Molecular Structures of EtTiCl3 and EtTiCl3(dmpe) (dmpe = Me2PCH2CH2PMe2): New Insights into b-Agostic Bonding.
Gas-phase electron diffraction (GED) results for EtTiCl3 (1) are consistent with a mol. model of Cs symmetry, with the bond distances (ra in .ANG.) Ti-C = 2.090(15), C-C = 1.526(11), and Ti-Cl = 2.195(3) and the valence angles (in deg) ?TiCC 116.6(11) and ?ClTiC = 104.6(4). These structural parameters give no hint of an unusual Et group geometry or agostic Ti...H-Cb interactions. The geometry of the EtTi fragment is conspicuously different in the diphosphine complex EtTiCl3(dmpe) (dmpe = Me2PCH2CH2PMe2) (2), the crystal structure of which was redetd. at low temp. (105 K) by x-ray diffraction without the problems of pronounced disorder described in an earlier report. Here the TiCC valence angle at 84.57(9) Deg is acute, and the Ti...Cb distance at only 2.501(2) .ANG. is strikingly short, confirming a b-agostic interaction.
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