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

Abstract

The reactivity of stannylene (L^CN)₂Sn (<b>1</b>), where L^CN is the 2-(<i>N,N</i>-dimethylaminomethyl)­phenyl substituent, toward (2,2,6,6-tetramethylpiperidin-1-yl)­oxyl (TEMPO), silicon grease, and triphenylsilanol was explored. The reaction of <b>1</b> with one equivalent of TEMPO and silicon grease yielded <i>cyclo</i>-[(L^CN)₂SnOSn­(L^CN)₂OSiMe₂O] (<b>6a</b>), whereas the addition of two equivalents of TEMPO afforded <i>cyclo</i>-[(L^CN)­(L^CNO)­SnOSiMe₂OSiMe₂O] (<b>6b</b>), in which the amine nitrogen atom of one of the L^CN ligands is oxidized to N-oxide. The reaction of <b>1</b> with one equivalent of TEMPO and subsequent addition of triphenylsilanol gave (L^CN)₂Sn­(OSiPh₃)₂ (<b>5</b>), which further reacted with air in a chloroform solution to provide [(L^CN)­(L^CNO)­Sn­(OSiPh₃)­Cl] (<b>7</b>), containing one of the chelating L^CN ligands in the corresponding N-oxide form. In contrast, the direct reactions of <b>1</b> with one or two equivalents of triphenylsilanol gave rise to the adduct [Sn­(OSiPh₃)₂]·C₆H₅CH₂NMe₂ (<b>8a</b>) and the salt [C₆H₅CH₂N­(H)­Me₂]⁺[Sn­(OSiPh₃)₃]⁻ (<b>8b</b>), respectively. All compounds were characterized by NMR spectroscopy and by X-ray diffraction. Analogous reactions of <b>1</b> with activated silica were shown to yield tin-doped silica, which was characterized by powder X-ray diffraction and various spectroscopic and microscopic techniques