J. Goffart

The first cationic indenyl-f-metal complexes with pentagonal bipyramidal geometry. Crystal structures of [C9H7UBr2(CH3CN)4]+2 [UBr6]2− and [{C9H7UBr(CH3CN)4}2O]2+ [UBr62−☆

Abstract Treatment of the octahedral complexes, C9H7AnHal3·2C4H8O (An = U r Th) with verypure methyl cyanide leads to the formation of the novel complexes [C9H7AnHal2(CH3CN)4]+2 [AnHal62− (I). Reaction of C9H7UHal3·2C4H8O with methyl cyanide containing dry oxygen gives the red complex [{C9H7UHal-(CH3CN)4}2O]2+ [UHal6]2− (II). Both uranium complexes with Hal = Br have been characterized by elemental analysis, vibration spectroscopy and X-ray structure analysis. The cation in I exhibits a pentagonal bipyramidal geometry and that in II consists of two pentagonal bipyrmids bonded by an oxygen occupying the common apex. A series of analogous compounds containing the 1-ethylindenyl, 1, 4, 7-trimethylindenyl or 1,2,3,4,5,6,7-heptamethylindenyl anion has been prepared and characterized . The reactions of the octahedral compounds with butyronitirle and benzonitrile is discussed.

Organo-f-element thermochemistry. Thorium-ligand bond disruption enthalpies in {(CH3)3SiC9H6}3ThX (X H or D) and in {(CH3)3SiC5H4}3ThH complexes

Abstract The bond disruption enthalpies [D(Th-X)] have been determined in the complexes Ind 3 *Th-X and Cp 3 *Th-H with Ind*  (CH 3 ) 3 SiC 9 H 6 , Cp*  (CH 3 ) 3 SiC 5 H 4 and X  H or D. The thermodynamic data were obtained by iodinolysis batch-titration calorimetry. The calculated D(Ind 3 *Th-H), D(Ind 3 *Th-D) and D(Cp 3 *Th-H) values in toluene are, respectively, 264 ± 8 kJ mol −1 , 276 ± 5 kJ mol −1 and 274 ± 6 kJ mol −1 .

New actinide ternary intermetallic compounds: synthesis, characterization and physical properties

Abstract Twelve new ternary intermetallic compounds of light actinide elements from Th to Pu, namely U 4 Tc 7 Si 6 , U 4 Tc 7 Ge 6 , Np 4 Ru 7 Ge 6 , U 2 Tc 3 Si 5 , Np 2 Re 3 Si 5 , Pu 2 Re 3 Si 5 , Th 2 Mo 3 Si 4 , U 2 Mo 3 Si 4 , U 2 Mo 3 Ge 4 , Np 2 Mo 3 Si 4 , Np 2 Mo 3 Ge 4 , and Pu 2 Mo 3 Si 4 , were obtained. The structures of these compounds are discussed as well as some preliminary physical property studies. Magnetic susceptibility measurements show that An 2 Mo 3 (Si or Ge) 4 compounds are paramagnetic at all temperatures studied and that U 4 Tc 7 Si 6 orders antiferromagnetically around 25 K. Mossbauer spectroscopy on Np 4 Ru 7 Ge 6 does not show a magnetic splitting down to 4.2 K.

Organo-f-element thermochemistry. Absolute uraniumligand bond disruption enthalpies of [UL3SX] complexes (L C5H4tBu, C5H4SiMe3 or C9H6SiMe3 and X Et or tBu)

Abstract The absolute uraniumligand bond disruption enthalpies for the series of compounds U(Cp′) 3 SEt, U(Cp★) 3 SX (X  Et or t Bu) and U(Ind★) 3 SEt [Cp′ C 5 H 4 t Bu, Cp★  C 5 H 4 SiMe 3 and Ind★  C 9 H 6 SiMe 3 ] have been measured by an oxidative addition process involving batch-titration solution calorimetry in toluene. The derived values are as follows (kJ mol −1 ): 252 ± 8 (Cp′, Et); 266 ± 9 (Cp★, Et); 158 ± 8 (Cp★, t Bu) and 158 ± 8 (Ind ★, Et).

Organo-f-element thermochemistry. Uranium-ligand bond disruption enthalpies in the (C9H7)3U/(C9H7)3U-I/(C9H7)3U-CH3 system

Abstract Uranium-ligand bond disruption enthalpies have been obtained by application of iodinolysis batch-titration solution calorimetry to the (C 9 H 7 ) 3 U/(C 9 H 7 ) 3 U-I/(C 9 H 7 ) 3 U-CH 3 system. Derived values in toluene solution are as follows: (C 9 H 7 ) 3 U-I, 266.8 ± 3.2 kJ mol −1 ; (C 9 H 7 ) 3 U-CH 3 , 196.3 ± 6.6 kJ mol −1 . The correlation between the latter value and that obtained recently by alcoholysis confirms that the value of D (U-I) is certainly a better parameter for placing D data on an absolute scale than D (U-O).

