f-block coordination complexes' coordination numbers are difficult to determine in solution,
but by looking at their crystal structures their coordination numbers can be deduced. Because
the f-orbitals aren't available for bonding, and can be said to have a "core" like nature the
geometry of the f-block metal complex is determined by the ligands datively bonded to it rather
than it's electronic structure.
The ligand-ligand interactions reflect the geometry, rather than metal-ligand interactions, this gives rise to distorted complexes being much more common with f-block metals compared to d-block metal complexes.
Author: Sally Robinson, date of modification: 20 March 2003