Molecular structure of lutetium trichloride monomer and dimer

This paper reports on a simultaneous electron diffraction and mass spectrom etric 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 (r(g ) configuration): r(g)(Lu-Cl) = 2.403(5) Angstrom, r(g)(Cl . . . Cl) = 4.11 9(18) Angstrom, angle (g)(Cl-Lu-Cl) = 117.9(1.3)degrees Calculation of vibr ational corrections for a transition from r(g) to r(alpha) geometry gave a planar equilibrium configuration for LuCl3 with D-3h symmetry: whereas our previous electron diffraction study recommended a pyramidal configuration. Possible reasons for this controversy are discussed The geometry of the Lu2 Cl6 molecule of D-2h symmetry is described by the following parameters (r(a lpha) configuration): r(alpha)(Lu-Cl-t) = 2.366(5) Angstrom, r(alpha)(Lu-Cl -b) = 2.589(24) Angstrom, angle Cl-t-Lu-Cl-t = 119(7)degrees angle Cl-b-Lu- Cl-b = 84(2)degrees The mean energies of the terminal [E(Lu-Cl-t) = 485 kJ/ mole] and bridging [E(Lu-Cl-b) = 292 kJ/mole] bonds of Lu2Cl6 are estimated .