Metal d orbitals in an octahedral crystal field

This series of diagrams illustrate the directionality of the metal d orbitals with respect to ligand σ orbitals, represented as black spheres.

It should be noted the orbitals with e_g symmetry point directly at ligand σ orbitals, whereas the orbitals with t_2g symmetry do not.
The orientation of the five d orbitals with respect to the ligands of an octahedral complex: the degenerate (a) e_g and (b) t_2g orbitals.

d Orbitals in Tetrahedral Crystal Field

Orbital-orbital overlap and SALC Homepage