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Expanding the Nonaqueous Chemistry of Neptunium: Synthesis and Structural Characterization of [Np(NR<sub>2</sub>)<sub>3</sub>Cl], [Np(NR<sub>2</sub>)<sub>3</sub>Cl]<sup>−</sup>, and [Np{<i>N</i>(R)(SiMe<sub>2</sub><i>C</i>H<sub>2</sub>)}<sub>2</sub>(NR<sub>2</sub>)]<sup>−</sup> (R = SiMe<sub>3</sub>)

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60

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2021

Year

Selena L. Staun, Lauren M. Stevens, Danil E. Smiles, Conrad A. P. Goodwin, Brennan S. Billow, Brian L. Scott, Guang Wu, Aaron M. Tondreau, Andrew J. Gaunt, Trevor W. Hayton
Inorganic Chemistry

Abstract

Reaction of 3 equiv of NaNR<sub>2</sub> (R = SiMe<sub>3</sub>) with NpCl<sub>4</sub>(DME)<sub>2</sub> in THF afforded the Np(IV) silylamide complex, [Np(NR<sub>2</sub>)<sub>3</sub>Cl] (<b>1</b>), in good yield. Reaction of <b>1</b> with 1.5 equiv of KC<sub>8</sub> in THF, in the presence of 1 equiv of dibenzo-18-crown-6, resulted in formation of [{K(DB-18-C-6)(THF)}<sub>3</sub>(μ<sub>3</sub>-Cl)][Np(NR<sub>2</sub>)<sub>3</sub>Cl]<sub>2</sub> (<b>4</b>), also in good yield. Complex <b>4</b> represents the first structurally characterized Np(III) amide. Finally, reaction of NpCl<sub>4</sub>(DME)<sub>2</sub> with 5 equiv of NaNR<sub>2</sub> and 1 equiv of dibenzo-18-crown-6 afforded the Np(IV) bis(metallacycle), [{Na(DB-18-C-6)(Et<sub>2</sub>O)<sub>0.62</sub>(κ<sup>1</sup>-DME)<sub>0.38</sub>}<sub>2</sub>(μ-DME)][Np{<i>N</i>(R)(SiMe<sub>2</sub><i>C</i>H<sub>2</sub>)}<sub>2</sub>(NR<sub>2</sub>)]<sub>2</sub> (<b>8</b>), in moderate yield. Complex <b>8</b> was characterized by <sup>1</sup>H 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 <b>4</b> and <b>8</b>, namely, [K(2,2,2-cryptand)][U(NR<sub>2</sub>)<sub>3</sub>Cl] (<b>2</b>), [K(DB-18-C-6)(THF)<sub>2</sub>][U(NR<sub>2</sub>)<sub>3</sub>Cl] (<b>3</b>), [Na(DME)<sub>3</sub>][U{<i>N</i>(R)(SiMe<sub>2</sub><i>C</i>H<sub>2</sub>)}<sub>2</sub>(NR<sub>2</sub>)] (<b>6</b>), and [{Na(DB-18-C-6)(Et<sub>2</sub>O)<sub>0.5</sub>(κ<sup>1</sup>-DME)<sub>0.5</sub>}<sub>2</sub>(μ-DME)][U{<i>N</i>(R)(SiMe<sub>2</sub><i>C</i>H<sub>2</sub>)}<sub>2</sub>(NR<sub>2</sub>)]<sub>2</sub> (<b>7</b>). Complexes <b>2</b>, <b>3</b>, <b>6</b>, and <b>7</b> were characterized by a number of techniques, including NMR spectroscopy and X-ray crystallography.

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