carrying three organic groups can also be added smoothly at 70-80° to unsaturated organometallic derivatives of elements of the fourth main Group, such as vinyl-silanes, -germanes, and-stannanes, e.g. 440... 

A carbon-heteroatom bond can likewise be fragmented under these conditions (see Scheme 6). Convenient substrates are silanes, germanes, and stannanes " as well as isoelectronic boron derivatives (as in the cleavage of benzyltriphenylborates after oxidation to the corresponding radical). ... 

Aluminum chloride isopropyl halide HalogenO Silanes, -germanes, and -stannanes by C-cleavage... 

Reactions of potassium hypersilylchalcogenolates with SiCU, GeCU and SnCU yielded the tetrasubstituted silanes, germanes and stannanes despite four sterically demanding substituents (Eq. 3). The NMR data are summarized in Table 2. 

The electrophilic substitution of aromatics by allyl-silanes, -germanes, and -stannanes has been achieved by an in situ transformation to the allyl cationic species (107) with thallium(iii) trifiuoroacetate. This represents a reactivity umpolung of these conventionally nucleophilic reagents, and gives allyl-substituted aromatics in good yield." ... 

Allylic silanes, germanes, and stannanes have been found to fragment smoothly in the presence of various acceptors, leading to the aUylation of ketones, " imminum salts, and aromatics. > ... 

Tetralkyl-silanes, -germanes, and -stannanes, as well as disilanes and distannanes, have been successfully used as alkyl radical precursors. The use of alkyl radicals is closely parallel to that presented above starting from ketals for the substitutive alkylation of aromatics and the conjugate addition to alkenes and alkynes (see Equations 4.5 and 4.28). Notice, however, that the final result depends on the sensitizer-trap used. Thus, N-methylacridinium perchlorate is reductively alkylated by hexamethyldisilane but undergoes reductive dimerization with the corresponding digermanes and distannanes. "... 

Nakanishi, K., Mizuno, K., and Otsuji, Y., Photosubstitution of dicyanobenzenes by aUyKc silanes, germanes, and stannanes via photoinduced electron transfer. Bull. Chem. Soc. Jpn., 66,2731,1993. 

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