The title compound, di-mu-chloro-bis [(eta(5)-trimethylsilylcyclopentadienyl)samarium(III)], [SmCl2(C8H13Si)(4)], which has been characterized by single-crystal X-ray diffraction, is isostructural with its ytterbium analogue. The geometrical parameters of the lanthanide atoms are compared in the two compounds. Results and conclusions reported for [Yb(eta(5)-C5H4SiMe3)(2)(mu-Cl)](2) are entirely corroborated by the present structure analysis.

The availability of single crystals of neptunium tetrachloride allowed as to carry out a complete structural X-ray investigation of this compound in order to establish precise cell parameters, atomic coordinates and bond distances. NpCl4 crystallizes in tetragonal space group I41/amd (D4h19, No141) with cell dimensions a=8.229(2), c=7.437(1) Å, V=503.62(14) Å3. There are four molecules in the unit cell. The neptunium atom, with point group symmetry −42m (D4h), is surrounded by eight chlorine atoms; four chlorines are at 2.618(2) Å, and four at 2.867(2) Å from the neptunium atom. The coordination polyhedron may be described as a distorted dodecahedron; the smallest ClCl approach in the polyhedron is 3.110(3) Å. The positional parameters are in agreement with those reported for UCl4 and ThCl4. The two sets of NpCl distances, 2.618(2) Å and 2.867(2) Å, compare favourably with the values 2.650(3) Å and 2.882(3) Å in UCl4 and with the values 2.718(8) Å and 2.903(7) Å in ThCl4. They would indicate, as observed for UCl4 in a polarized neutron experiment, a tendency of NpCl bonds towards covalency.

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The title complex was prepared by reaction of YbCl3 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.

Fluorescence and excitation spectra of ${\mathrm{U}}^{3+}$:${\mathrm{LaCl}}_{3}$ are presented for pressures up to 8 GPa and shifts of 27 energy levels are derived. Corresponding changes in the Slater parameter ${\mathit{F}}^{\mathit{k}}$, the spin-orbit coupling parameter \ensuremath{\zeta}, and the crystal-parameters ${\mathit{B}}_{\mathit{q}}^{\mathit{k}}$ are evaluated. The observed variations of the free-ion parameters ${\mathit{F}}^{\mathit{K}}$ and \ensuremath{\zeta} are nearly an order of magnitude larger than in a former study on ${\mathrm{Nd}}^{3+}$:${\mathrm{LaCl}}_{3}$. The behavior of the free-ion parameters is discussed in terms of different models. The crystal-field parameters are evaluated within the superposition model yielding intrinsic parameters B${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathit{k}}$(R) (k=4,6). It is found that the distance dependence of the intrinsic parameters for ${\mathrm{U}}^{3+}$:${\mathrm{LaCl}}_{3}$ is nearly the same as in the case of ${\mathrm{Nd}}^{3+}$:${\mathrm{LaCl}}_{3}$. Calculations using the angular-overlap model describe successfully the high-presure results and indicate that the contact contributions to the crystal-field strength are the dominant terms.

The absolute uraniumligand bond disruption enthalpies for the series of compounds U(Cp′)3SEt, U(Cp★)3SX (X  Et or tBu) and U(Ind★)3SEt [Cp′ C5H4tBu, Cp★  C5H4SiMe3 and Ind★  C9H6SiMe3] 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★, tBu) and 158 ± 8 (Ind ★, Et).

Actinide-oxygen bond disruption enthalpies D(AnO) in Cp∗3AnR and Cp∗∗3AnR (Cp∗3 C5H4Si(CH3)3; Cp∗∗C5H4tBu; RH or CH3; 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∗3UH, 319 ± 10 for Cp∗3UCH3 and 392 ± 11 and 371 ± 24 for the respective Cp∗3ThR analogues. D(Cp∗∗3UO) is found at 307 ± 9 kJ mol−1. The influence of the nature of the titrants is observed in the series EtOH, CF3CH2OH, tBuOH.

