Several new alkylchloro-and alkyl (dimethy1amino)[bis (trimethylsilyl) amino] boranes,(Me3Si), NB (R) X [X= C1 (R= t-Bu, i-Pr, CH2SiMe3); X= t-Bu (R= CH2SiMe3); X= NMez (R= Me, CH2SiMe3, i-Pr, t-Bu)], have been prepared from (Me3Si) 2NBC12 by chloride displacement with organometallic reagents and Me3SiNMe2. Rotational barriers (AG,'= 17.3-20.9 kcal/mol) about the B-NMe2 bonds were determined by dynamic'H NMR ...