Koordinationseigenschaften der isolobalen phosphaniminato-und cyclopentadienyl-liganden in TiCl₃(NPH₃), TiCl₃Cp, ReO₃(NPH₃) und ReO₃Cp

The phosphoraneiminato and cyclopentadienyl complexes TiCl₃(NPH₃) (1), ReO₃(NPH₃) (2), TiCl₃Cp (3), and ReO₃Cp (4) have been investigated quantum chemically at the BP86/TZ(2)P level of nonlocal density functional theory (DFT). The metal-ligand bonds turn out to dissociate homolytically with the computed values for the corresponding bond dissociation energies amounting to 79.6 (1), 103.4 (2), 58.1 (3) and 45.0 (4) kcal/mol. Whereas the M-N-P unit in the titanium complex 1 is linear, we find a bent structure for the corresponding rhenium complex 2 (〈 Re-N-P = 136.4°). It turns out that the potential energy surface of the phosphoraneiminato complexes is extremely shallow with respect to the M-N-P angle; a variation over 50° is associated with an energy change of less than 2 kcal/mol. Furthermore, we have carried out a detailed analysis of the bonding in our model complexes to elucidate the difference in metal-ligand bond strengths between the isolobal phosphoraneiminato and cyclopentadienyl ligands.