Atomic interactions in ethylenebis(1-indenyl) zirconium dichloride as derived by experimental electron density analysis

A topological analysis of the experimental electron density in racemic ethylenebis(1-indenyl)zirconium dichloride, C20H16Cl2Zr, measured at 100 (1) K, has been performed. The atomic charges calculated by the numerical integration of the electron density over the zero-flux atomic basins demonstrate the charge transfer of 2.25 e from the Zr atom to the two indenyl ligands (0.19 e to each) and two Cl atoms (0.93 e to each). All the atomic interactions were quantitatively characterized in terms of the electron density and the electronic energy-density features at the bond critical points. The Zr-C2 bond paths significantly curved towards the C1-C2 bond were found; no other bond paths connecting the Zr atom and indenyl ligand were located. At the same time, the pi-electrons of the C1-C2 bond are significantly involved in the metal-ligand interaction. The electron density features indicate that the indenyl coordination can be approximately described as eta(1) with slippage towards eta(2). The 'ligand-opposed' charge concentrations around the Zr atom were revealed using the Laplacian of the electron density and the one-particle potential; they were linked to the orbital representations. Bonds in the indenyl ligand were characterized using the Cioslowski-Mixon bond-order indices calculated directly from the experimental electron density.