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

The
reactivity of stannylene (LCN)2Sn (1), where LCN 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-[(LCN)2SnOSn­(LCN)2OSiMe2O] (6a), whereas the addition
of two equivalents of TEMPO afforded cyclo-[(LCN)­(LCNO)­SnOSiMe2OSiMe2O] (6b), in which the amine nitrogen atom of one of
the LCN ligands is oxidized to N-oxide. The reaction of 1 with one equivalent of TEMPO and subsequent addition of
triphenylsilanol gave (LCN)2Sn­(OSiPh3)2 (5), which further reacted with air in
a chloroform solution to provide [(LCN)­(LCNO)­Sn­(OSiPh3)­Cl] (7), containing one of the chelating LCN 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]·C6H5CH2NMe2 (8a) and the salt [C6H5CH2N­(H)­Me2]+[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.