Structural and Theoretical Assessment of Covalency in a Pu(III) Borohydride Complex

Despite the discovery of actinide borohydride complexes over 80 years ago, no plutonium borohydride complexes have been structurally validated using single-crystal X-ray diffraction (XRD). Here we describe Pu₂(H₃BPBu₂BH₃)₆, the first example of a Pu(III) borohydride complex authenticated by XRD and NMR spectroscopy. Theoretical calculations (DFT, EDA, and QTAIM) and experimental comparisons of metal-boron distances suggest that metal-borohydride covalency in M₂(H₃BPBu₂BH₃)₆ complexes generally decreases in the order M = U(III) > Pu(III) > Ln(III).