Gas‐phase chemistry of ionized and protonated GeF₄: a joint experimental and theoretical study

Abstract

The gas-phase ion chemistry of GeF(4) and of its mixtures with water, ammonia and hydrocarbons was investigated by ion trap mass spectrometry (ITMS) and ab initio calculations. Under ITMS conditions, the only fragment detected from ionized GeF(4) is GeF(3)(+). This cation is a strong Lewis acid, able to react with H(2)O, NH(3) and the unsaturated C(2)H(2), C(2)H(4) and C(6)H(6) by addition-HF elimination reactions to form F(2)Ge(XH)(+), FGe(XH)(2)(+), Ge(XH)(3)(+) (X = OH or NH(2)), F(2)GeC(2)H(+), F(2)GeC(2)H(3)(+) and F(2)GeC(6)H(5)(+). The structure, stability and thermochemistry of these products and the mechanistic aspects of the exemplary reactions of GeF(3)(+) with H(2)O, NH(3) and C(6)H(6) were investigated by MP2 and coupled cluster calculations. The experimental proton affinity (PA) and gas basicity (GB) of GeF(4) were estimated as 121.5 ± 6.0 and 117.1 ± 6.0 kcal mol(-1), respectively, and GeF(4)H(+) was theoretically characterized as an ion-dipole complex between GeF(3)(+) and HF. Consistently, it reacts with simple inorganic and organic molecules to form GeF(3)(+)-L complexes (L = H(2)O, NH(3), C(2)H(2), C(2)H(4), C(6)H(6), CO(2), SO(2) and GeF(4)). The theoretical investigation of the stability of these ions with respect to GeF(3)(+) and L disclosed nearly linear correlations between their dissociation enthalpies and free energies and the PA and GB of L. Comparing the behavior of GeF(3)(+) with the previously investigated CF(3)(+) and SiF(3)(+) revealed a periodically reversed order of reactivity CF(3)(+) < GeF(3)(+) < SiF(3)(+). This parallels the order of the Lewis acidities of the three cations.

Gas-Phase Ion Chemistry of the Noble Gases: Recent Advances and Future Perspectives

“…274 It is, however, of interest to note here that, while Si + , SiH + and SiH 2 + are totally unreactive toward Ar, Kr and Xe, 229 XeCF + and XeCF 2 + cations could be observed by collisions of Xe + with fluorinated selfassembled monolayer surfaces. [275][276][277] The gas-phase reactions of GeF 3 + and GeF 4 H + , recently investigated by IT-MS and theoretical calculations, 230,278 showed numerous similarities with those observed previously for SiF 3 + and SiF 4 H + . In particular, as with SiF 4 H + , GeF 4 H + reacts with Xe 230 and undergoes the ligand displacement reaction described by Equation (5): F 3 Ge-FH + + Xe ® F 3 Ge-Xe + + HF (5) Based on theoretical calculations, the ionic product was unambiguously assigned as the trifluorogermylxenon cation F 3 Ge-Xe + .…”

Germyl Cations with Ge–S Bonds: An Experimental and Theoretical Study on the Gaseous FnGe(SH)+3–n (n = 0–2)

“…The precursor ion is GeF 3 + , a strong Lewis acid able to react whith hydrocarbons, water, ammonia and hydrogen sulfide to form F 2 Ge(Nu) + , FGe(Nu) 2 + and Ge(Nu) 3 + (Nu = C m H n , OH, SH, NH 2 ). As highlighted in our previous studies, 21,22 along the series F n Ge(Nu) + 3-n (Nu = OH, NH 2 ; n = 0-2), the Lewis acidity of the cations and their reactivity toward H 2 O or NH 3 progressively reduces and this trend parallels a decreased group electronegativity passing from F to OH and NH 2 . The electronegativity of SH is still lower than F and, in fact, the presently investigated F 2 Ge(SH) + and FGe(SH) 2 + revealed less acidity and less reactivity toward H 2 S than GeF 3 + .…”

“…43 The potential energy diagrams of reactions (1)-(3), shown in Figure 5, closely resemble those obtained for the strictly analogous reactions involving H 2 O and NH 3 . 21,22 The obtained data point, in fact, to the initial formation of an encounter complex, which undergoes the eventual loss of HF, passing through two consecutive isomerizations. The connectivities and main bond distances of the involved intermediates and TSs are shown in Figure 6.…”

“…10,[18][19][20] The latter route is especially valuable to access homo-and hetero-substituted ions which are not attainable from the ionization of eligible neutrals. In particular, we recently found 21 that GeF 3 + (obtained, in turn, from ionized GeF 4 14 ) is the precursor of novel and otherwise elusive germyl cations, obtained by the consecutive reactions described by the equations GeF 3 + + NuH ® F 2 Ge(Nu) + + HF F 2 Ge(Nu) + + NuH ® FGe(Nu) 2 + + HF FGe(Nu) 2 + + NuH ® Ge(Nu) 3 + + HF Observed species include the Ge-C ions F 2 Ge(C 2 H) + , F 2 Ge(C 2 H 3 ) + and F 2 Ge(C 6 H 5 ) + (NuH = C 2 H 2 , C 2 H 4 , C 6 H 6 ), the Ge-N ions F 2 Ge(NH 2 ) + , FGe(NH 2 ) 2 + and Ge(NH 2 ) 3 + (NuH = NH 3 ) and the Ge-O ions and F 2 Ge(OH) + , FGe(OH) 2 + and Ge(OH) 3 + (NuH = H 2 O). The structure, properties and mechanisms of formation of these species were also assayed by theoretical calculations.…”

“…The structure, properties and mechanisms of formation of these species were also assayed by theoretical calculations. 21,22 As a continuation of these studies, we explored the conceivable occurrence of the above reactions for NuH = H 2 S. Gaseous cations with Ge-S bonds are, in fact, already known, [23][24][25] but germyl cations with such connectivities are still uncovered. We could thus observe F 2 Ge(SH) + ,…”