The structures, energies, vibrational, and rotational frequencies, and dissociation energy of GeH+5

Abstract

Eight protonated germane structures (GeH+5) were examined in detail using the self-consistent field (SCF), configuration interaction including single and double excitations (CISD), and coupled cluster including single, double, and perturbatively included triple excitations [CCSD(T)] methods in conjunction with a double-ζ plus polarization (DZP) and a triple-ζ plus polarization (including f functions on germanium TZP+f) basis set. The C4v and the D3h isomers are high in energy [84 and 48 kcal mol−1, respectively, relative to the Cs(I) structure at DZP SCF]. Although structure Cs(I) is the global minimum, both Cs structures, where GeH+5 is comprised of a nearly planar germyl cation and a hydrogen molecule, are essentially equal in energy and allow virtually free hydrogen moiety rotation. Complete hydrogen scrambling does not occur, as the energy of the C2v(I) structure [33 kcal mol−1 (TZP+f CCSD)] is higher than the dissociation energy of GeH+5 into GeH+3 and H2 (D0=10 kcal mol−1). D0 of GeH+5 is almost the same as for SiH+5 due to a favorable highest occupied molecular orbital (HOMO) (σH2)−lowest unoccupied molecular orbital (LUMO) (pGe) interaction in GeH+5. The global minimum was characterized by vibrational frequency analyses (up to TZP+f CCSD), and we also report on the rotational constants as well as the proton affinity of germane (156 kcal mol−1).