Reaction of (Me2CH)2NB:NCMe3 with ZX2 [Z = (Me2CH)2NB, MeB, Me2Si, EtMeSi, ClP, BrP, MeP, (Me2CH)2NAs, MeAs; X = Cl, Br] in hexane gave 58-74% (Me2CH)2NBX:N(CMe3)ZX (I; same Z, X). Treating I [Z = (Me2CH)2NB, Me2Si, EtMeSi, (Me2CH)2NP; same X] with Na-K alloy or Li gave 30-73% azadiboriridines II (same Z). I [Z = (Me2CH)2NB, Me2Si; X = Cl] reacted with Li2YPh (Y = P, As) to give 38-81% boretidines III (same Y, Z). Stable iminoborane Me3SiN(CMe3)B:NCMe3 (IV) reacted with ZCl2 [Z = Me2NB, Et2NB, EtB, Me2CHCH2B, Cl2Si, Me2Si, Cl2Ge, Me2Ge, Cl2Sn, Me2Sn, ClSb] in pentane to give Me3SiN(CMe3)BCl:N(CMe3)ZCl (same Z), which upon warming in CHCl3 gave diazaboretidines V (same Z). Treating IV with ZCl2 (Z = ClP, Et2NP, EtP, Me3CP, PhP, ClAs) in hexane, PhMe, or CHCl3 gave V (same Z) directly. Treating V (Z = ClP, ClAs) with RM [R = Me2CH, Me, Bu, (Me2CH)2N, Me3C; M = Li, MgBr, MgI] gave diazaboretidines VI (same R; R1 = Cl) Y = P, As), which when treated with R1M (R1 = Me3CO, Me2N, Me; M = Li, K, MgI, SiMe3) gave VI (same R, R1). 1H, 13C, and 11B NMR spectra are reported for the aminoiminoboranes and heterocycles prepd. from them. The structures of II [Z = (Me2CH)2NB], III [Z = (Me2CH)2NB; Y = P, As], V (Z = Me2Ge), and VI [Y = As; R = (Me2CH)2N; R1 = Cl] were detd. by x-ray crystallog.