Composition and structure of aluminum fluorocomplexes in aqueous solutions of hydrogen peroxide and inorganic acids

Kon'shin, V. V.; Chernyshov, B. N.; Ippolitov, E. G.

doi:10.1007/bf00960107

Cited by 1 publication

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“…For example, the chemical shifts of the tetrahedral-coordinated [Al(OC(CF 3 ) 3 ) 4 ] − with various kinds of counter ions in different solvents, range from 38.8 to 33.8 ppm [140–143]. On the other hand, the chemical environment has a significant effect on the small [AlF 6 ] 3− species and fast ligand exchange occurs in aqueous solutions [148,149]. The solid-state MAS NMR studies found the isotropic chemical shifts of [AlF 6 ] 3− range from −0.1 to −17.9 ppm for which the counter ions include H + , K + , NH 4 + and Rb + [150].…”

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confidence: 99%

Errors in the Calculation of 27Al Nuclear Magnetic Resonance Chemical Shifts

Wang

Zhao

2012

IJMS

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Computational chemistry is an important tool for signal assignment of 27Al nuclear magnetic resonance spectra in order to elucidate the species of aluminum(III) in aqueous solutions. The accuracy of the popular theoretical models for computing the 27Al chemical shifts was evaluated by comparing the calculated and experimental chemical shifts in more than one hundred aluminum(III) complexes. In order to differentiate the error due to the chemical shielding tensor calculation from that due to the inadequacy of the molecular geometry prediction, single-crystal X-ray diffraction determined structures were used to build the isolated molecule models for calculating the chemical shifts. The results were compared with those obtained using the calculated geometries at the B3LYP/6-31G(d) level. The isotropic chemical shielding constants computed at different levels have strong linear correlations even though the absolute values differ in tens of ppm. The root-mean-square difference between the experimental chemical shifts and the calculated values is approximately 5 ppm for the calculations based on the X-ray structures, but more than 10 ppm for the calculations based on the computed geometries. The result indicates that the popular theoretical models are adequate in calculating the chemical shifts while an accurate molecular geometry is more critical.

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