Actinide structural studies. 13. Three pyridine–acetylacetonate complexes of actinyl(VI) ions

Abstract

Bis(1,3-diphenyl-l,3-propanedionato)oxo-(pyridine)uranium(VI) (1), [UO2(CasHllO2)2(CsHsN)], Mr= 795.6, monoclinic, P2Jn, a= 10.158 (2), b= 21.937 (8), c= 13.888 (4)A, t= 103.49 (1) ° , U = 3009 (2)/k 3, Z = 4, D x = 1.76 g cm -3, 2(Mo Ka) = 0.71069 A, /t = 51.48 cm -1, F(000) = 1536, T= 289 K, R = 0.036 for 3269 unique observed reflections. Bis[ 1-(tert-butoxy)-1,3-butanedionato]dioxo-(pyridine)uranium(IV) (2), [UO2(CaHI303)2(CsHsN)], M r= 663.5, orthorhombic, Cmc2~, a = 15.939 (9), b = 19.532 (8), c= 9.777 (6) A, U= 3044 (1) A 3, Z = 4, D x = 1.45 gcm -a, 2(Mo Kct) = 0.71069/~, /t = 50.81 cm -1, F(000) = 1280, T= 289 K, R = 0.048 for 1178 unique observed reflections. Dioxobis(2,4-pentanedionato)(pyridine)neptunium(VI) (3), [NpO2(CsH 7-O2)2(CsHsN)], Mr=546.4, orthorhombic, Fdd2, a = 29.617 (5), b= 11.406 (2), c= 10.595 (4)A, U= 3579 (2) A 3, Z=8, D x=2.03gcm -3, 2(MoKa)= Acta Cryst. Abstract.

Relationship between 237Np Mössbauer parameters and bond distances in nitrogen coordinated [NpO2(acac)2py]

“…As listed in Table II, the U-O(1) bond distance of 1.77(1) Å that we obtained now is reasonable. The O-U-O linearity is similar to the O-Np-O in I, although [3] noted that the O-U-O for the large deviation from linearity of the O-U-O bond angle, 173.5(8)-. In this study, the 237 Np-Mö ssbauer data has required our re-determination of [UO 2 (acac) 2 py].…”

“…3(2)-model [6] while fixing values of ) = 0 and H eff = 220 T using an BIGOR'' (Wave Metrics, Lake Oswego, Oregon) software. The spectrum at 40 K was fitted by fixing the values of the % and e 2 qQ because the absorption peaks were very small and broadened.…”

“…When discussing the structures of Np compounds, the 0.01 Å shorter difference has been used. However, the single crystal data for [UO 2 (acac) 2 [3]. Good agreement in the correlation between the % value and the Np-O bond distance has indicated that the reported analogous [UO 2 (acac) 2 py] structure may have some inaccuracies.…”

“…The neptunium(VI) ion in I is coordinated by six oxygen atoms and the one nitrogen atom of pyridine. The % value of I indicated that the bond distance Np-O reported in [3] is very reasonable since the correlation between the % value and the Np-O bond distance is high. It is well known that the mean Np-O bond distance of the neptunium compounds is shorter by 0.01 Å than that of analogous uranium compounds.…”

“…We now report 237 Np-Mö ssbauer spectra for [NpO 2 (acac) 2 py] I. I determined by a single crystal X-ray determination [3] exhibits a pentagonal-bipyramidal geometry about the Np(VI) ion. The neptunium(VI) ion in I is coordinated by six oxygen atoms and the one nitrogen atom of pyridine.…”