Martine Nierlich

Bis(crown ether) and Azobenzocrown Derivatives of Calix[4]arene. A Review of Structural Information from Crystallographic and Modelling Studies

The association within one molecule ofcalix[4]arene and crown ether moieties leads toligands with new complexing properties. In particular,calix[4]arene bis(crown-6) and some of itsderivatives have been shown to be highly selectiveextractants for caesium ions. This review presents thebackground of the study and the results of crystalstructure determinations and molecular modellingcalculations performed during the investigation of twomolecular families, the bis(crown ether) and theazobenzocrown derivatives of calix[4]arene.

The affinity and selectivity of terdentate nitrogen ligands towards trivalent lanthanide and uranium ions viewed from the crystal structures of the 1 ∶ 3 complexes

Treatment of LnI3 (Ln = La, Ce) or [UI3(py)4] with 3 equivalents of terpy in acetonitrile gave the tris(terpy) complexes [M(terpy)3]I3. Addition of 3 equivalents of Rbtp (2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine) to MX3 (X = I or OSO2CF3) in pyridine or acetonitrile afforded the tris(Rbtp) compounds [M(Rbtp)3]X3. By comparison with terpy, the Rbtp ligand has a better affinity for the 4f and 5f ions and is more selective for U(III) than for Ce(III) or La(III). This trend has been revealed by 1H NMR competition experiments and X-ray crystallographic studies which show that in the [M(terpy)3]3+ and [M(Rbtp)3]3+ cations, the M–N(Rbtp) bond lengths are shorter than the M–N(terpy) bond lengths, and the U–N bond lengths are shorter than the corresponding Ce–N or La–N bond distances.

Synthesis and crystal structure of the oxo-bridged bimetallic organouranium complex [(Me3SiC5H4)3U]2[μ-O]

Abstract The compound (Me 3 SiC 5 H 4 ) 3 U (I) reacts with CO 2 or N 2 O to give [(Me 3 SiC 5 H 4 ) 3 U] 2 [μ-O] (II), the crystal structure of which reveals presence of a linear U-O-U bridge with U-O distances of 2.1053 (2) A.

Simple Preparations of the Anhydrous and Solvent‐Free Uranyl and Cerium(IV) Triflates UO2(OTf)2 and Ce(OTf)4 − Crystal Structures of UO2(OTf)2(py)3 and [{UO2(py)4}2(μ‐O)][OTf]2

Treatment of UO3 with pure triflic acid TfOH at 110 °C or with boiling triflic anhydride TfOTf afforded [UO2(OTf)2] (1) in high yields. The latter was also prepared by the reaction of UO3 with TfOH in water, or by dehydration of [UO2(OTf)2(H2O)n] in boiling TfOTf. Anhydrous [Ce(OTf)4] (2) was similarly obtained from the commercially hydrated compound. X-ray analysis revealed that in [UO2(OTf)2(py)3] (3), the triflate ligands are monodentate whereas they are dissociated in [{UO2(py)4}2(μ-O)][OTf]2 (4).

BISPENTAMETHYLCYCLOPENTADIENYL URANIUM(IV) THIOLATE COMPOUNDS. SYNTHESIS AND REACTIONS WITH CO2 AND CS2

Abstract The bisthiolate uranium complexes [U(Cp*)2(SR)2] (R=Me, iPr, tBu, Ph) were synthesized by treatment of [U(Cp*)2(Cl)2] with NaSR; the crystal structure of [U(Cp*)2(SMe)2] was determined. Their reactions with CO2 or CS2 gave the insertion derivatives [U(Cp*)2(SR)(E2CSR)] (E=O and R=tBu; E=S and R=Me, iPr or tBu) and [U(Cp*)2(E2CSR)2] (E=O and R=tBu; E=S and R=Me or tBu); [U(Cp*)2(StBu)(S2CStBu)] was characterized by its crystal structure. Treatment of this latter with CO2 gave the mixed insertion complex [U(Cp*)2(O2CStBu)(S2CStBu)]. Thermolysis of the insertion compounds led to the reverse elimination reaction of CO2 and CS2. Reduction of [U(Cp*)2(O2CStBu)2] with Na(Hg) afforded the corresponding U(III) anionic complex.

