NEUTRON DIFFRACTION STUDY OF DECABORANE

A three-dimensional neutron diffraction study on an ordered crystal of deuterated decaborane (11B102H14) at -160° has been completed. This is the first investigation of a boron hydride by neutron diffraction, and the accuracy of the Hydrogen atom positions is greaterthan that of any X-ray or electron diffraction study. The molecular structure was found to be consistent with the cap model introduced by Kasper, Lucht, and Harker3 (space group C2/a-C2 with a = 14.23 Å, b = 20.26 Å, c = 5.62 Å, and β = 90.10° at = 160°; Z = 8). The bridging deuteriumatoms are in asymmetric positions with respect to the bonding boron atomsin agreement with earlier X-ray investigations. The average values of the B-H bond lengths are 1.180 Å and 1.298, 1.347 A for the unbridged and bridged hydrogen atoms, respectively. The standard deviations of the bond lengths are 0.004-0.007 Å, and the B-B bond distances and anglesare in good agreement with those determined by X-rays. The data indicate that hydrogen-deuterium atom exchange takes place preferentially at the bridged positions. The coherent neutron scattering length for 11B has been refined in an earlier neutron diffraction experiment at room temperature using a crystal exhibiting somedisorder.The refined value is (0.64 ± 0.01) · 1012 cm. © 1969, American Chemical Society. All rights reserved.