Metal‐Promoted Cage Rearrangements in the Tricarbollide Series: Conversion of Ligand Derivatives 7‐L‐ nido ‐7,8,9‐C 3 B 8 H 10 (L = H 3 N, t BuH 2 N, Me 2 HN) into Neutral 8‐R‐ nido ‐7,8,9‐C 3 B 8 H 11 (R = H 2 N, t BuHN, Me 2 N) Compounds

Deprotonation of the eleven‐vertex tricarbaborane zwitterions 7‐L‐ nido ‐7,8,9‐C 3 B 8 H 10 [ 1 : L = H 3 N ( 1a ), t BuH 2 N ( 1b ), Me 2 HN ( 1c )], followed by reactions with metal reagents [FeI 2 , NiCl 2 , and Ni(C 5 H 5 ) 2 ] at higher temperatures and in situ acidification, led to the 7 ⇄ 8 rearrangement of the N ‐substituted cage carbon atom to yield a series of 8‐amino‐substituted derivatives of nido ‐7,8,9‐C 3 B 8 H 12 . These were characterized as 8‐R‐ nido ‐7,8,9‐C 3 B 8 H 11 [ 2 : R = H 2 N ( 2a ), t BuHN ( 2b ), Me 2 N ( 2c )]. A possible rearrangement mechanism for their formation has been proposed. Deprotonation of compound 2a with proton sponge [PS = 1,8‐bis(dimethylaminonaphthalene)] generated the [8‐ t BuHN‐ nido ‐7,8,9‐C 3 B 8 H 10 ] − ( 2b − ) anion, which can be reprotonated to give the original compound 2b and not the tautomeric zwitterion 8‐ t BuH 2 N‐ nido ‐7,8,9‐C 3 B 8 H 10 ( 3b ). All compounds were characterized by high‐field ( 11 B and 1 H) NMR and IR spectroscopy, and mass spectrometry. The molecular structures of the neutral carbaborane 2b and its salt PSH + 2b − were determined by single‐crystal X‐ray diffraction analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)