The first uranium bis­(acyl)­phosphide (BAP) complexes were synthesized from the reaction between sodium bis­(mesitoyl)­phosphide (Na­( mes BAP)) or sodium bis­(2,4,6-triisopropylbenzoyl)­phosphide (Na­( tripp BAP)) and UI3(1,4-dioxane)1.5. Thermally stable, homoleptic BAP complexes were characterized by single-crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopy, when appropriate, for the elucidation of the electronic structure and bonding of these complexes. EPR spectroscopy revealed that the BAP ligands on the uranium center retain a significant amount of electron density. The EPR spectrum of the trivalent U­( tripp BAP) 3 has a rhombic signal near g = 2 (g 1 = 2.03; g 2 = 2.01; and g 3 = 1.98) that is consistent with the EPR-observed unpaired electron being located in a molecular orbital that appears ligand-derived. However, upon warming the complex to room temperature, no resonance was observed, indicating the presence of uranium character.

This perspective provides an introduction to magnetic circular dichroism (MCD) spectroscopy and its efficacy in elucidating both fundamental electronic structure and in situ reaction speciation in d- and f-block organometallics.

As prevalent cofactors in living organisms, iron−sulfur clusters participate in not only the electron-transfer processes but also the biosynthesis of other cofactors. Many synthetic iron−sulfur clusters have been used in model studies, aiming to mimic their biological functions and to gain mechanistic insight into the related biological systems. The smallest [2Fe−2S] clusters are typically used for one-electron processes because of their limited capacity. Our group is interested in functionalizing small iron−sulfur clusters with redox-active ligands to enhance their electron storage capacity, because such functionalized clusters can potentially mediate multielectron chemical transformations. Herein we report the synthesis, structural characterization, and catalytic activity of a diferric [2Fe− 2S] cluster functionalized with two o-phenylenediamide ligands. The electrochemical and chemical reductions of such a cluster revealed rich redox chemistry. The functionalized diferric cluster can store up to four electrons reversibly, where the first two reduction events are ligand-based and the remainder metal-based. The diferric [2Fe−2S] cluster displays catalytic activity toward silylation of dinitrogen, affording up to 88 equiv of the amine product per iron center.

Experimental and computational studies support an inner-sphere radical pathway for iron-catalysed C–H activation/functionalisation with allyl electrophiles.