Fourier transform-ion cyclotron resonance study of the gas-phase acidities of germane and methylgermane; Bond dissociation energy of germane

Basis sets developed using the generator coordinate method and a pseudopotential have been adapted to density functional theory to calculate the proton affinity of GeH4, GeH3-, GeF3 -, CH3GeH2 -, and Ge(OH)3 - and the electron affinity of ·GeH3 and ·GeF3. The proton affinity of GeH4 is calculated to be 673.9 kJ mol-1 at 298 K, while values for GeH3 - (1505.0 kJ mol-1) and CH3GeH2 - (1529.0 kJ mol-1) are in excellent agreement with experimental values. The electron affinity of ·GeF3 is predicted to be in the range of 3.5−3.7 eV by calculations using different functionals and ab initio methods. The present calculations reveal that the B3P86 method can yield proton affinities comparable to those obtained with other high-quality methods but consistently overestimates electron affinities of simple Ge radicals.

Section: Resultsmentioning

confidence: 99%

Calculation of the Proton and Electron Affinity of Simple Ge-Containing Species Using Density Functional Theory

Morgon

Riveros

1998

“…The present paper, which reports the completion of the series, examines the effects of protonation and deprotonation on BLs and BDEs of the third-row elements. Motivation for our additional computations is provided by recent experimental studies of the gas-phase basicities and acidities of small arsines, closely related experimental measurements on germane and methyl germane, and accurate theoretical studies of the thermochemical properties of the third-row binary hydrides, GeH 4 , AsH 3 , SeH 2 , and HBr.…”

Section: Introductionmentioning

confidence: 99%

Protonation and Deprotonation Effects on the Chemistry of the Third-Row Elements: Homolytic versus Heterolytic Cleavage

Boyd

1999

Ab initio MO calculations indicate that the effect of protonation of third-row X (X = Ge, As, Se, Br) in CH3XH n , C2H5XH n , C2H3XH n , and C2HXH n is similar to that of first- and second-row X; specifically, both the CX homolytic bond dissociation energies (BDEs) and (except for As and the ethynyl compounds) the CX bond lengths (BLs) increase. Deprotonation decreases the CX BDE for saturated compounds, an electronegativity effect, but increases it for unsaturated ones (except Ge), a resonance effect; correspondingly, the CX BLs increase in saturated and decrease in unsaturated compounds (except Ge). Heterolytic CX dissociation of third-row RCXH n +1 + to RC+ and XH n +1 is often favored over the homolytic process when XH n +1 is electronegative relative to the hydrocarbon moiety (XH n +1 = AsH3, SeH2, BrH); the corresponding dissociation of RCXH n - 1 - to RC- and XH n - 1 similarly may be favored for RC = ethynyl and X n - 1 low in electronegativity (XH n - 1 = GeH2 -, AsH-, Se-). The CC BDEs are also affected by protonation of X; protonation increases the CC BDEs and usually shortens the CC bond, while deprotonation does the opposite.

“…Although the thermochemistry of compounds containing third-row elements, especially the third-row hydrides, has received particular attention in recent years, − information on the intrinsic basicities and acidities of these compounds is very scarce. Only recently have the experimental gas-phase acidities or basicities of GeH 4 , AsH 3 , SeH 2 , and HBr been reported in the literature. − …”

Section: Introductionmentioning

confidence: 99%

Gas-Phase Basicities and Acidities of Ethyl-, Vinyl-, and Ethynylarsine. An Experimental and Theoretical Study

Guillemin

Decouzon²,

Maria³

et al. 1997

Self Cite

The gas-phase basicities and acidities of ethynyl-, vinyl- (or ethenyl-), and ethylarsine have been measured by means of FT-ICR techniques. The structures of the different neutral, protonated, and deprotonated species were elucidated by means of ab initio molecular orbital calculations at the MP2 level. Their final energies were calculated in the framework of the G2 theory. The agreement between calculated and experimental values for both basicities and acidities was fairly good. Protonation of vinylarsine and ethynylarsine at the Cα carbon leads to the breaking of the C−As bond, such that the corresponding protonated species can be viewed as complexes between ethylene and acetylene, respectively, with a AsH2 + cation. More importantly, these complexes are predicted to be as stable as the cations formed by direct protonation at the arsenic atom. For the particular case of ethynylarsine, this result is consistent with the experimental evidence. The gas-phase basicity decreases (GB values decrease) and acidity increases (Δacid G° values decrease) in the following order: ethylarsine, vinylarsine, ethynylarsine. The performance of the B3LYP density functional approach in the description of the thermochemical properties of these arsenic-containing species was also studied.