Quantum Crystallography and Complementary Bonding Analysis of Agostic Interactions in Titanium Amides

Agostic interactions involving titanium are textbook examples for C-H bond activation. Therefore, it is surprising that there is no study in the literature in which the hydrogen atom in the C-H center dot center dot center dot Ti interaction has been determined reliably, although nearly all the criteria for assessing the strength and character of the agostic interaction depend on the hydrogen atom and its position. Here, we demonstrate with quantum crystallographic techniques how hydrogen atoms in a series of three titanium amides can indeed be localized accurately and precisely based on routine single-crystal X-ray diffraction data. Once the hydrogen positions have been established, theoretical and experimentally fitted bonding analyses reveal that the C-H center dot center dot center dot Ti interaction becomes stronger with increasing inter-ligand London dispersion stabilization of bulky alkyl groups.