Selective Complexation of Uranium(III) over Cerium(III) and Neodymium(III) by 2,2′:6′,2′′-Terpyridine − X-ray Crystallographic Evidence for Uranium-to-Ligand π Back-Bonding

The addition of 2,2′:6′,2′′-terpyridine (terpy) to MI3 (M = Ce, Nd, U) in anhydrous pyridine led to the quantitative formation of the bis-terpy complexes [MI2(terpy)2]I [M = Ce (1) and Nd (2)] and [MI2(terpy)2L]I [M = U and L = pyridine (3); M = Ce and L = H2O (4)]. Conductometry measurements indicated that these complexes are 1:1 electrolytes in pyridine solution. 1H NMR competition experiments showed that the terdentate ligand has a better affinity for UIII than for CeIII or NdIII. The X-ray crystal structures of solvates of 1−4 have been determined. The average U−N(terpy) bond lengths in 3 are 0.05 A shorter than the mean Ce−N bond length in 4; the U−N(central pyridine) distances are shorter than the U−N(distal pyridines) distances in 3, while the reverse order is found in the early lanthanide compounds. These differences could reflect the presence of a π back-bonding interaction between the uranium atom and the terpy ligand. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Tetramethylphospholyluranium complexes and their pentamethylcyclopentadienyl analogues

Abstract The mono- and bis-(tetramethylphospholyl)uranium complexes [U(tmp)(Cl) 3 (L) 2 ] (tmp = C 4 Me 4 P, L = tetrahydrofuran or L 2 = dimethoxyet

Arene uranium borohydrides: synthesis and crystal structure of (η-C6Me6)U(BH4)3

Thermal decomposition of U(BH4)4 (I) in mesitylene afforded red crystals of (η-mesitylene)U(BH4)3 (II); displacement of the arene ligand of II by hexamethylbenzene gave (C6Me6)U(BH4)3 (III). The crystal structure of III revealed tetrahedral coordination, with the BH4 ligands eclipsed by three methyl substituents of the aromatic ring. The cyclopentadienyl complexes CpU(BH4)3, Cp2U(BH4)2Na, Cp3U(BH4)Na, and Cp3U(THF) were prepared from II.

Anionic triscyclopentadienyluranium(III) hydrides

Abstract Addition of H − to [(C 5 H 4 R) 3 U] (R  H, Me, SiMe 3 , or t Bu) or sodium amalgam reduction of the U IV hydrides [(C 5 H 4 R) 3 UH] (R  SiMe 3 , or t Bu) afforded the hydrido-bridged anions [(C 5 H 4 R) 3 UHU(C 5 H 4 R) 3 ] − (R  H or Me) or the monomeric anions [(C 5 H 4 R) 3 UH] − (R  SiMe 3 or t Bu). Crystals of [Na(18-crown-6)(THF) 2 ][(C 5 H 4 SiMe 3 ) 3 UHU(C 5 H 4 SiMe 3 ) 3 ] were obtained from an equimolar mixture of [Na(18-crown-6)][(C 5 H 4 SiMe 3 ) 3 UH] and [(C 5 H 4 SiMe 3 ) 3 U] and their structure determined.

Synthesis, structure and oxidative addition reactions of triscyclopentadienyluranium(III) nitrile complexes

Abstract The U III nitrile complexes [U(cp) 3 (NCR)1 (cp =η-C 5 H 5 ; R = Me, n Pr, i Pr or t Bu) have been prepared by treatment of [U(cp) 3 (THF)] (THF, tetrahydrofuran) with the corresponding nitrile; the crystal structures of [U(cp) 3 (NC n Pr)] and [U(cp) 3 (NC i Pr)] have been determined. Reaction of [U(cp) 3 (THF)] with benzonitrile at room temperature or thermolysis of the adducts [U(cp) 3 (NCR)] (R = Me or n Pr) afforded an equimolar mixture of the U IV compounds [U(cp) 3 (CN)] and [U(cp) 3 (R)] (R = Me, n Pr or Ph).