Beschreibung:
<jats:p>2,4-Dicyclopropyl-1,3-diduryl-1,3-dihydro-1,3-diborete (1 e) has the most strongly deshielded ring carbon atoms (δ<jats:sup>13</jats:sup>C = 186.7 ppm) and the longest C 1–C3 distance (196.6(5) pm) observed so far for 1,3-dihydro-1,3-diboretes. Its folding angle along the C 1–C 3 bond, however, is only slightly reduced (δ = 45°). For the planar (α = 0) unsubstituted 1,3-dihydro-1,3-diborete (1 f′) the corresponding data are calculated by the combined ab initio/IGLO/NMR method to be δ<jats:sup>13</jats:sup>C = 302 ppm and C 1–C3 218.3 pm. Comparison of these data with those of 1 a and 1 b shows that the bonding 1,3-interaction in 1 e is strongly reduced.</jats:p>