Uranium(IV)-crown-ether complexes and cryptates. 1H Nuclear magnetic resonance study, and X-ray crystal and molecular structure of tetrachloro-(2,5,8,15,18,21-hexaoxatricyclo[20.4.0.09,14]hexacosane)uranium(IV)

Abstract

Uranium( IV) -Crown-etherComplexes and Cryptates. 'H Nuclear Magnetic Resonance Study, and X-Ray Crystal and Molecular Structure of Tetrachloro -(2,5,8,15,18,2 1hexaoxatr icyclo [20.4.8 .09i14] hexacosane)uranium( IV)

(18-Crown-6)-μ-oxo-hexakis(tetrahydroborato)diuranium(IV): an unprecedented asymmetric dinuclear complex

“…Atom U1 is located at the centre of the 18-crown-6 molecule, in which it is held by six bonds to the ether O atoms. The UÐO(ether) bond lengths are in the range 2.517 (6)± 2.581 (6) A Ê and their average value of 2.55 (2) A Ê is in good agreement with the values of 2.55 (9) (de Villardi et al, 1978) and 2.53 (5) A Ê (Bombieri et al, 1978) in similar systems. The six ether O atoms de®ne a mean plane with an r.m.s.…”

“…Examples of hexa-coordinated (18-crown-6)uranium complexes are uncommon. The ®rst to be reported were uranium(IV) complexes, in which the coordination sphere was completed by three chloride groups (de Villardi et al, 1978;Bombieri et al, 1978). A bis(tetrahydroborate) uranium(III) complex with dicyclohexyl-18-crown-6 has also been described (Dejean et al, 1987), as well as several uranyl complexes (Thue  ry et al, 1995, and references therein).…”

Diphosphinoamido complexes of thorium(IV) and uranium-(IV) and -(V). Crystal structures of [{ThCl2[N(CH2CH2PPri 2)2]2}2] and [{UCl2[N(CH2CH2PEt2)2]2}2]

“…in [uc16]2-U-CI 2.625(5) A (average)}. 26 The U U distance is indicative of no metal-metal interaction. It is interesting that in 5 there is a lengthening of the U-P bond trans to amide as compared with the U-P bond trans to chloride {U(l)-P(1) [trans N(2)] 3.115(1), U(l)-P(4) [trans to N(l)] 3.154(1), U( l)-P(3) [trans to Cl(l)] 3.104(1), U(2)-P(5) [trans to N(4)] 3.095( l), U(2)-P (6) [trans to N(3)] 3.1 80( l), U(2)-P (7) [trans to C1(2)] 3.088(1) A}.…”

Structure of a tetranuclear uranium(IV) compound: hemiaquatetrakis(trifluoroacetato)uranium(IV)–4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (4/2)

“…The 1H NMR spectra of complexes of U w salts with crown ethers and cryptands in solvents with high electric constants have given evidence for direct coordination of the U atoms to the O atoms of the macrocyclic ligands; in the solid state, a structural determination has confirmed the U TM insertioia as the UC13 + cation in dicyclohexyl-18-crown-6 (de Villardi, Charpin, Costes, Folcher, Plurien, Rigny & de Rango, 1978). Attempts to isolate such complexes 0108-2701/90/101778-04503.00 with cryptands have led to crystals which could not be handled.…”