Theoretical studies on titanium pentafulvene complexes

A series of six titanium pentafulvene complexes are thoroughly investigated using the B3LYP/6-31G(d) level of theory. Excellent agreement with the available structural data is obtained. Relevant structural parameters indicate that a gradual change of the fulvene ligand coordination to the titanium center. Depending on the nature of the exocyclic fulvene substituents dianionic η5, η1-and olefinic η6-coordination modes are found. This behavior is further supported by NBO and AIM population analyses which predict differences in the bond nature meanly of the contacts between titanium and the exocyclic carbon atom. In an excitation study, several theoretical approaches are evaluated against the available recorded UV–Vis spectra of the six complexes. The “best” approach, time-dependant DFT calculations reproduce the experimental UV data reasonably well, although systematically slightly too small values (abut 50 cm−1) are obtained. The other levels of theory are significantly more erratic. It could further be testified that the absorption maxima correspond to a ligand-to-metal charge transfer from the HOMO to the LUMO+1 of the complexes.