Do "weak-field" and "high spin" complexes refer to the same thing?
The spectrochemical series only gives info on the relative strength of the ligand field. Whether or not a metal complex is high or low spin (assuming there is an appropriate number of d electrons that both are possible) is a function of both the ligand and the metal center.
Thus, it is possible for &quot;weak field&quot; ligand to be in a low spin complex if the metal center favors low spin. For example, almost all complexes of second and third series transition metals are low spin, independent of ligand identities.