Molecular structure of dimethyldichlorotitanium(IV) by gas-phase electron diffraction, IR and NMR spectroscopies, and density functional theory calculations. Unexpected distortion from tetrahedral coordination geometry

The molecular structure of (CH3)(2)TiCl2 has been determined by gas-phase electron diffraction. The bond distances are Ti-C = 205.8(4) pm and Ti-Cl = 219.6(3) pm, and the valence angles are Cl-Ti-Cl = 117.3(3)degrees, Cl-Ti-C = 108.9(2)degrees, and C-Ti-C = 102.8(9)degrees. The larger valence angles at Ti are thus those spanned by the more electronegative substituents. This is opposite to the trend observed in the main group analogues (CH3)(2-) ECl(2), E = Si, Ge, or Sn. Density functional theory (DFT) calculations with a triple-zeta basis yield an optimal structure in good agreement with experiment. There is nothing in the gas-phase electron diffraction structure, DFT calculations, gas-phase IR spectra, or the NMR spectra of (CH2D)(2)TiCl2 hinting at unusual methyl group geometries or agostic Ti ... H-C interactions.