Electron-Diffraction Study of Diborane and Deuterodiborane

Abstract

The molecular structures of gaseous B₂H₆ and B₂D₆ were determined by the sector‐microphotometer method of electron diffraction. Structural parameters and standard errors for B₂H₆ were r_g(B–B) = 1.775₀±0.003₅ Å; r_g(B–H)_term = 1.196₀+0.008, −0.006 Å; r_g(B–H)_bridge = 1.339₃+0.002, −0.006 Å; and t = 120.5±0.9°. Corresponding parameters for B₂D₆ were 1.771₂±0.003₅ Å; 1.198₀+0.006, −0.005 Å; 1.333₅+0.002, −0.004 Å; and 119.3±0.9°. Root‐mean‐square amplitudes of vibration were also determined. Bridge hydrogen amplitudes exceeded terminal hydrogen amplitudes in conformity with an extension of Badger's rule. Hydrogen amplitudes exceeded deuterium amplitudes in accordance with the difference in reduced mass. Isotope effects on bond lengths were obscured by an unanticipated experimental flaw which influenced results by 1 or 2 parts per thousand.