The parent 1,3,2-diazaboracyclohexane ring systems c-N(H)B(R)N(H)C3H6 (1-4 : R = Ph, Me, i-Pr, t-Bu) were converted to a series of mono- and disilyl derivatives c-N(E)B(R)N(X)C3H6 (5-8 : E = SiMe3; X = H; R = Ph; Me, i-Pr, t-Bu. 9-11 : E = X = SiMe3; R = Ph, Me, i-Pr. 12,13 : E = t-BuMe2Si; X = H, SiMe3; R = Ph) by deprotonation with n-BuLi followed by addition of Me3SiCl or t-BuMe2SiCl. Deprotonation/substitution reactions with chloroboranes, rather than chlorosilanes, afforded several N-boryl derivatives of the Ph-B (1) ring system [14, 15 : E = H; X = B(NMC2)2, B(Ph)NMe2. 16,17 : E = SiMe3; X = B(NMe2)2, B(Ph)NMe2. 18 : E = X = B(BNMe2)2]. Silicon-nitrogen bond cleavage reactions of the N-SiMe3 compounds 5 and 9 with PhBCl2 gave the thermally unstable B-Cl derivatives 19, 20 [E = H, SiMe3; X = B(Ph)Cl] which, in turn, were converted to the B-NMe2 analogs 15 and 17 by reactions with Me3SiNMe2. The more sterically congested diborylamines 12-26 [R = i-Pr, t-Bu; E = H, SiMe3; X = B(NMe2)2, B(Ph)NMe2, B(Ph)OCH2CF3], were prepared from 3, 4, or 7 by similar methods or by dehydrohalogenation reactions. A selective Si-N cleavage reaction of the unsymmetrical disilyl ring system 13 with PhBCl2 afforded the more stable B-Cl derivative 27 [E = t-BuMe2Si; X = B(Ph)Cl]. These new compounds were characterized by multinuclear NMR spectroscopy and elemental analyses. In some cases (15, 17, 18), barriers to rotation about the terminal B-NMe2 bonds were determined by dynamic H-1 NMR spectroscopy.