The molecular structures of LaCl3 and LaBr3 reinvestigated by gas-phase electron diffraction

The molecular structures of lanthanum trichloride and tribromide have been reinvestigated. The synchronous gas-phase electron diffraction and mass spectrometric experiments were carried out at different effusion cell temperatures. The following thermal average structural parameters were determined (internuclear distances in A ° , bond angles in degrees): rg(La–Cl)Z2.589(6), rg(Cl/Cl)Z4.409(19), :g(Cl–La–Cl)Z116.7(12) at 1295(10) K for lanthanum trichloride; rg(La–Br)Z2.738(6), rg(Br/Br)Z4.636(18), :g(Br–La–Br)Z 115.7(11) at 1095(10) K and rg(La–Br)Z2.747(6), rg(Br/Br)Z4.626(19), :g(Br–La–Br)Z114.8(11) at 1180(10) K for lanthanum tribromide. The experimental data for LaCl3 molecule do not contradict the planar equilibrium structure. The equilibrium configuration of LaBr3 molecule is estimated to be planar. q 2004 Elsevier B.V. All rights reserved