Low spin complex of d^6 -cation in an octahedral field will have the following energy ( _o= . crystal field splitting energy in an octahedral field, P= electron pairing energy)

Step-by-step solution

( C.F.S.E. =(-0.4 x+0.6 y) _o+z P ) where ( x = ) number of electrons occupying ( t _ 2 g ) orbital (y= ) number of electrons occupying (e_g ) orbital (z= ) number of pairs of electrons For low spin ( d ^6 ) complex electronic configuration ( aligned & =t_ 2 g ^6 e_g^0 or t_ 2 g ^ 2,2,2 e_g^0 & x=6, y=0, z=3 & C.F.S.E. =(-0.4 6+0 0.6) _o+3 P & = -12 5 _o+3 P aligned )