Influence of alkali metal cations on the formation of the heterobimetallic actinide tert-butoxides [AnM₃(O^tBu)₇] and [AnM₂(O^tBu)₆] (An^IV = Th, U; M^I = Li, Na, K, Rb, Cs)

Abstract

Heterobimetallic tert-butoxides of alkali metal cations with actinide (IV) centers exhibit two distinctive structural motifs, [AnM2(OtBu)6] and [AnM3(OtBu)7] (AnIV = Th, U and MI = Li-Cs), evidently governed by the size of the alkali metal ions.

Mononuclear Uranium and Heterobimetallic Actinide (An=Th, U) Alkoxides with Divalent Group 14 Elements (MII=Ge, Sn, Pb)

“…The different ionic radius also affects the U−N bonds of 4 compared to 3 ( 4 : 2.66 Å, 3 : 2.57 Å). Moreover, the terminal U−O bond length observed in compound 4 closely align the bond length found in other U IV alkoxides (2.11‐2.18 Å) [6,10–11] …”

“…The recorded spectrum contains several signals in the range of −2.05 to 6.00 ppm that cannot be assigned to the [U(O t Bu) 4 (py) 2 ] ( 4 ) structure (Supporting Information, Figure S10). NMR investigations of U IV containing alkoxide derivatives, such as [ULi 2 (O t Bu) 6 (THF) 2 ], [10] [ULi 3 (O t Bu) 7 ] [11] or [UM 2 (O t Bu) 6 ] (M I =Na, K, Rb, Cs), [11] have been reported to show complex behavior.…”

“…Moreover, the terminal UÀ O bond length observed in compound 4 closely align the bond length found in other U IV alkoxides (2.11-2.18 Å). [6,[10][11] The 1 H NMR spectrum of [U(O t Bu) 4 (py) 2 ] (4) in pyridine-d 5 revealed a high complexity due to the paramagnetism of U IV . The recorded spectrum contains several signals in the range of À 2.05 to 6.00 ppm that cannot be assigned to the [U-(O t Bu) 4 (py) 2 ] ( 4) structure (Supporting Information, Figure S10).…”

“…[9] In addition to a recent report on monovalent lithium containing heterobimetallic U IV/V compounds, [10] we have systematically explored the influence of the alkali metal cation sizes on the formation of the tertbutoxides of tetravalent actinide namely [AnM 2 (O t Bu) 6 ] and [AnM 3 (O t Bu) 7 ] (An IV = Th, U; M I = LiÀ Cs). [11] Moreover, we previously reported on simple synthetic routes for the formation of heterobimetallic uranyl(VI) alkoxides of lanthanides [12] and expanded the alkoxide chemistry to Np IV . [13] The chelating tri-alkoxo metallate unit, [M(O t Bu) 3 ] À , based on divalent group 14 elements (M = Ge II , Sn II , Pb II ) exhibits a ψ1pseudo-tetrahedral coordination environment and is a versatile anion that can coordinate to a wide range of metal cations from throughout the periodic table to form heterobimetallic species (see Scheme 1).…”

“…identified the mixed‐metal Zr IV ‐U III alkoxide, [Zr 2 (O i Pr) 9 U(C 8 H 8 )], as the only alkoxide derivative containing uranium in the trivalent oxidation state [9] . In addition to a recent report on monovalent lithium containing heterobimetallic U IV/V compounds, [10] we have systematically explored the influence of the alkali metal cation sizes on the formation of the tert ‐butoxides of tetravalent actinide namely [AnM 2 (O t Bu) 6 ] and [AnM 3 (O t Bu) 7 ] (An IV =Th, U; M I =Li−Cs) [11] . Moreover, we previously reported on simple synthetic routes for the formation of heterobimetallic uranyl(VI) alkoxides of lanthanides [12] and expanded the alkoxide chemistry to Np IV [13] …”