For MLLL, a total of five geometric isomers and six stereoisomers are possible. 
# One isomer in which all three pairs of identical ligands are trans
# Three isomers in which one pair of identical ligands (L or L or L) is trans while the other two pairs of ligands are mutually cis. 
# Two enantiomeric pair in which all three pairs of identical ligands are cis. These are equivalent to the Δ vs Λ isomers mentioned above.
The number of possible isomers can reach 30 for an octahedral complex with six different ligands (in contrast, only two stereoisomers are possible for a tetrahedral complex with four different ligands). The following table lists all possible combinations for monodentate ligands:
Thus, all 15 diastereomers of MLLLLLL are chiral, whereas for MLLLLL, six diastereomers are chiral and three are not (the ones where L are trans). One can see that octahedral coordination allows much greater complexity than the tetrahedron that dominates organic chemistry. The tetrahedron MLLLL exists as a single enantiomeric pair. To generate two diastereomers in an organic compound, at least two carbon centers are required.