Electron diffraction study of the structure the NbBr4 molecule

The structure of the NbBr₄ molecule is studied in synchronous electron diffraction and mass spectrometry experiments. Gaseous niobium tetrabromide is synthesized in the course of the experiment during the interaction of niobium chips with bromine at 496°C. Analysis of the geometrical models of the NbBr₄ molecules of C_2v, C_3v, D_2d, and T_d symmetries shows that the tetrahedral model is preferable. The thermally averaged parameters of the effective configuration of the NbBr₄ molecule are as follows: r_g(Nb?Br)=2.418(5) Å, l(Nb?Br)=0.074(2) Å, r_g(Br?Br)=3.921(16) Å, l(Br?Br)=0.271(12) Å, δ(Br?Br)=0.027(18) Å.