Microwave Spectrum, Structure, and Dipole Moment of 2,4-Dicarbaheptaborane (7)

The microwave spectra of all monosubstituted carbon and boron isotopic forms, and one disubstituted boron isotopic form of 2,4-dicarbaheptaborane(7) have been analyzed. The skeletal boron and carbon atomic coordinates determined from the rotational constants show that the molecule is a pentagonal bipyramid. The two carbon atoms He in the pentagonal base plane and are separated by one boron atom. The two apex boron atoms appear to lie on, or very near the C axis which is perpendicular to the pentagonal base. A molecular-dipole moment of 1.32 +/- 0.03 D is oriented along the planar symmetry axis.