Expanding the Nonaqueous Chemistry of Neptunium: Synthesis and Structural Characterization of [Np(NR2)3Cl], [Np(NR2)3Cl]-, and [Np{N(R)(SiMe2CH2)}2(NR2)]- (R = SiMe3).

Abstract

Reaction of 3 equiv of NaNR2 (R = SiMe3) with NpCl4(DME)2 in THF afforded the Np(IV) silylamide complex, [Np(NR2)3Cl] (1), in good yield. Reaction of 1 with 1.5 equiv of KC8 in THF, in the presence of 1 equiv of dibenzo-18-crown-6, resulted in formation of [{K(DB-18-C-6)(THF)}3(μ3-Cl)][Np(NR2)3Cl]2 (4), also in good yield. Complex 4 represents the first structurally characterized Np(III) amide. Finally, reaction of NpCl4(DME)2 with 5 equiv of NaNR2 and 1 equiv of dibenzo-18-crown-6 afforded the Np(IV) bis(metallacycle), [{Na(DB-18-C-6)(Et2O)0.62(κ1-DME)0.38}2(μ-DME)][Np{N(R)(SiMe2CH2)}2(NR2)]2 (8), in moderate yield. Complex 8 was characterized by 1H NMR spectroscopy and X-ray crystallography and represents a rare example of a structurally characterized neptunium-hydrocarbyl complex. To support these studies, we also synthesized the uranium analogues of 4 and 8, namely, [K(2,2,2-cryptand)][U(NR2)3Cl] (2), [K(DB-18-C-6)(THF)2][U(NR2)3Cl] (3), [Na(DME)3][U{N(R)(SiMe2CH2)}2(NR2)] (6), and [{Na(DB-18-C-6)(Et2O)0.5(κ1-DME)0.5}2(μ-DME)][U{N(R)(SiMe2CH2)}2(NR2)]2 (7). Complexes 2, 3, 6, and 7 were characterized by a number of techniques, including NMR spectroscopy and X-ray crystallography.