This type of isomerism arises in heteroleptic
complexes due to different possible geometric
arrangements of the ligands Important examples
of this behaviour are found with coordination
numbers 4 and 6 In a square planar complex of
formula [MX2L2] (X and L are unidentate), the
two ligands X may be arranged adjacent to each
other in a cis isomer, or opposite to each other
in a trans isomer as depicted in Fig 5