Balázs Réffy

Gallium tribromide: Molecular geometry of monomer and dimer from gas-phase electron diffraction

Abstract The molecular geometry of gaseous gallium tribromide has been determined by electron diffraction augmented with quadrupole mass spectrometry and quantum chemical calculations. Of the two experiments, at the higher temperature (638 K) only the monomeric form was present whereas at the lower temperature (357 K) the monomers and dimers were present in comparable amounts. The monomer is planar with bond lengths ( r g ) 2.239 ± 0.007 A at 357 K and 2.249 ± 0.005 A at 638 K. The dimer has a halogen-bridged structure with bond lengths ( r g ) of 2.250 ± 0.006 A and 2.453 ± 0.005 A and bond angles ∠ a Br b GaBr b 92.7 ± 0.3° and ∠ a Br t GaBr t 123.1 ± 1.4°.