# What prevents inner-sphere electron transfer from oxalato-iron(II) to chloro-platinum(II)?

In this book (p. 237), when talking about the reduction of $$\ce{[PtCl4]^{2-}}$$ by $$[\ce{(C2O4)2Fe]^{2-}}$$, the author states that

There is no easy route for imparting electrons onto the $$\ce{PtCl4}^{2-}$$ ion, but it may proceed more readily via the aqua-complexes $$\ce{(H2O)PtCl3-}$$

and

The pathway for the electron transfer from iron(II) to platinum(II) has not been elucidated, but in view of the labile nature of iron complexes with respect to ligand substitution it is unlikely to proceed via an 'inner sphere' mechanism, whereby the two coordination shells share a common bridging ligand.

What prevents the inner-sphere mechanism in this case?

In Taube's original example, the metal with the bridging ligand is low-spin before, and the other metal, which takes the bridging ligand, is low-spin after. Can inner-sphere transfer only occur in those kinds of cases? Here, both the Fe(III) and Fe(II) are high-spin.