Uranyl Analogue Complexes—Current Progress and Synthetic Challenges

Uranyl ions, {UO2}n+ (n = 1, 2), display trans, strongly covalent, and chemically robust U-O multiple bonds, where 6d, 5f, 6p orbitals play important roles. The synthesis of isoelectronic analogues uranyl has been interest for quite some time, mainly with the purpose unveiling covalence 5f-orbital participation in bonding. Significant advances have occurred last two decades, initially marked by uranium(VI) bis(imido) complexes, first a {RNUNR}2+ core, later followed unique trans-{EUO}2+ (E S, Se) recently highlighted complexes featuring linear {NUN} moiety. This review covers synthesis, structure, bonding, reactivity uranium containing {EUE}n+ core 0, to {OUO}n+ incorporating ?- ?-donating ligands that can engage uranium–ligand oxygen may be replaced heavier chalcogenido, imido, nitride, carbene ligands, or transition metal. It focuses on synthetic methods well-defined molecular species condensed phase but also references gas-phase low-temperature-matrix experiments, as well computational studies lead valuable insights.