Synthetic and Structural Investigations of Dinitrogen, Carbonyl, Olefin, Dichloride, and Hydride Derivatives of Bis(Pentamethylclopentadienyl)Titanium and Zirconium

The crystal structures of three compounds containing the (η5 -C5Me5) 2M (M = Ti, Zr) moiety have been determined by single crystal X-ray diffraction methods. (η5 -C5Me5) 2 TiCl2 has a distorted tetrahedral configuration about titanium comprised of the two chlorine atoms and the centroids of the two η5 -C5Me5 rings. Several ring methyl groups are bent considerably out of the cyclopentadienyl plane away from titanium due to chlorine methyl and inter-ring methyl-methyl crowding. The final R factor was 0. 032. The structure of (η5 -C5Me5) 2Ti2N2 consists of two (η5 -C5Me5) 2Ti moieties bridged by N2 in a linear Ti-N≡N-Ti arrangement. The final R index was 0. 058. A qualitative molecular orbital treatment of the bonding consistent with the structure is presented. The structure of (η5 -C5Me5) 2ZrN22N2 consists of two (η5 -C5Me5) 2ZrN2 subunits bridged by a third dinitrogen ligand. Terminal and bridging dinitrogen ligands are bound end-on to zirconium with essentially linear Zr-N≡N and Zr-N≡N-Zr arrangements. The final R factor was 0. 035. A qualitative picture of the zirconium-dinitrogen bonding consistent with the structure and other physical properties of the compound is presented.