The hydroboration of aryl- and alkylnitrile derivatives using thexylborane leads to the formation of associated aldiminoborane dimers. The reactions occur at room temperature in common solvents such as THF or toluene and the products have been characterized using multinuclear 1D and 2D FTNMR, FTIR, GCMS, and X-ray crystallography.  The products are stable in air and show no decomposition during aqueous workup under ambient conditions.  Initial studies involving the purification and separation of the isomers resulted in a low temperature separation of the major isomer in the syntheses involving the arylnitrile derivatives.  Single crystal X-ray analysis of the compound [p-MeO-C₆H₄-C(H)=N-BH(C(CH₃)₂CH(CH₃)₂]₂ indicates the first example of a structurally characterized dimer with a trans-syn geometry which is consistent with ¹H NMR studies of all purified dimers in solution.