Intermolecular Self-Interactions of the Titanium Tetrahalides TiX₄ (X = F, Cl, Br)

Abstract

Ab initio calculations have been performed on the closed-shell molecules TiX4 and Ti2X8 (X = F, Cl, Br) in order to determine the magnitude and the nature of the intermolecular self-interactions of the titanium tetrahalides. Geometry optimizations have been carried out using an effective core potential basis set with polarization, including the effects of dynamic electron correlation through second-order perturbation theory (MP2). The importance of higher order correlation effects is examined through coupled cluster single-point energy calculations. Basis set effects are investigated using MP2 single-point energy calculations with large allelectron basis sets. Ti2F8 is predicted to be a bound C2h dimer with bridging bonds, lower in energy than the separated monomers by 10.5 kcal/mol. Ti2Cl8 and Ti2Br8 are predicted to be weakly bound dimers whose structures are that of associated monomers with overall D3d point group symmetry. Ti2Cl8 is lower in energy than separated monomers by 4.9 kcal/mol. Transition states have been found that represent paths to halide exchange between monomers supporting experimental evidence for rapid halide exchange in liquid TiCl4 and in mixed systems such as TiCl4/TiBr4. Disciplines Chemistry CommentsReprinted (adapted) 18, 1998. ReVised Manuscript ReceiVed December 21, 1998 Abstract: Ab initio calculations have been performed on the closed-shell molecules TiX 4 and Ti 2 X 8 (X ) F, Cl, Br) in order to determine the magnitude and the nature of the intermolecular self-interactions of the titanium tetrahalides. Geometry optimizations have been carried out using an effective core potential basis set with polarization, including the effects of dynamic electron correlation through second-order perturbation theory (MP2). The importance of higher order correlation effects is examined through coupled cluster single-point energy calculations. Basis set effects are investigated using MP2 single-point energy calculations with large all-electron basis sets. Ti 2 F 8 is predicted to be a bound C 2h dimer with bridging bonds, lower in energy than the separated monomers by 10.5 kcal/mol. Ti 2 Cl 8 and Ti 2 Br 8 are predicted to be weakly bound dimers whose structures are that of associated monomers with overall D 3d point group symmetry. Ti 2 Cl 8 is lower in energy than separated monomers by 4.9 kcal/mol. Transition states have been found that represent paths to halide exchange between monomers supporting experimental evidence for rapid halide exchange in liquid TiCl 4 and in mixed systems such as TiCl 4 /TiBr 4 .

Hydrolysis of TiCl4: Initial Steps in the Production of TiO2

“…Lower level calculations are also in agreement. 49 The Ti-Cl bond distances in TiCl 3 OH, TiOCl 2 , TiOClOH, TiCl 2 (OH) 2 , and TiCl(OH) 3 are predicted to lengthen from that in TiCl 4 with an increase in the number of O atoms and with changes in the number of ligands bonded to the Ti atom. The Ti-Cl bond distance in TiOCl 2 of 2.234 Å calculated 26 at the B97-1/6-311+G(d,p) level is shorter than our CCSD(T)/aVTZ value by ∼0.02 Å.…”

Functional polyisobutylenes via electrophilic cleavage/alkylation

“…Although TiCl 4 provides excellent control over the cleavage/alkylation reaction, with low rate of undesired side‐reactions, such as carbocation rearrangement, it must be used in relatively high concentrations to achieve adequate overall rate of cleavage/alkylation. Moreover, the concentration of Ti 2 Cl 8 dimer, which is the species active in ionization, is governed by an equilibrium that is exothermic in the forward direction, and therefore its concentration decreases with increasing temperature . We expect this to partially or possibly completely offset any rate increases for the overall cleavage/alkylation process that might be achieved by increases in temperature.…”

Electronic Spectra of Ti(IV) in Zeolites: An Ab Initio Approach

“…The calculations were performed using a cubic supercell with side of 16 Bohr radii, in order to minimize interactions among images. A TiÀCl bond length of 2.177 is obtained and compared with the experimental [23] value of 2.170 and with the theoretical [24] result of 2.171 , obtained at the MP2 level. The vibrational harmonic frequencies resulted at 139, 159, 387 and 501 cm…”