Cubic co-ordination: crystal structure of sodium octafluoroprotactinate(V)

Abstract

The structure of sodium octafluoroprotactinate(V), Na,PaFs. has been determined by X-ray diffraction methods and refined by full-matrix least-squares techniques. The crystals are of tetragonal symmetry,;in space group I4/mmrn (D4,,I7) with a = 5.493 and c = 10.970 8 ; Z = 2, Each protactinium atom is bonded to eight fluorine atoms which lie at the corners of an almost perfect cube. The Pa-F bond distance is 2.21 8. The sodium atoms are located between the PaFa3-cubes. Metal-fluorine and fluorine-fluorine distances have been calculated for the isostructural uranium and neptunium compounds, Na,U Fs and Na,NpF8, respectively.RESULTS obtained from X-ray powder photographs and reported1s2 for N%PaF, and Na,UF, suggest that the co-ordination around the central-metal atom should be an example of the hitherto unknown cubic arrangement. The crystal structure of Na,PaF, has, therefore, been examined by single-crystal X-ray methods in order to test this deduction EXPERIMENTAL

Double photoexcitation involving2pand4felectrons inL3-edge x-ray absor

“…The participation of 5f orbitals of Pa͑V͒ to the bonding with fluorine has been found necessary to explain the structure of Na 3 PaF 8 , wherein the Pa atom lies in the center of an almost perfect cube. 20 In aqueous solution, the two oxidation states Pa͑IV͒ and Pa͑V͒ have been established. Pa͑V͒ is stable under oxic conditions in solutions.…”

Crystal and molecular structures of the octakis(pyridine N-oxide) lanthanide complexes M(PyO)8(ClO4)3, M = lanthanum and neodymium

“…While the preceding discussion deals with the polyhedron in La(PyO)83+ as lying along the reaction path interconnecting the square antiprism and the cube, it is pertinent to examine the dihedral angles (6) between the shape-determining edges, as defined by Muetterties and Guggenberger,21 to assess the Of form IX + mY + nZd = 0 where X, Y, and Z are coordinates referred to orthogonal axes with X and Y parallel to the crystallographicx and y axes. 6 In A X 103. Numbers in the left column are the plane numbers.…”

“…Only equivalent B is reported for the general perchlorate group. For La: Bu = 2.47 (6), B22 = 1.70 (6),B33 = 2.32 (7), and B13 = 0.38 (5) where the form of the thermal ellipsoid is exp[-(2¡EyA¡Ay/-¡*ry*B¡y)/4], with i, ¡ = 1,2, 3. c These atoms refined as a rigid group constrained to lie on the twofold axis: center of gravity 0.0, 0.2260 (16), 0.25. d Group temperature factor. b Refined anisotropically: 5,, = 3.41 (8), 5 22 = 3.04 ( 8), 5 33 = 2.24 (8),5 12 = 0.00 (8), B13 = -0.62 (5), and B23 = 0.03 (7).where the form of a Group temperature factors: 11.59 (38), 11.13 (37), 14.56 (75), and 16.55 (81), respectively.…”

Relation between angular parameters in prismatic and antiprismatic complexes

“…The metal atom at the origin of the cartesian frame is sandwiched between two equilateral triangles of equivalent ligand atoms L1L2L3 and Li'L2,L3/ parallel to the xy plane. The M-L bonds each make the same angle 9 with the z axis. The M-Li bond lies in the xz plane, and 8 is the angle between the x axis and the projection of M-Li' on the xy plane.…”