= Solution
The six diphosphines bind the six Pd centres, occupying two adjacent sites on each and displacing two pyridines per Pd. Reassembly therefore favours the two-connected Pd nodes of the bipyramid instead of the cube's four-connected nodes. The balanced transformation is
$$
\boxed{[\mathrm{Fe}_8\mathrm{Pd}_6L_8]^{28+}+6\,\mathrm{dppp}\longrightarrow2[\mathrm{Fe}_2\mathrm{Pd}_3L_2(\mathrm{dppp})_3]^{10+}+4[\mathrm{Fe}L]^{2+}}.
$$
Thus \b[two cages of type 4 and four free <metalloligands> of type 3] form per cage 5. <iron>, <palladium>, ligand and charge balances all close. Strong phosphine <chelation> drives the donor replacement, while the release of additional discrete species can favour entropy. The analogous conversion is observed experimentally in the cited heterobimetallic system.<Dynamic Complex-to-Complex Transformations of Heterobimetallic Systems Influence the Cage Structure or Spin State of Iron(II) Ions by Matthias Hardy and others>[Scheme 3 and discussion of six-equivalent dppp addition]{ref}
Back to article page
