Strong Uranium-Phosphorus Antiferromagnetic Exchange Coupling in a Crystalline Diphosphorus Radical Trianion Actinide Complex

The dominant form of elemental nitrogen on Earth is dinitrogen, but elemental phosphorus is found predominantly as white phosphorus or other singly bonded allotropes. Thus, there is interest in studying diphosphorus derivatives, most notably trapping between metal ions affording diphosphorus in +2, +1•, 0, 1-•, 2-, and 4- charge states. However, the diphosphorus radical trianion form had
previously remained elusive due to the instability of main group diatomics with large, odd negative charges. Here, we disclose a crystalline diuranium diphosphorus radical trianion complex with strong antiferromagnetic uranium-phosphorus magnetic exchange coupling parameters, up to -731 cm-1. That is over five times that of lanthanide and similar or exceeding d-block metal-metal and - ligand exchange couplings despite being based on a 5f-metal typically regarded as possessing contracted valence orbitals compared to d-block ions generally. This highlights exchange coupled f-element-p-block radical bridged character than can be engendered in molecular magnetism.