Twelve new ternary intermetallic compounds of light actinide elements from Th to Pu, namely U4Tc7Si6, U4Tc7Ge6, Np4Ru7Ge6, U2Tc3Si5, Np2Re3Si5, Pu2Re3Si5, Th2Mo3Si4, U2Mo3Si4, U2Mo3Ge4, Np2Mo3Si4, Np2Mo3Ge4, and Pu2Mo3Si4, were obtained. The structures of these compounds are discussed as well as some preliminary physical property studies. Magnetic susceptibility measurements show that An2Mo3(Si or Ge)4 compounds are paramagnetic at all temperatures studied and that U4Tc7Si6 orders antiferromagnetically around 25 K. Mössbauer spectroscopy on Np4Ru7Ge6 does not show a magnetic splitting down to 4.2 K.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The bond disruption enthalpies [D(Th-X)] have been determined in the complexes Ind3*Th-X and Cp3*Th-H with Ind*  (CH3)3SiC9H6, Cp*  (CH3)3SiC5H4 and X  H or D. The thermodynamic data were obtained by iodinolysis batch-titration calorimetry. The calculated D(Ind3*Th-H), D(Ind3*Th-D) and D(Cp3*Th-H) values in toluene are, respectively, 264 ± 8 kJ mol−1, 276 ± 5 kJ mol−1 and 274 ± 6 kJ mol−1.

The asymmetric unit contains two mononuclear molecules. The coordination around each Th atom is a slightly distorted tetrahedron with three pi-bonded indenyl rings and one sigma-bonded methyl ligand. Th-C(indenyl) distances range from 2.69 (2) to 3.04 (2) angstrom and indicate a trihapto mode of bonding of the indenyl rings (through the outer, non-bridging C atoms) as previously observed in other tris(indenyl) complexes of thorium and uranium. The Th-C bonds to ethyl-substituted indenyl C atoms [2.83 (2)-2.94 (3) angstrom] are longer than the other Th-C(non-bridging) bonds [2.69 (2)-2.78 (2) angstrom]. Th-C(methyl) distances average 2.49 (3) angstrom. In one molecule each CH2-CH3 bond is approximately normal to the plane of the indenyl ring to which it is attached, while in the other molecule only two of the ethylindenyl ligands adopt this conformation; in the third ligand, the ethyl group lies in the plane of the indenyl ring. The crystal is stabilized by van der Waals interactions.

The absolute uranium-ligand bond-disruption enthalpies (kJ mol-1) of the series [U(C5H4R)3X] (X = H or I, R = Bu(t) or SiMe3) have been measured by iodinolysis batch-titration solution calorimetry in toluene: R = Bu(t), 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).

[U(C15H19)3Cl], M(r) = 871.44, triclinic, P1BAR, a = 10.081 (4), b = 13.339 (4), c = 15.083 (3) angstrom, alpha = 85.24 (4), beta = 82.673 (5), gamma = 67.37 (4)-degrees, V 1856 (1) angstrom3 Z = 2. D(x) = 1.560 g cm-3 lambda(Mo K-alpha) 0.71073 angstrom, mu = 42.491 cm-1, F(000) = 872, T = 295 (1) K, R = 0.027 for 4364 reflections [I > 3-sigma(I)]. The coordination polyhedron of the U atom is a regular tetrahedron. Geometrical molecular features indicate a tendency for a monohapto mode of bonding of the hexamethylindenyl ligands. This type of bonding has never before been observed in sigma-indenyl complexes of uranium or thorium.

The UTHF (THF = tetrahydrofuran) bond disruption in tris(indenyl)uranium tetrahydrofuranate has been obtained by iodinolysis batch-titration solution calorimetry. The D[(C9H7)3UTHF] value in toluene solution is (71.3±5.2) kJ mol−1.

[Th(C 11 H 11 ) 3 Cl] cristallise dans P2 1/c avec a=7,651, b=11,750, c=30,23 A, β=94,18 o , Z=4; affinement jusqu'a R=0,055. La coordination autour du thorium consiste en un tetraedre legerement deforme, dans lequel Th est lie a trois cycles indenyl trihapto et a un chlore 6. Les substituants ethyl semblent s'orienter preferentiellement dans le plan des cycles indenyl, sauf dans le cas d'un obstacle du a l'empilement. Deux orientations sont possibles pour les derniers carbone des ethyl, qui sont a 102 o l'une par rapport a l'autre

Uranium-ligand bond disruption enthalpies have been obtained by application of iodinolysis batch-titration solution calorimetry to the (C9H7)3U/(C9H7)3U-I/(C9H7)3U-CH3 system. Derived values in toluene solution are as follows: (C9H7)3U-I, 266.8 ± 3.2 kJ mol−1; (C9H7)3U-CH3, 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).

Treatment of triindenylthorium chloride with metallic potassium in boiling benzene has given tetraindenylthorium. No thorium(III) species was detected.

AbstractIndenylsodium (I) reacts with the thorium borohydride (II) to give diindenylthorium bis(borohydride) (III) and triindenylthorium borohydride (IV) which are separated by sublimation of (III) at 130°C/10‐3 torr.