High and low spin 

Assignment of an octahedral's electron configuration of complex includes (i) finding the d electron number of the ion and (ii) determining the occupation of the t₂g and e_g orbitals. Electron repulsion influences are significant, and another things being equal the ground state will be created with the greatest number of electrons in dissimilar orbitals and with parallel spin. Two and three d electrons will take place the t₂g orbitals with parallel spin, but with four or more there are dissimilar possibilities. If the additional repulsion coming from spin-pairing is large sufficient, the ground state will be of the high-spin type created through keeping electrons in separate orbitals as far as possible. Alternatively, if Δ_o is larger than the spin-pairing energy, the facilitate configuration will be low-spin created through

placing as several electrons as possible in t₂g although they must be paired. As displayed in diagram 3. the high- and low-spin configurations for d⁵ are (t₂g)³(e_g)² (five unpaired electrons) and (t₂g)⁵ (one unpaired electron), correspondingly.

The spin state of a transition metal ion can frequently measure by the paramagnetic susceptibility. For ions of the 3d series it is found that very complexes with ligands like halides, water or ammonia are high-spin compounds, the noteworthy exception being Co³⁺, a d⁶ ion that generally creates low spin compounds. Low-spin complexes are found with strong field ligands like CN^-, and almost always with 4d and 5d elements anything the ligand.