Another type of geometrical
isomerism occurs in octahedral
coordination entities of the type
[Ma3b3] like [Co(NH3)3(NO2)3] If
three donor atoms of the same
ligands occupy adjacent positions
at the corners of an octahedral
face, we have the facial (fac)
isomer When the positions are
around the meridian of the
octahedron, we get the meridional
(mer) isomer (Fig 5