2‐Boraindane und 2‐(Dialkylamino)1‐2‐benzoborol‐Dianionen

2‐Boraindanes and 2‐(Dialkylamino)1‐2‐benzoborole Dianions ortho1‐Xylene reacts with the Lochmann‐Schlosser base to produce a mixture of the potassium derivatives K2[1,2‐C6H4(CH2)2] (2) and K[2‐MeC6H4CH2] (3). Condensation of 1 + 2 with BCl2(NR2) (RMe, Et, iPr) affords 2‐(dialkylamino)1‐2‐boraindanes (1a–c) (50%). Treatment of 1a, b with LiTMP/TMEDA in THF yields dilithio derivatives [Li(tmeda)]2[C6H4(CH)2BNR2] (8a, b) (40%) which show tripledecked structures consisting of an aromatic 10′‐electron 2‐benzoborole dianion and two [Li‐(tmeda)]+ units facially bound to the borole ring. 1a reacts with HCl/Et2O/hexane to give C6H4(CH2)2BCl · OEt2 (1d · OEt2) (76%) which decomposes in vacuo to give the chloro derivative 1d. The methyl derivative C6H4(CH2)2BMe (1e) is obtained from 1a by treatment with LiMe/Et2O at –78°C and subsequently with HCl/Et2O at –78°C (41%). 1a, b react with MeOH at –78°C to give solid adducts C6H4(CH2)2BOMe · NHR2 (12a, b) while 1c affords C6H4(CH2)2BOMe (1f). Subsequent ring‐opening produces 2‐MeC6H4CH2B(OMe)2 (13). With the exception of 1b the 2‐boraindanes 1 are crystalline solids. The silylation of the 2‐benzoborole dianions and various (2‐methylbenzyl)borane derivatives is also described.