An improved synthesis of B3 (NMe& (2), B4 (NMe& (l), and B6 (NMe& (4) is reported. From each compound two of the four terminal dimethylamino groups are readily replaced by halogen atoms yielding a, o-dihalides B,(NMe2) nX2 (n= 3, 4; X= C1, Br, I). These are used in turn to replace the substituent X by groups like RO, RS, RHN, R2P, and R. Crystal structure determinations on several of these compounds reveal as a common feature ...