Reactivity of uranium(iv) bridged chalcogenido complexes U^IV–E–U^IV(E = S, Se) with elemental sulfur and selenium: synthesis of polychalcogenido-bridged uranium complexes

Abstract

We report the syntheses, electronic properties, and molecular structures of a series of polychalcogenidobridged dinuclear uranium species. These complexes are supported by the sterically encumbering but highly flexible, single N-anchored tris(aryloxide) chelator (Ad ArO) 3 N 3À. Reaction of an appropriate uranium precursor, either the U(III) starting material, [((Ad ArO) 3 N)U(DME)], or the dinuclear monochalcogenido-bridged uranium(IV/IV) compounds [{((Ad ArO) 3 N)U(DME)} 2 (m-E)] (E ¼ S, Se), with elemental sulfur or selenium, yields new complexes with a variety of bridging chalcogenide entities mE m nÀ (E ¼ S, m ¼ 2, n ¼ 1 or 2 and E ¼ Se, m ¼ 2, 4; n ¼ 2). Activation of the heavy chalcogens typically requires either a coordinatively unsaturated, strongly-reducing metal complex or a compound with a metalmetal bond. Since uranium complexes in the +IV oxidation state, are generally considered rather unreactive, the observed reaction of the here employed uranium(IV)/(IV) species with elemental chalcogens is fairly remarkable.

Assessing crystal field and magnetic interactions in diuranium-μ-chalcogenide triamidoamine complexes with UIV–E–UIV cores (E = S, Se, Te): implications for determining the presence or absence of actinide–actinide magnetic exchange

“… 45 The two Tren TIPS ligands in 2 adopt an eclipsed orientation when viewed along the U–S–U bond vector. The two identical U–S bond distances in 2 of 2.6903(6) Å lie at the upper end of the range of bridging U IV –S bonds in reported examples [2.588(1)–2.713(2) Å], 40 – 44 alluding to the sterically encumbered nature of Tren TIPS , but are slightly shorter than the sum of the covalent single bond radii of uranium and sulfur (2.73 Å), 46 supporting the presence of a U IV –S–U IV unit.…”

“…A crop of orange crystals was isolated from the filtrate after cooling to 5 °C, which was identified as 2 by a crystallographic unit cell check and 1 H NMR spectroscopy. The very low yield of 2 from this reaction (7%) highlights the consistently poor crystalline yields of 2 due to the inherent sensitivity and lability of U–S and E–E bonds, 44 , 54 , 55 and also the thermodynamic favourability of U–S–U formation, given that 2 is the only product of note from this reaction.…”

“… 28 – 34 These complexes have been supported by the sterically demanding ligand N(CH 2 CH 2 NSiPr i 3 ) 3 (Tren TIPS ), which also supported the synthesis of a terminal mono(oxo) complex. 35 Seeking to extend our range of chalcogenide complexes we extended our studies to heavier chalcogens, noting that from related group 15 and thorium derivatives, 28 – 34 , 36 – 39 and recent reports of diuranium-chalcogenide complexes, 14 , 40 – 44 that complexes with bridging U–E–U cores were likely to result (E = S, Se, Te). We reasoned that this would present a family of U–E–U complexes with which to systematically probe their electronic structure and magnetism.…”

Neodymium(III) Complexes Capable of Multi‐Electron Redox Chemistry

“…[20,21] Furthermore,t he unusual twist-boat metallacycle noted here for Nd is unique to the bottom of the Periodic Table;t ransition metal counterparts do not display this conformer. [20,21] Furthermore,t he unusual twist-boat metallacycle noted here for Nd is unique to the bottom of the Periodic Table;t ransition metal counterparts do not display this conformer.…”

Neodymium(III) Complexes Capable of Multi‐Electron Redox Chemistry

“…Elemental chalcogen activation has been previously noted with uranium, but generally persulfide (S 2 2− ) compounds result . Furthermore, the unusual twist‐boat metallacycle noted here for Nd is unique to the bottom of the Periodic Table; transition metal counterparts do not display this conformer.…”