A trigonal bipyramidal uranyl amido complex: Synthesis and structural characterization of [Na(THF)(2)] [UO2(N(SiMe3)(2))(3)]

Citation
Cj. Burns et al., A trigonal bipyramidal uranyl amido complex: Synthesis and structural characterization of [Na(THF)(2)] [UO2(N(SiMe3)(2))(3)], INORG CHEM, 39(24), 2000, pp. 5464-5468
Citations number
35
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
INORGANIC CHEMISTRY
ISSN journal
0020-1669 → ACNP
Volume
39
Issue
24
Year of publication
2000
Pages
5464 - 5468
Database
ISI
SICI code
0020-1669(20001127)39:24<5464:ATBUAC>2.0.ZU;2-C
Abstract
The synthesis and structural characterization of a rare example of a uranyl complex possessing three equatorial ligands, [M(THF)(2)][UO2(N(SiMe3)(2))( 3)] (3a, M = Na; 3b, M = K), are described. The sodium salt 3a is prepared by protonolysis of [Na(THF)(2)](2)[UO2(N(SiMe3)(2))(4)], wherea's the potas sium salt 3b is obtained via a metathesis reaction of uranyl chloride UO2Cl 2(THF)(2) (4) with 3 equiv of K[N(SiMe3)(2)]. A single-crystal X-ray diffra ction study of 3a revealed a trigonal-bipyramidal geometry about uranium, f ormed by two axial oxo and three equatorial amido ligands, with average U=O and U-N bond distances of 1.79675) and 2.310(4) Angstrom, respectively. On e of the oxo ligands is also coordinated to the sodium counterion. H-1 NMR spectroscopic studies indicate that THF adds reversibly as a ligand to 3 to expand the trigonal bipyramidal geometry. The degree to which the coordina tion sphere in,3 is electronically satisfied;with only three amido donors:i s suggested by (1) the reversible THF coordination, (2) a modest elongation in the bond distances for a five-coordinate U(VI) complex, and (3) the bas icity of the oxo ligands as evidenced ih the contact to Na. The vibrational spectra of the series of uranyl amido complexes [UO2(N(SiMe3)(2))(n)](2-n) (n = 2-4) are compared, to evaluate the effects on the axial U=O bonding a s a function of increased electron density donated from the equatorial regi on. Raman spectroscopic measurements of the nu (1) symmetric O=U=O stretch show progressive axial bond weakening as the number of amido donors is incr eased. Crystal data for [Na(THF)(2)][UO2(N(SiMe3)(2))(3)]: orthorhombic spa ce group Pna2(1), a = 22.945(1) Angstrom, b = 15.2830(7) Angstrom, c = 12.6 787(6) Angstrom, z = 4, R1 = 0.0309, wR2 = 0.0524.