Unusual Reactivity of a C,N-Chelated Stannylene with Siloxanes and Silanols

The reactivity of stannylene (L-CN)(2)Sn (1), where L-CN is the 2-(N,N-dimethylaminomethyl)phenyl substituent, toward (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), silicon grease, and triphenylsilanol was explored. The reaction of 1 with one equivalent of TEMPO and silicon grease yielded cyclo-[(L-CN)(2)SnOSn(L-CN)(2)OSiMe2O] (6a), whereas the addition of two equivalents of TEMPO afforded cyclo-[(L-CN)(L-CN-O)SnOSiMe2OSiMe2O] (6b), in which the amine nitrogen atom of one of the L-CN ligands is oxidized to N-oxide. The reaction of 1 with one equivalent of TEMPO and subsequent addition of triphenylsilanol gave (L-CN)(2)Sn(OSiPh3)(2) (5), which further reacted with air in a chloroform solution to provide [(L-CN)(L-CN=O)Sn(OSiPh3)Cl] (7), containing one of the chelating L-CN ligands in the corresponding N-oxide form. In contrast, the direct reactions of 1 with one or two equivalents of triphenylsilanol gave rise to the adduct [Sn-(OSiPh3)(2)]center dot C6H5CH2NMe2 (8a) and the salt [C6H5CH2N(H)Me-2](+)[Sn(OSiPh3)(3)](-)(8b), respectively. All compounds were characterized by NMR spectroscopy and by X-ray diffraction. Analogous reactions of 1 with activated silica were shown to yield tin-doped silica, which was characterized by powder X-ray diffraction and various spectroscopic and microscopic techniques.