Compound 1

View in PubChem | 13C1H COSY | 1H NOESY | Vis-nIR | MDL Molfile | ChemDraw

Compound data: CIF

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

Method A, from Np^IV: a 10-mL teflon-tap equipped glass ampoule was charged with ²³⁷NpCl₄ (46.0 mg, 0.121 mmol) and K₂(L^Ar) (95.9 mg, 0.182 mmol). THF (3 mL) was condensed onto the solids at -78 °C and the resulting reaction mixture allowed to warm to 20 °C with stirring, over a 90 minute period. During this time the red-ochre solid was consumed and the colour of the solution changed to maroon and then to intense red (see Figure S 6). An off-white precipitate formed above -45 °C, increasing in quantity during the course of the reaction. The resulting suspension was allowed to stir for a further 16 h at room temperature and the red supernatant was isolated by syringe filtration (PTFE membrane, 0.45μm porosity). Slow vapour diffusion of n-pentane into this solution yielded [(L^Ar)NpCl], 1, in the form of dark red crystals and a pale yellow powder, which was characterized as organic by-products based on γ-ray spectroscopy (<0.1 mg ²³⁷Np radioassay). Attempts to purify the crude product via fractional crystallization were unsuccessful but mechanical separation of the fine yellowish powder, facilitated by repeated re-suspension of solids in pentane, allowed the isolation of 1 as a coarse red precipitate; isolated yield: ~40 mg, 46 %. Experiments to identify D₂L formation in reactions carried out in THF-d₈, which would be anticipated if a ligand-centred radical species was formed and abstracting H(D) atoms from solvent, were not conclusive.

Method B, from Np^III: A suspension of [²³⁷NpCl₃(THF)_x] is first prepared in situ: A 25-mL Schlenk tube was charged with ²³⁷NpCl₄ (175.4 mg, 0.463 mmol), solid sodium mercury amalgam (222 mg, 5.03 %, 1.05 eqv.) and mercury metal (2.013 g). THF (8 mL) was added and the reaction mixture was stirred vigorously for 4 h. A greenish-grey suspension formed immediately, and was isolated from the mercury drop by syringe (27 G hypodermic needle). To this suspension was added solid K₂(L^Ar) (243.9 mg, 0.463 mmol) at room temperature, leading to an immediate colour change of the reaction mixture to intense red. The reaction mixture was allowed to stir for further 5 h, diluted with 10 mL of THF and the supernatant isolated by filtration (fritted glass disk, 10-16 μm porosity). The filter cake was washed with THF (2 × 4 mL) and the combined filtrates were evaporated to dryness under reduced pressure. The crude red product was solubilized in the minimum amount of THF (ca. 8‑8.5 mL) and syringe-filtered (PTFE membrane, 0.45μm porosity). Slow vapour diffusion of n-pentane into the resulting solution afforded [(L^Ar)NpCl], 1, as red crystals, suitable for single crystal X-ray diffraction analysis. The crystals were collected, washed with n-pentane (4 × 1 mL) and dried under vacuum (20 °C, <5×10^-3 mbar, 6 h); isolated yield: 281 mg, 84 %. The ¹H and ¹³C NMR spectra of benzene solutions of 1 were fully assigned by correlated proton-proton and proton-carbon spectroscopy, and an nOe experiment, and are labelled according to the numbering scheme in Figure S 2. ¹H NMR (THF-d₈, 400.34 MHz): δ 7.08 (s, 4H, C2/C3 pyrrolide CH), 4.96 (s, 2H, C9 C₆H₄), 4.26 (br s, 2H, C12 C₆H₄), 3.20 (s, 12H, C7/C16 CH₃), 0.15 (s, 12H, C6/C15 CH₃), -0.39 (br s, 4H, C11/C13 meta-C₆H₄) ppm. ¹³C NMR: δ 128.6 (C2/C3), 141.2 (C9), 91.1 (C12), 36.6 (C7/C16), 28.7 (C6/C15), -104.6 (C11/C13) ppm. See below for further NMR spectral studies of 1. ATR-IR: ν = 3094 w, 3075 w, 2969 w/m, 2960 w, 2948 w, 2927 w, 2862 w, 1646 w, 1619 w, 1600 w, 1589 w, 1576 w, 1476 w/m, 1462 w/m, 1439 w, 1410 w/m, 1386 w, 1379 w, 1363 w/m, 1359 w/m, 1342 w, 1304 w, 1280 w, 1256 w/m, 1217 w/m, 1211 w/m, 1183 w, 1153 w, 1133 w/m, 1111 w, 1082 w, 1044 s, 1007 w, 985 w/m, 960 w, 935 w, 925 w, 902 w, 823 m, 809 w, 795 w, 748 s, 722 w/m, 715 m, 709 s, 677 w, 670 w, 644 w, 620 w/m, 677 w, 670 w, 645 w, 620 m, 580 m, 537 w/m, 511 w/m, 499 m, 459 w/m, 439 w/m, 429 w/m, 423 w/m, 410 m, 400 w/m, 386 w/m cm^-1. Vis-nIR (THF, 293 K): λ_max / nm (ε_max / dm³ mol^-1 cm^-1) = 1351 (28.3), 1331 (48.9), 1318 (41.9), 1280 (36.6), 1253 (27.9), 1028 (49.0), 985 (73.0), 949 (48.9), 943 (47.3), 855 (86.6), 838 (93.8), 783 (76.2), 772 (69.4), 764 (66.4), 748 (63.5), 725 (58.0), 661 (83.5), 633 (104). Radiological regulations prohibit combustion-based analysis of the C, H and N content of 1.