Tetrahedranes. A Theoretical Study of Singlet E4H4 Molecules (E = C to Pb and B to Tl)

Gernot Frenking (1)

1 Fachbereich Chemie

Quantum chemical calculations using DFT (B3LYP) and ab initio (CCSD(T)) methods have been carried out to elucidate the E4H4 singlet potential energy hypersurface for the group-13 and group-14 elements. The results show that there are numerous E4H4 energy minima for the compounds of group-13 and group-14 elements. This holds particularly for the heavier atoms. The classical Td tetrahedron structure is energetically more favourable for the group-13 compounds E4H4 where the tetrahedron isomers are energy minima for all elements E except for thallium. The tetrahedranes Al4H4 1Al and Ga4H4 1Ga are the global energy minima on the singlet PES while 1B is slightly less stable than the singly hydrogen-bridged planar form 12B which has a rhombic B4 core. The lowest-lying energy minima for In4H4 and Tl4H4 are tetrahedranes where the E4 core is face-bridged by the hydrogen atoms. The classical Td tetrahedron structure of the group-14 elements is only for carbon and silicon an energy minimum at B3LYP/def2-TZVPP. The latter form of Si4H4 is a third-order saddle point at BP86/def2-TZVPP and MP2/def2-TZVPP. The global energy minimum form for C4H4 is the vinylideneacetylene isomer 27C which is -63.7 kcal/mol lower in energy than the tetrahedrane.

Mots clés: Physical Sciences

Gernot Frenking. Tetrahedranes. A Theoretical Study of Singlet E4H4 Molecules (E = C to Pb and B to Tl). Molecular Physics, 2009, 107 (08-12), pp.911-922. ⟨10.1080/00268970802680505⟩. ⟨hal-00513247⟩