No abstract

The initial steps of the reaction of TiCl 4 with CH 3 OH and its isotopomers have been investigated using matrix isolation with infrared spectroscopic detection of the reaction intermediates. When twin jet deposition was employed, a substantial yield of a 1:1 adduct was observed. However, when merged jet deposition was employed with a 15 cm merged reaction region, no traces of the precursors or the 1:1 complex were observed. Rather, very intense bands due to previously unreported monomeric Cl 3 TiOCH 3 were observed, as well as bands due to HCl. Band assignments were assisted by extensive isotopic labeling and supported by density functional calculations. In subsequent experiments, heating the merged region to as high as 350°C led to complete destruction of the bands to Cl 3 TiOCH 3 while bands due to CH 3 Cl and the complex of CH 3 Cl with HCl were observed to grow.

Gas phase hydrogen bonding was studied via infrared spectroscopy in the following systems: methyl acetatehydrogen chloride, methyl formate-hydrogen chloride, 2-butanone-hydrogen chloride, and acetone-hydrogen chloride. The intensity of the H-Cl stretching vibration was monitored as a function of temperature, and the hydrogen bond energies and enthalpies were determined. The hydrogen bond energy for all four complexes was within 2.0 kJ mol -1 of -18.3 kJ mol -1 , indicating that the hydrogen bond energy is only minimally affected by nonlocal molecular structure. The acetone-hydrogen chloride complex was modeled by ab initio methods. The energy of formation of the complex, calculated at the MP2/6-311++G** level of theory, is -20.8 kJ mol -1 , in good agreement with the experiment.

The 1:1 complexes of TiCl4 with PH3 and AsH3 have been characterized in argon matrices. Intense spectral features in the 400−500 cm-1 region were assigned to Ti−Cl antisymmetric stretching modes in each complex, shifted from the parent mode near 500 cm-1, while the bending modes of coordinated PH3 and AsH3 shifted 15−70 cm-1. The Ti−Cl stretching modes of the complexes shifted with different bases; these shifts correlate with the intrinsic basicity of each base.

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