Thus, for d
4 (Cr
2+, Mn
3+), d
5 (Mn
2+, Fe
3+), d
6 (Fe
2+, Co
3+)
cases, a vacant pair of d orbitals results only by pairing of 3d electrons
which leaves two, one and zero unpaired electrons, respectively The magnetic data agree with maximum spin pairing in many cases,
especially with coordination compounds containing d
6 ions However,
with species containing d
4 and d
5 ions there are complications [Mn(CN)6]
3–
has magnetic moment of two unpaired electrons while [MnCl6]
3– has a
paramagnetic moment of four unpaired electrons