So I'm looking at the spectrochemical series of ligands which has that
I- < Br- < Cl- < F- < OH- < ox2- < H20 < NH3 < en <bpy< phen <CN-
Where the left side are weak field ligands and the right side are strong field ligands.
A lot of my homework problems involve me looking at an octahedral complex and deciding whether the complex is low or high spin and then figuring out if the complex is diamagnetic or not.
From problems I have been doing and google searches, I have found that H20 is a weak field ligand and NH3 is strong field.
I can't understand why [NiF6]2- is diamagnetic. F- should be a weak field ligand, which would mean it would lead to a high spin complex. The Ni should have an oxidation state of +4 making it d6, and in a high spin octahedral d6 complex it will not be diamagnetic. It can only be diamagnetic if it was low spin. But why is it low spin if F- is a weak field ligand????