[ajones51]

For a trigonal bipyramidal complex, ML5, of D3h symmetry, which of the metal d-orbitals are likely to participate in pi bonding?

When I solved the reducible representation for sigma bonding and its component irreducible representation, I found that 2A1' + E' + A2"
For the metal M: the d orbitals (from the character table) are in A'1, E', and E".  How from this information can i determine which of the metal d-orbitals are likely to participate in pi bonding?

Any help would be great.

[FeLiXe]

well if A' and E' are involved in sigma bonding, than it's probably the E"
those are the dxz and dyz orbitals

that is also kind of what you would expect
dz2 sigma bonds with the axial ligands
the two orbitals in the xy-plane sigma bond with the equatorial ligands

dxz and dyz are in between and don't point directly at any ligand