“…The scientific understanding of the role that f-electrons play in the bonding, electronic structure, − redox chemistry, − and physics of the actinides (An) is continually evolving. ,, Widespread advances over the last 30 years have remapped the known boundaries of molecular Th and, in particular, U molecular chemistry. Progress has ranged from the discovery of new oxidation states (An 2+ ; An = Th, U, Np, Pu) ,− ,, to an array of non-actinyl multiple-bond chemistry, − ,− to covalency studies ,,,− and small molecule reactivity. ,, An expanding and diverse synthetic “toolbox” of nonaqueous, organic solvent soluble Th/U starting materials has been key in facilitating the explosion of molecular chemistry studies for these early actinide elements. Addressing the documented limitation of U 3+ starting materials, in the late 1980s and mid-1990s, facile routes were reported to [UI 3 (THF) 4 ] (THF = tetrahydrofuran), [UI 3 (DME) 2 ] (DME = 1,2-dimethoxyethane), [UI 3 (py) 4 ] (py = pyridine), and [UBr 3 (THF) 4 ], through oxidation of amalgamated uranium metal turnings with I 2 or Br 2 in Lewis base solvents. , This route to [UI 3 (THF) 4 ] (and other Lewis base adducts) as well as the synthesis of [U(N″) 3 ] (N″ = {N(SiMe 3 ) 2 }) generated from these halide complexes (which was more convenient than prior routes to [U(N″) 3 ], which comprised the in situ reduction of UCl 4 with Na/(C 10 H 8 ) and then reaction with NaN″), has become a staple of U chemistry. , Building upon those contributions, additional precursors and routes to U 3+ and U 4+ synthons have been established using U 0 metal as the source material and also metallic-phase-free routes.…”