Structural and Theoretical\nAssessment of Covalency\nin a Pu(III) Borohydride Complex

Despite the discovery of actinide boro­hydride complexes\nover\n80 years ago, no plutonium boro­hydride complexes have been structurally\nvalidated using single-crystal X-ray diffraction (XRD). Here we describe\nPu<sub>2</sub>(H<sub>3</sub>BP<sup><i>t</i></sup>Bu<sub>2</sub>BH<sub>3</sub>)<sub>6</sub>, the first example of a Pu(III)\nboro­hydride complex authenticated by XRD and NMR spectroscopy.\nTheoretical calculations (DFT, EDA, and QTAIM) and experimental comparisons\nof metal–boron distances suggest that metal–borohydride\ncovalency in M<sub>2</sub>(H<sub>3</sub>BP<sup><i>t</i></sup>Bu<sub>2</sub>BH<sub>3</sub>)<sub>6</sub> complexes generally decreases\nin the order M = U(III) > Pu(III) > Ln(III).