COMPARATIVE-STUDY BY SINGLE-CRYSTAL X-RAY STRUCTURE DETERMINATIONS OF TETRAMETHYLAMINOBORANE AND TETRAMETHYLETHENE AT 110-K

The single crystal structures of the two isoelectronic and isosteric compounds tetramethylaminoborane and tetramethylethene have been determined by an X-ray study at 110 K. The distances of the central bonds are refined to 140.3(1) pm (B=N) and 134.8(1) pm (C=C), the CXXC-torsion angles (XX=CC, BN) are smaller than 1-degrees in both compounds. A bond-length-bond-order correlation for the aminoboranes [(CH3)2N]nB(CH3)3-n with n = 1, 2, and 3 give a regression coefficient of 0.9977, the same is found for the CNC-angle as a function of the CBNC-torsion angle. Also, the comparison among these aminoboranes show that the variation of CBNC-torsion angles has more influence on bond lengths at small angles.