Stability and structure of Lewis adducts of aluminum hydrides and halides

Abstract

The structures and thermodynamic stabilities of X(YH4)3, X and/or Y being boron or aluminum, were calculated using ab initio molecular orbital methods. The structures were determined at the Hartree-Fock level using the 6-31G* basis set and confirmed to be minima by vibrational analysis. Correlation effects were estimated using MP4(SDTQ) calculations at the Hartree-Fock minima. The correlated energies were used to estimate AH0 and AG°for the decomposition of these dodecahydrides into various products. No Hartree-Fock minimum could be found for B(A1H4)3. The symmetries of the other structures were found to be rotated prisms. Only A1(BH4)3, which is known experimentally, was stable with respect to all the decomposition modes studied. Comparison of the calculated vibrational spectra of these dodecahydrides with those of analogous covalently bonded molecules and ionically bonded molecules suggests that B(BH4)3, A1(BH4)3, and A1(A1H4)3 are all primarily covalently bonded.

Oxygen-Bridged Adducts Formed by Chemical Reactions of Solid Aluminum Halides. Experimental Dilemma and ab Initio Calculations of Heterodimer Complexes AlX3−Y (X = F, Cl; Y = OH-, H2O)

“…[23][24][25][26] They are in good agreement with Al-O distances in neutral Al-H 2 O radical complexes calculated using density functional theory. 41 Due to collective interactions in solids, the same tendency can be observed for Al-O and Al-F (Al-Cl) bond lengths in solid aluminum oxides and halides, respectively.…”

Carbene complexes of Group 13 trihydrides: synthesis and characterisation of [MH3{CN(Pri)C2Me2N(Pri)}], M = Al, Ga or In

“…Such an assumption seems feasible on electronegativity grounds (Cl and Br are more electronegative than H) and if a comparison is drawn with AlH 3 which has quantitatively been shown to be less Lewis acidic than AlCl 3 . 20 Compound 8 was also prepared in moderate yield (38%) by treating ether solutions of LiInH 4 with either 1 or 2 equivalents of I (Scheme 1). In these reactions an insoluble by-product was formed which proved to be too thermally unstable to characterise.…”

Computational Study of Aluminum Chloride Activation for Toluene Chlorination

“…The Al-Cl distance found here for AlCl 3 dissolved in toluene (2.085 Å) is in good agreement with these other studies as is the planar, trigonal geometry that resulted from the current geometry optimization. Wilson et al 17 report unscaled vibrational frequencies at the HF/6-31G* level of 156.6, 213.5, 399.5, and 642.3 cm -1 , whereas Ystenes et al 18 The energetics of Al 2 Cl 6 , HCl-AlCl 3 , and H 2 O-AlCl 3 dissociation have also been reported for gas-phase calculations. In addition, for Al 2 Cl 6 , the heat of dissociation has been estimated from thermodynamic equilibrium data.…”