Intermolecular Interactions of CpFePPh3(CO)CO(CH2)5CH3: From a Crystalline Solid to a Supramolecular “Iron-Truss” Polymer

PPh3CpFe­(CO)­(CO)­(CH2)5CH3 (FpC6) spontaneously forms supramolecular polymers in the solid state. The polymers crystallize slowly over a period of one month and can be recovered by melting the crystals at 65 °C. The rheological profile of FpC6 fits the Maxwell model indicating the presence of chain entanglement. Crystal analysis reveals that FpC6 is able to assemble, via cooperative π–π interactions and weak C–H···O hydrogen bonding, into a duplex chain structure with truss arrangement of iron atoms. Powder X-ray diffraction (PXRD) of the polymers shows a double-peak pattern, characteristic for duplex ladder polymers. FTIR/ATR analysis further supports that carbonyl groups are involved in C–H···O hydrogen bonding responsible for the self-assembly. This discovery opens up new design motifs for organometallic supramolecular polymers.