Absolute uranium–ligand bond-disruption enthalpies of [U(C5H4R)3X] complexes (X = I or H, R = But or SiMe3)

The absolute uranium–ligand bond-disruption enthalpies (kJ mol–1) of the series [U(C5H4R)3X](X = H or I, R = But or SiMe3) have been measured by iodinolysis batch-titration solution calorimetry in toluene: R = But, 246.3 ± 5.3 (X = I), 249.7 ± 5.7 (X = H); R = SiMe3, 265.6 ± 4.3 (X = I), 251.7 ± 5.1 (X = H).

Organo-f-element thermochemistry. Actinide-ligand bond disruption enthalpies in tris(indenyl)actinide hydrocarbyls

Abstract Thorium- and uranium-ligand bond disruption enthalpies ( D (AnR)) have been obtained for the series of complexes Ind 3 AnR, where Ind  C 9 H 7 or 1-C 2 H 5 C 9 H 6 , An  Th or U, R = an alkyl group. All the new compounds have been characterised by microanalysis and spectroscopy. The thermodynamic data were determined by oxygen-free batch-titration, solution calorimetry from the enthalpies of solution of the organo- f -element complexes in toluene and from the subsequent enthalpies of alcoholysis with 2,2,2-trifluoroethanol. D (An) gas values obtained (95% of confidence) were as follows: (C 9 H 7 ) 3 ThCH 2 Si(CH 3 ) 3 , (397 ± 7) kJ mol −1 ; (C 9 H 7 ) 3 ThCH 3 , (371 ± 6) kJ mol −1 ; (1-C 2 H 5 C 9 H 6 ) 3 ThCH 3 , (365 ± 5) kJ mol −1 ; (C 9 H 7 ) 3 ThCH(CH 3 ) 2 , (357 ± 8) kJ mol −1 ; (C 9 H 7 ) 3 UCH 3 , (351 ± 2) kJ mol −1 ; (1-C 2 H 5 C 9 H 6 ) 3 UCH 3 , (350 ± 4) kJ mol −1 and (C 9 H 7 ) 3 ThCH 2 C 6 H 5 , (342 ± 9) kJ mol −1 . These bond disruption enthalpies parallel, but are significantly larger than, those for the identical R functionalities in the (C 5 H 5 ) 3 ThR series. For corresponding Th/U pairs, the difference { D (ThR) − D (UR)} is ca. 20 kJ mol −1 .

Alkylindenyl organoactinides: synthetic chemistry, characterization and physical properties

Abstract Tris(1-ethylindenyl)actinide chloride and tris(1,4,7-trimethylindenyl)-actinide chloride (An = U and Th) have been prepared and characterized by chemical analysis and mass spectrometry. The electronic, infrared, Raman and NMR spectra have been recorded. No major steric hindrance was detected and the alkylindenyl groups appear mainly as pentahapto bonded to the actinide. The spectroscopic measurements are consistent with the single crystal X-ray structure of tris(1,4,7-trimethylindenyl)uranium chloride. The magnetic susceptibility of the uranium compounds has been measured between 2 and 300 K.

Dicyclopentadienyl complexes of ytterbium(III). The crystal structure of [Yb(η5-C5H4SiMe3)2(μ-Cl)]2

Abstract The title complex was prepared by reaction of YbCl 3 with Li (C 5 H 4 SiMe 3 ) in tetrahydrofuran. A single crystal X-ray diffraction study has revealed that the complex is dimeric with bridging chlorine atoms. A flattened tetrahedron around each ytterbium atom is formed by the centroids of two cyclopentadienyl rings and the two bridging chlorine atoms. Comparison of bond distances and angles with those reported for similar dicyclopentadienylytterbium complexes shows that substitution on the cyclopentadienyl ligands by bulky trimethylsilyl groups does not affect the stereochemistry about the lanthanide atom.

Organo-f-element thermochemistry

Abstract Actinide-oxygen bond disruption enthalpies D (AnO) in Cp ∗ 3 AnR and Cp ∗∗ 3 AnR (Cp ∗ 3  C 5 H 4 Si(CH 3 ) 3 ; Cp ∗∗ C 5 H 4 t Bu; RH or CH 3 ; AnU or Th) have been measured by iodinolysis and alcoholysis titration calorimetry. D (AnO) values are as follows (kJ mol −1 : 317 ± 15 for Cp ∗ 3 UH, 319 ± 10 for Cp ∗ 3 UCH 3 and 392 ± 11 and 371 ± 24 for the respective Cp ∗ 3 ThR analogues. D( Cp ∗∗ 3 UO ) is found at 307 ± 9 kJ mol −1 . The influence of the nature of the titrants is observed in the series EtOH, CF 3 CH 2 OH, t BuOH.