Reactivity of iron(II) bis(imino)pyridine complexes with PH ₃

Bis(imino)pyridine (PDI) iron complexes have been extensively investigated as efficient catalysts in a range of transformations, notably for the polymerisation of olefins. We have expanded on the coordination chemistry of PDI-iron complexes and herein present the synthesis and characterisation of three new cationic iron(II) bis(imino)pyridine complexes (2a-c) with in situ data suggesting PH 3 is weakly bound to the iron centre. We also demonstrate the challenges associated with using PH 3 as a ligand in these systems where single crystal X-ray diffraction (sc-XRD) has revealed an array of decomposition and untargeted materials that arise during crystallisation of these unstable, reactive cationic PDI-iron complexes.