An ab initio study of a germanium-germanium double bond in digermene

Combined Crossed Molecular Beams and Ab Initio Study of the Bimolecular Reaction of Ground State Atomic Silicon (Si; 3 P) with Germane (GeH4 ; X1 A1 )

The chemical dynamics of the elementary reaction of ground state atomic silicon (Si; ³ P) with germane (GeH₄ ; X¹ A₁ ) were unraveled in the gas phase under single collision condition at a collision energy of 11.8±0.3 kJ mol^-1 exploiting the crossed molecular beams technique contemplated with electronic structure calculations. The reaction follows indirect scattering dynamics and is initiated through an initial barrierless insertion of the silicon atom into one of the four chemically equivalent germanium-hydrogen bonds forming a triplet collision complex (HSiGeH₃ ; ³ i1). This intermediate underwent facile intersystem crossing (ISC) to the singlet surface (HSiGeH₃ ; ¹ i1). The latter isomerized via at least three hydrogen atom migrations involving exotic, hydrogen bridged reaction intermediates eventually leading to the H₃ SiGeH isomer i5. This intermediate could undergo unimolecular decomposition yielding the dibridged butterfly-structured isomer ¹ p1 (Si(μ-H₂ )Ge) plus molecular hydrogen through a tight exit transition state. Alternatively, up to two subsequent hydrogen shifts to i6 and i7, followed by fragmentation of each of these intermediates, could also form ¹ p1 (Si(μ-H₂ )Ge) along with molecular hydrogen. The overall non-adiabatic reaction dynamics provide evidence on the existence of exotic dinuclear hydrides of main group XIV elements, whose carbon analog structures do not exist.

New Insight into the Nature of Bonding in the Dimers of Lappert's Stannylene and Its Ge Analogs: A Quantum Mechanical Study

The strength and nature of the connection in Lappert's stannylene dimer ({Sn[CH(SiMe3)2]2}2) and its smaller analogs, simplified stannylenes, as well as similar Ge complexes were studied by means of DFT-D3 calculations, energy decomposition analysis (EDA), electrostatic potential (ESP), and natural population analysis. The trans-bent structure of the investigated molecules was rationalized by means of EDA, ESP, and molecular orbital (MO) analyses. The different ESPs for the monomers studied are a result of different hybridization of the Sn (Ge) atoms. The comparably strong stabilization in the largest and the smallest systems with a dramatically different substituent size is explained by the different nature of the binding between monomers. For all complexes, it has been found that the total attractive interaction is mostly provided by the electrostatic component (>50%), followed by orbital interaction and dispersion. In the largest molecule (Lappert's stannylene), the dispersion interaction plays a more significant role in stabilization and its magnitude is comparable to that of orbital interaction; on the other hand in the smallest molecule (SnH2), where bulky substituents are replaced by H only, the dispersion energy is less important and the E-E bond is more of a charge-transfer character, caused by donor-acceptor orbital interactions. The charge transfer in Ge dimers is greater than in the Sn ones due to shorter distances between monomers, which cause better ⟨HOMO/LUMO⟩ overlaps. The easier dimerization of Lappert's stannylene as compared to Kira's ({Sn[(Me3Si)2CHCH2CH2CH(SiMe3)2-κ(2)C,C']}) stannylene is explained by the different orientation of their substituents-asymmetry promotes dimerization.

Symmetry breaking in the planar configurations of disilicon tetrahalides: Pseudo-Jahn–Teller effect parameters, hardness and electronegativity

The correlations between the Pseudo-Jahn–Teller Effect (PJTE) parameters (i.e. F, Δ and K₀), structural and configurational properties, global hardness and global electronegativities in disilicon tetrahalides were investigated by means of ab initio and hybrid-DFT methods.

Ge3H(n)- anions (n = 0-5) and their neutral analogues: a theoretical investigation on the structure, stability, and thermochemistry

The structure, stability, and thermochemistry of various Ge3H(n)- isomers (n = 0-5) and of their neutral analogues have been investigated at the B3LYP/6-311+G(d), MP2(full)/6-31G(d), and Gaussian-2 (G2) level of theory. For Ge3H(-), both the B3LYP and the G2/MP2 methods predict the cyclic, H-bridged structure 1a- as the global minimum, more stable than another cyclic isomer and an open-chain isomer by ca. 10 and 25 kcal mol(-1), respectively. For Ge3H2(-), the B3LYP and the G2/MP2 methods provide a somewhat different description of the potential energy surface. At the G2/MP2 level of theory, the global minimum is the cyclic, H2Ge-bridged structure 2a-, separated by other three nearly degenerate isomers by ca. 10 kcal mol(-1). On the other hand, at the B3LYP level of theory, the cyclic, H-bridged structure 2e-, not located at the MP2 level of theory, is more stable than 2a- by ca. 1 kcal mol(-1). For Ge3H3(-), both the B3LYP and the G2/MP2 methods predict the cyclic, H3Ge-bridged isomer 3a- as the global minimum, but the energy differences with the other five located isomeric structures predicted by the two methods are quantitatively different. Similar to Ge3H2(-), the B3LYP and the G2/MP2 theoretical levels provide a somewhat different description of the Ge3H4(-) potential energy surface. At the G2/MP2 level of theory, the global minimum is the cyclic structure 4b- of C(2v) symmetry, featuring a Ge2H4 moiety and a Ge-bridged atom, which is more stable than other three located isomers by 3, 9, and 17 kcal mol(-1). On the other hand, at the B3LYP level of theory, the open-chain isomer 4a- of H3Ge-Ge-GeH(-) connectivity is more stable than 4b- by ca. 1 kcal mol(-1) and nearly degenerate with the alternative open-chain isomer H3Ge-GeH-Ge(-). For Ge3H5(-), both the B3LYP and the G2/MP2 methods predict the 2-propenyl-like isomer H3Ge-Ge-GeH2(-) as the global minimum, with energy differences with other four isomeric structures which range from ca. 1-2 to 13-17 kcal mol(-1). At the G2 level of theory and 298.15 K, the electron affinities of Ge3H(n) are computed as 2.17 (n = 0), 2.57 (n = 1), 1.70 (n = 2), 2.41 (n = 3), 2.07/1.80 (n = 4), and 2.71/2.46 eV (n = 5). The two alternative values reported for Ge3H4 and Ge3H5 reflect the alternative conceivable choice for the structure of the involved neutrals and ions. The G2 enthalpies of formation of Ge3H(n) and Ge3H(n)- (n = 0-5) have also been calculated using the atomization procedure. Finally, we have briefly discussed the implications of our calculations for previously performed mass spectrometric experiments on the negative ion chemistry of GeH4.