The reactions of NH 3 BH 2 R (R = Me, Ph and Cl) with THFBH 3 have been investigated and it was found that different substituents on the B atom help to proceed the reactions in different ways. The expected doubly-bridged B-substituted aminodiborane products, similar to aminodiborane (ADB, BH 2 (μ-H)(μ-NH 2 )BH 2 ) via the reaction of ammonia borane (AB, NH 3 BH 3 ) and tetrahydrofuran borane (THFBH 3 ), are not obtained. Two competitive reactions occurred with the change of R = Me or Ph. When R is a Me group, an "open" version of B-substituted μ-aminodiborane, THFBH(Me)(μ-NH 2 )BH 3 , is [a]