Molecular structure of lutetium trichloride monomer and dimer

This paper reports on a simultaneous electron diffraction and mass spectrometric study of the saturated vapor of lutetium trichloride at T = 1070(10) K. It is found that the vapor consists of the monomer LuCl3 [91.6(1.2) mol. %] and dimer Lu2Cl6. The following parameters were obtained for LuCl3 (rg configuration): rg(Lu-Cl) = 2.403(5) A, rg(CL.Cl) = 4.119(18) A,g(Cl-Lu-Cl) = 117.9(1.3)ℴ. Calculation of vibrational corrections for a transition from rg to rα geometry gave a planar equilibrium configuration for LuCl3 with D3h symmetry, whereas our previous electron diffraction study recommended a pyramidal configuration. Possible reasons for this controversy are discussed. The geometry of the Lu2Cl6 molecule of D2h symmetry is described by the following parameters (ra configuration): rα(Lu-Clt) = 2.366(5) A, rα(Lu-Clα) = 2.589(24) A, ZClt-rLu-Clt = 119(7)ℴ, ZClb-Lu-Clb = 84(2)ℴ. The mean energies of the terminal [E(Lu-Clt) = 485 kJ/mole] and bridging [E(Lu-Clb) = 292 kJ/mole] bonds of Lu2Cl26 are estimated.