Transition structures for H2 elimination from XH4 hypervalent species (X = S, Se and Te). Ab initio MO study

Ab initio MO calculations on the fragmentation of hypervalent XH₄ (X = Se and Te) to XH₂ and H₂ show that the most favorable transition structure is highly polarized with C₁ symmetry, which can be viewed as a trigonal bipyramid where one apical and one equatorial ligand are coupled. The least-motion C_2v transition state previously obtained theoretically is much higher in energy.