# How do I know which transition metal complex is most stable?

Jul 29, 2017

$\text{How do you compare apples and oranges.......?}$
You know that that when a transition metal ion is in octahedral coordination, the ligand field strongly differentiates between axial and non-axial $\text{d-orbitals}$. For octahedral coordination, this occurs for ${d}^{4} , {d}^{5} ,$ ${d}^{6}$, and ${d}^{7}$ metal ions, which can generate low spin (differentiation between ${t}_{\text{2g}}$ and ${e}_{g}$ is large), and high spin (differentiation between ${t}_{\text{2g}}$ and ${e}_{g}$ is small) complexes.
Half-filled d-orbitals, ${d}^{5}$, and fully-filled d-orbital configurations, ${d}^{10}$, tend to have a special stability, but for each scenario it is hard to find a metric with which to make meaningful comparison.