Catalytic behavior of hexaphenyldisiloxane in the synthesis of pyrite FeS2

Abstract

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: FeCl₂ + Na₂S₂ → 2NaCl + FeS₂. Specifically, hexaphenyldisiloxane ((C₆H₅)₆Si₂O) 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 (C₆H₅)₆Si₂O. Control reactions suggest that the observed change in the reaction pathway is imparted by the Si–O functional group. ¹H NMR supports catalytic behavior, as (C₆H₅)₆Si₂O is unchanged ex post facto. Taken together, we hypothesize that the polar Si–O functional group coordinates to iron chloride species when NaCl and Na₂S₄ 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.