Cationic Germanium Fluorides: A Theoretical Investigation on the Structure, Stability, and Thermochemistry of GeFn/GeFn+ (n = 1-3).

The structure, harmonic frequencies, enthalpies of formation, and dissociation energies of the GeFn+ cations (n = 1−3) and of their neutral counterparts GeFn have been investigated at the MP2 and CCSD(T) levels of theory and discussed in connection with previous experimental and theoretical data. The CCSD(T,full)/cc-pVTZ-optimized geometries and MP2(full)/6-311G(d) harmonic frequencies are 1.744 Å and 668.0 cm-1 for GeF(2Π), 1.670 Å and 798.6 cm-1 for GeF+(1Σ+), 1.731 Å/97.4° and 267.0 (a1)/673.1 (b2)/690.6 (a1) cm-1 for GeF2(C2v,1A1), 1.666 Å/116.9° and 202.3 (a1)/769.6 (a1)/834.6 (b2) cm-1 for GeF2+(C2v,2A1), 1.706 Å/112.2° and 214.4 (e)/273.1 (a1)/699.6 (a1)/734.1 (e) cm-1 for GeF3(C3v,2A1), and 1.644 Å and 211.4 (e‘)/229.9 (a2‘ ‘)/757.4 (a1‘)/879.3 (e‘) cm-1 for GeF3+(D3h,1A1). These calculated values are in excellent agreement with the experimental data reported for GeF, GeF+, and GeF2, and should be therefore of good predictive value for the still unexplored GeF2+, GeF3, and GeF3+. The comparison of the CCSD(T,full)/cc-pVTZ enthalpies of formation at 298.15 K, −11.6 (GeF), −125.9 (GeF2), −180.4 (GeF3), 158.4 (GeF+), 134.1 (GeF2+), and 44.8 (GeF3+) kcal mol-1, with the available experimental data, especially for the cations, shows discrepancies which suggest the need for novel and more refined measurements. On the other hand, the computed adiabatic ionization potentials of GeF, 7.3 eV, GeF2, 11.2 eV, and GeF3, 9.7 eV, are in good agreement with the available experimental estimates.