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-ph ase electron diffraction. The bond distances are Ti-C = 205.8(4) pm an d Ti-Cl = 219.6(3) pm, and the valence angles are Cl-Ti-Cl = 117.3(3)d egrees, Cl-Ti-C = 108.9(2)degrees, and C-Ti-C = 102.8(9)degrees. The l arger valence angles at Ti are thus those spanned by the more electron egative substituents. This is opposite to the trend observed in the ma in group analogues (CH3)(2-) ECl(2), E = Si, Ge, or Sn. Density functi onal theory (DFT) calculations with a triple-zeta basis yield an optim al structure in good agreement with experiment. There is nothing in th e gas-phase electron diffraction structure, DFT calculations, gas-phas e IR spectra, or the NMR spectra of (CH2D)(2)TiCl2 hinting at unusual methyl group geometries or agostic Ti ... H-C interactions.