Öffnung des Aza‐ closo ‐dodecaboran‐Gerüsts durch Basen

Opening of the Aza‐ clso ‐dodecaborane Skeleton by Bases The aza‐ closo ‐borane PhNB 11 H 11 ( 1a ) is opened by the amines NR 3 (R = Me, Et) to give the novel aza‐ nido ‐dodecaboranes PhNB 11 H 11 (NR 3 ) ( 2a, b ). The non‐planar open pentagonal face of 2a, b accomodates the N atom, a BHB bridge, and the base‐bound B atom, according to NMR spectra and the crystal structure analysis of monoclinic 2b . A similar but more symmetric structure is found when closo ‐RNB 11 H 11 ( 1a‐c , R = Ph, Me, H) is attacked by anionic bases X − to give nido ‐RNB 11 H 11 X − ( 3a‐j ; R/X = Me/H, Me/F, Me/Cl, Ph/OH, H/OMe, Me/OMe, Me/OtBu, Me/NEt 2 , Me/Me, Me/Bu). The anions are precipitated with cations [K([18]crown‐6)], [S(NMe 2 ) 3 ], [N(PPh 3 ) 2 ], [Et 2 NH 2 ], or [Li(tmeda) 2 ]. The nido ‐structures of type 2 and 3 are derived from the hypothetical closo ‐NB 12 H 13 .