Chemistry of Diborane(4) Derivatives: Mixed Tetraaminodiboranes(4) and Additions of Diborane(4) Derivatives to an Amino‐imino‐borane

Several transamination reactions of B2(NMe2)4 (1a) with secondary amines have led to mixed tetraaminodiborane(4) compounds B2(NMe2)4 - n(NR2)n (2–4), and B2(NC5H10)4 (1d) has been characterized by an X-ray structure analysis which reveals the presence of a rather long B–B bond (1.75 A). However, tetraaminodiboranes(4) of type R2N(Me2N)B-B(NMe2)NR2 are more readily accessible from LiNR2 and B2(NMe2)2Cl2. Similarly, amination of B2(NMe2)2Cl2 with N,N'-dimethylethylenediamine (7) yields B-[bis(dimethyl-amino)boryl]-N,N'-dimethyl-1,3,2-diazaborolidine (8), while reactions with Li(Me)N–CH2–CH2–N(Me)Li (9) lead also to 2,3-bis(dimethylamino)-1,4-dimethyl-1,4,2,3-diazadiborinane (10) as the kinetically controlled product. This is further substantiated by the reaction of the B2(NMe2)2Br2 with 9 which gives exclusively the corresponding 1,4,2,3-diazadiborinane 11. Diborane(4) dihalides B2(NMe2)2X2 (X = Cl, Br) react only in a 1:1 ratio with tmp-B=N-CMe3 (13) leading to 14a, b. However, both a 1:1 and a 1:2 methoxyboration of 13 has been observed with B2(OMe)4 with formation of 15 and 16.