SYNTHESIS OF NEUTRAL AND ANIONIC URANYL ARYLOXIDE COMPLEXES FROM URANYL AMIDE PRECURSORS - X-RAY CRYSTAL-STRUCTURES OF UO2(O-2,6-I-PR2C6H3)(2)(PY)(3) AND [NA(THF)(3)](2)[UO2(O-2,6-ME(2)C(6)H(3))(4)]

Reaction of anhydrous UO2Cl2 With 2 equiv of KN(SiMe(3))2 in THF leads to formation of the neutral bis(amido) complex UO2[N(SiMe(3))(2)](2)(THF)(2) (1), whereas the use of 2, 3, or 4 equiv of NaN(SiMe(3))(2) in an analogous reaction produces the tetrakis(amido) salt [Na(THF)(2)](2){UO2[N(SiMe(3))(2)](4)} (2) Alcoholysis of 1 with 2 equiv of HO-2,6-i-Pr2C6H3 in the presence of pyridine gives the bis(aryloxide) complex UO2(O-2,6-i-Pr2C6H3)2(PY)3 (3) (PY C5H5N), whereas alcoholysis of 2 with 4 equiv of HO-2,6-Me(2)C(6)H(3) in THF produces the tetrakis(aryloxide) salt [Na(THF)(3)](2)[UO2(O-2,6-Me(2)C(6)H(3))(4)] (4) The molecular structures of 3 and 4 have been determined by means of single-crystal X-ray diffraction studies. Compound 3 exhibits pentagonal bipyramidal geometry, with the uranyl oxygen atoms occupying the axial positions and the aryloxide and pyridine ligands lying in the equatorial plane. U-O bond lengths average 1.789(5) Angstrom for the uranyl oxygen atoms and 2.197(9) Angstrom for the aryloxide ligands, while U-N distances to the pyridine ligands average 2.616(7) Angstrom. Compound 4 is comprised of a uranium metal center coordinated in a pseudo-octahedral fashion by six oxygen atoms, with two sodium cations each coordinated to one uranyl oxygen atom and one oxygen atom of an aryloxide ligand. U-O bond distances to the uranyl oxygens average 1.814(5) Angstrom, while distances to the aryloxide ligands average 2,204(8) Angstrom for the two aryloxide ligands not involved in coordination to the sodium cations and 2.288(5) Angstrom for the aryloxide ligands forming U-O-Na interactions. Crystal data for 3 (at -70 degrees C): Monoclinic, space group P2(1), a = 11.582(2) Angstrom, b = 13.975(3) Angstrom, c = 12.322(2) Angstrom, beta = 103.67(3)degrees, V = 1937.9(6) Angstrom(3), Z = 2, D-calc =1.477 g cm(-3). Crystal data for 4 (at -70 degrees C): Triclinic, space group P ($) over bar 1, alpha = 12.830(2),Angstrom, b = 13.574(2) Angstrom, c = 18.382(3)Angstrom, alpha = 93.401(1)degrees, beta = 98.12(1)degrees, gamma = 106.21(1)degrees, V= 3027(2) Angstrom(3), Z= 2, D-calc = 1.35 g cm-3.