Molecular Structures of EtTiCl<sub>3</sub> and EtTiCl<sub>3</sub>(dmpe) (dmpe = Me<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PMe<sub>2</sub>): New Insights into β-Agostic Bonding
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Gas-phase electron diffraction (GED) results for EtTiCl3 (1) are consistent with a molecular model of Cs symmetry, with the bond distances (ra in Å) 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 ethyl group geometry or agostic Ti···H−Cβ interactions. The geometry of the EtTi fragment is conspicuously different in the diphosphine complex EtTiCl3(dmpe) (dmpe = Me2PCH2CH2PMe2) (2), the crystal structure of which has been redetermined at low temperature (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)° is acute, and the Ti···Cβ distance at only 2.501(2) Å is strikingly short, confirming a β-agostic interaction.
