Ligand K-edge Determination of Periodic Trends in Metal (Ti, Zr, Hf, Th, U) - Phosphorus Covalency

Understanding chemical trends down a full column of the periodic table is limited due to the paucity of complexes that can equivalently host both d-block and f-block metal sites. We have synthesised a series of phosphanide [M(Tren)(PH2)] (1) and phosphinidene [M(Tren)(PH)]-1 (2) organometallic compounds (M = Ti, Zr, Hf, Th, U). The two variants of compound differ in the nature of metal-phosphorous bonding – (1) containing a single M-P bond, while (2) exhibits an M=P double-bond. We propose to quantify metal-phosphorous bond covalency using phosphorous K pre-edge XANES analysis at ID21.This is a unique opportunity to study a full triad of the d-block and link it to the actinides, probing the 3d/4d/5d/6d/5f contributions to bonding. The results of this experiment will unlock differences in d-block versus f-block chemical properties, furthering the field of actinide covalency studies and providing a basis for improved nuclear waste management protocols.