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The reaction of the (dichloromethyl)oligosilanes R(Me 3 Si) 2 -SiCHCl 2 4a−d (4a: R = Me; 4b: R = tBu; 4c: R = Ph; 4d: R = SiMe 3 ) with 8-(dimethylamino)-1-naphthyllithium leads to the intramolecularly donor-stabilized silenes 1a−d. Whereas 1a,b, and d were isolated as thermally stable yellow crystalline compounds, 1c could not be separated in a pure form but was characterized by NMR spectroscopy and mass spectroscopy as well as by its chemical reactivity with a variety of substrates. Dynamic 1 H NMR spectroscopic studies of 1a and 1d revealed coalescence of the signals of the two CSiMe 3 groups. In agreement with theoretical calculations, this effect was interpreted as the result of internal rotations about the silene double bond. These findings and the known relatively

Two intramolecularly donor-stabilized silenes, 1-(8-dimethylamino-1-naphthyl)-1,2,2-tris(trimethylsilyl)silene (6a) and 1-(2-dimethylaminomethylphenyl)-1,2,2-tris(trimethylsilyl)silene (6b), were synthesized according to a novel one-step process by the reaction of (dichloromethyl)tris(trimethylsilyl)silane (1) with a twofold molar excess of 8-dimethylamino-1-naphthyllithium or 2-(dimethylaminomethyl)phenyllithium, respectively. Compounds 6a and 6b are thermally stable compounds. X-ray structural analyses of both silenes revealed strong donor-acceptor interactions between the dialkylamino groups and the electrophilic silene silicon atoms (Si-N distances: 6a: 1.751(3) A; 6b: 1.749(3) A) that lead to pyramidalization at the silicon centers. In contrast, the configuration at the silene carbon atoms was found to be planar. The Si=C distances (6a: 1.751(3) A; 6b: 1.749(3) A) fit with literature data of comparable compounds. Addition of water or methanol to the Si=C bonds of 6a,b afforded the silanols 7a,b and the methoxysilanes 8a,b, respectively. The compound 1-(8-dimethylaminomethyl-1-naphthyl)-1,2,2-tris(trimethylsilyl)silene (6c), generated following the same procedure by the reaction of 1 with 8-(dimethylaminomethyl)-1-naphthyllithium (molar ratio 1:2) proved to be unstable at room temperature and underwent rapid insertion of the Si=C group into a methylene C-H bond of the dimethylaminomethylnaphthyl ligand to afford the 1-silaacenaphthene 9.