The molecular structure of ScI3 and Sc2I6 determined by gas-phase electron diffraction and theoretical studies

The structure of the ScI3 molecule has been studied by synchronous gas-phase electron diffraction and mass spectrometric experiment combined with theoretical studies. The saturated vapour over ScI3 at 896(10) K contained ∼96 and 4 mol% of monomeric and dimeric species, respectively. The following structural parameters of ScI3 have been determined: rg(Sc-I)=2.650(5), rg(I⋯I)=4.530(10) Å, ∠g(I-Sc-I)=117.6(4)°. Quantum chemical investigation of ScI3 and Sc2I6 molecules using DFT and MP2 approaches has been carried out. According to the results of both experimental and theoretical studies the equilibrium geometry of scandium triiodide molecule is planar (D3h symmetry) and the Sc2I6 molecule possesses a structure of D2h symmetry with four Sc-I bridge bonds.