Organoborierung von Tetrakis(trimethylsilylethinyl)stannan – Röntgenstrukturanalyse eines 5‐Stannaspiro[4.4]nona‐1,3,6,8‐tetraen‐Derivates[1]

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Abstract
Organoboration of Tetrakis(trimethylsilylethynyl)stannane – X‐ray Structure of a 5‐Stannaspiro[4.4]nona‐1,3,6,8‐tetraene DerivativeTetrakis(trimethylsilylethynyl)stannane (1) reacts with non‐cyclic trialkylboranes BR3 [2, R = Me (a), Et (b), Pr (c), iPr (d)] and 9‐alkyl‐9‐borabicyclo[3.3.1]nonanes[2e (alkyl = Et), 2f (alkyl = neopentyl)] to give the 3,8‐dialkyl‐2,7‐bis(dialkylboryl)‐1,4,6,9‐tetrakis(trimethylsilyl)‐5‐stannaspiro[4.4]nona‐1,3,6,8‐tetraenes 5a to f in high yield. The reaction proceeds stepwise, and intermediates as well as final products were characterized by 1H, 11B, 13C, 29Si, 119Sn NMR spectroscopy. According to an X‐ray structure analysis of 5f · 0.5 CH2Cl2 (space group P2/c) the endocyclic CSnC bond angles are small [84.9(2) and 84.2(2)°] and the two five‐membered rings are not exactly planar. Steric crowding causes a strong twist of the skeleton of the other ring systems. The agreement between solid‐state and liquid‐phase NMR data shows that main structural features are retained in solution.

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