Can someone explain why this is? In [Fe(en)3][picrate]2 this means it is FeII. So using valence bond theory they should be sp3d2 hybrid orbs. Crystal field theory is not an option in this problem, which would have made more sense to me. So in [Fe(1,10-phenanthroline)3][ClO4]2 it is also FeII but it must be in the low spin state meaning that all the e- are paired in the remaining 3d orbs not used for the hybrid bonds. While in the [Fe(en)3][picrate]2 it must be using the 4d orbs and leaving the 3d orbs alone to have the 6e- spread out over the five. Both ligand types are bidentate and both bond by the nitro. This explains the difference in magnetic moment, but why in the hell does one go high spin and the other go low?

the latter goes low because it's an ionic compound

Are you saying that [Fe(en)3][picrate]2 is covalent? It seems that both are ionic to me. How else would Fe form coordination complexes? Or are you saying that Fe(en)3 is somehow covalent? That makes no sense at all.

Why can't you use the spectrochemical series?

I finally found one that listed phen. Both have N bidentates. I still have a little trouble understanding why, when they are so close in the series, phen is low spin and en is high. It doesn't matter I have more than the answer I need, I was just curious. Thanks. Now on to crystal field