Catalytic behavior of hexaphenyldisiloxane in the synthesis of pyrite FeS

Functional small molecules afford opportunities to direct solid-state inorganic reactions at low temperatures. Here, we use catalytic amounts of organosilicon molecules to influence the metathesis reaction: FeCl 2 + Na 2 S 2 → 2NaCl + FeS 2 . Specifically, hexaphenyldisiloxane ((C 6 H 5 ) 6 Si 2 O) is shown to increase pyrite yields in metathesis reactions performed at 150 °C. In situ synchrotron X-ray diffraction (SXRD) paired with differential scanning calorimetry (DSC) reveals that diffusion-limited intermediates are circumvented in the presence of (C 6 H 5 ) 6 Si 2 O. Control reactions suggest that the observed change in the reaction pathway is imparted by the Si-O functional group. 1 H NMR supports catalytic behavior, as (C 6 H 5 ) 6 Si 2 O is unchanged ex post facto . Taken together, we hypothesize that the polar Si-O functional group coordinates to iron chloride species when NaCl and Na 2 S 4 form, forming an unidentified, transient intermediate. Further exploration of targeted small molecules in these metathesis reaction provides new strategies in controlling inorganic materials synthesis at low-temperatures. Hexaphenyldisiloxane acts catalytically to yield FeS 2 in metathesis reactions at low temperatures (150 °C) compared to reactions with no molecule.