Enantiopure Ferrocenophanes with Phosphorus in Bridging Positions: Thermostability and Ring-Opening Polymerization

The thermal stability of four related, enantiopure phospha[1]ferrocenophanes 2R, equipped with different R groups (R = Ph, iPr, CH2SiMe3, tBu) at the bridging phosphorus atom, was investigated by differential scanning calorimetry. The chirality of 2R stems from the planar chirality of the ferrocene moiety (Sp,Sp)-2,2′-diisopropylferrocenediyl. Within this group of [1]ferrocenophanes ([1]FCPs) the Ph-substituted species 2Ph resulted in the largest heat release [ΔH = −86(±2) kJ mol–1] and, therefore, was subjected to preparative thermal ring-opening polymerization (ROP). ROP of 2Ph gave a polymer fraction (44%), which was analyzed by gel permeation chromatography in its sulfurized form (Mw = 19 kDa; D = 1.3). The remaining fraction of the reaction mixture was composed of cyclic oligomers that were sulfurized to facilitate their characterization. Mass spectrometric analysis revealed the presence of cyclic oligomers (n = 2–6), with the dominating dimer signal. Chromatographic separation (preparative thin-lay...