Basil Kanellakopulos

Preparation and characterization of the first triscyclopentadienyl lanthanoid complexes containing two aliphatic nitrile ligands: Crystal and molecular structures of the isomorphous compounds Trans-bis(acetonitrile)tris(η5cyclopentadienyl)lanthanoid(III) (Ln = La, Ce, Pr). A successful confirmation of the solid ‘solid angle sum rule’

Abstract Systematic studies to arrive at some first examples of the sterically congested complex type Cp3Ln(NCR)2 (Cp = η5-C5H5, Ln = lanthanoid element) resulted in the preparation and detailed spectroscopic characterization of analytically pure representatives of this type with Ln = La, Ce and Pr, but not with Nd (R = CH3, and C2H5 for Ln = La only). The crystal and molecular structures of representatives of the isomorphous series Cp3Ln(NCCH3)2, (Ln = La, Ce, Pr) were determined from three-dimensional X-ray diffraction data. The compounds crystallize in the orthorhombic space group Pnca (standard group Pbcn) with: a = 14.940(3), b = 14.074(3), c = 8.596(2)A, Z = 4, R = 0.070, Rw = 0.079 for 1633 intensity data (La derivative, I); a = 14.906(3), b = 13.974(3), c = 8.502(2)A, R = 0.041, Rw = 0.047 for 1378 intensity data (Ce derivative, VII); a = 14.936(3), b = 13.986(3), c = 8.498(2)A, R = 0.031 for 1372 intensity data (Pr derivative, IX). According to the X-ray crystallographic results, the novel complexes are trigonal bipyramidally coordinated with three η5-bonded Cp rings in the equatorial plane (Ln—ring centre distances 2.62, 2.64 for La, 2.58, 2.59Afor Ce and 2.57, 2.57Afor Pr and two acetonitrile groups in the axial positions (Ln N 2.785 for La, 2.749 for Ce, 2.752 for Pr). The range of the distances in the three derivatives is in agreement with the trend in the crystal radii along the lanthanoid series. Pure 1:2 adducts involving any alkyl group larger than R = C2H5 could not be isolated. The relative stabilities of the novel Cp3Ln(NCR)2 systems, with respect to the decreasing ionic radius (i.e. from La to Nd) and to the variable space demanded by the group R, are in excellent accord with independent expectations based on the recently developed cone packing model (‘SAS-rule’) for f-element organometallics.

Metallorganische Chemie des Technetiums: VIII. Technetium(I)-carbonyl-Komplexe mit Polypyrazol-1-yl-borato-Liganden im Vergleich mit seinen Mn- und Re-Homologen

Abstract The compounds HB(C3H3N2)3Tc(CO)3 and HB(3,5-Me2C3HN2)3Tc(CO)3 have been synthesized for the first time, and their molecular and crystal structure as well as the structures of the known analogous compounds of manganese and rhenium determined by single-crystal X-ray diffraction. The IR-, 1H-NMR-, 13C-NMR-, UV- and EI-MS-spectroscopic data are discussed in correlation to the electric dipole moment and the charge distribution within the molecule.

Das erste dreiwertige thorium in einem aromatenkomplex: tris(cyclopentadienyl) thorium(III)

Zusammenfassung Durch Reduktion von Tris (cyclopentadienyl)Thorium(IV)- Chlorid mittels metallischem Natrium in Anwesenheit von Naphthalin in Tetrahydrofuran gelang es zum ersten Mal einen Aromatenkomplex mit dreiwertigem Thorium (h5-C5H5)3Th, (Tris(cyclopentadienyl)Thorium(III)), zu synthetisieren und zu isolieren. Das violettfarbene, schwach paramagnetische, kristalline (C5H5)3Th stellt eine gegenuber Luft und Feuchtigkeit auβerst empfindliche Substanz dar. Die neue Verbindung wurde spektroskopisch, magnetochemisch und rontgenographisch untersucht.

Beobachtung metallorganischer uran(IV)-fluorid-assoziate mit anomalen magnetischen und spektroskopischen eigenschaften: anzeichen für direkte uran-uran-wechsel wirkungen☆

Abstract Four complexes of the type (C 5 H 5 ) 3 U IV X (X = F, Cl, Br and I) have been subjected to systematic studies of their 1 H-NMR- and IR/VIS-spectra as a function of temperature, and these results have ben supplemented by data from FIR-, 19 F-NMR-, molecular weight- and magnetic susceptibility measurements. Unlike its homologues, the complex with X = F exhibits a surprisingly strong tendency to appear in associated forms, both in solution and in the solid rate. (C 5 H 5 ) 3 U IV F, the first organometallic actinide complex to give polynuclear species, gives e.g. in toluene solution rise to at least two non-identical equilibrium components. There is strong evidence that one of the forms, predominant below 0°, is a system with considerable spin exchange, most probably between the 5 f -electrons of neighbouring metal ions linked together by UFU-briding bonds. This particularly interesting species with direct metal-metal interaction is, however, not formed if weak Lewis-base molecules are present. In this latter case only “magnetically normal” components participat in another, strongly temperature dependent equilibrium.

Homoscorpionates (hydridotris(1-pyrazolyl)borato complexes) of the trivalent 4fions. The crystal and molecular structure of [(HB(N2C3H3)3]3LnIII, (Ln Pr, Nd) ☆

Abstract The compounds [( η 3 -HB(N 2 C 3 H 3 ) 3 ] 3 M of scandium, yttrium, lanthanum and of the trivalent lanthanides from cerium to lutetium (with the exception of promethium) have been synthesized by the reaction of MCl 3 with K[HB(N 2 C 3 H 3 ) 3 ] in tetrahydrofuran or in water. The crystal and molecular structures of the Pr and Nd compounds were determined by single-crystal X-ray diffraction. The crystal structure corresponds to the structure of the praseodymium trichloride (LaCl 3 -type). The Pr 3+ is nine-coordinate to the N atoms of the three Tp ligands. One N atom of each of the three Tp ligands and the Pr ion are almost coplanar with a PrN distance of 278.3 pm, while all other six N atoms are at a distance of 260.9 pm in a tricapped trigonal prismatic arrangement. The MN distances in the Nd compound are 280.4 (3 x) and 259.9 (6 x) pm. IR spectroscopic studies have shown that the metal ion in the LnTp 3 compounds from La to Dy is nine-coordinate, while in the compounds of the heavier lanthanides from Ho to Lu, of Sc, and Y, the central ion is eight-coordinate.

Koordinative komplexe des antibasen—basen-systems urantetrachlorid und tricyclopentadienyluran(IV)-chlorid

Abstract Novel coordination compounds of uranium tetrachloride with tricyclopentadienyluranium(IV) chloride of the compositions [(C 5 H 5 ) 3 U] 2 UCl 6 · 2DME, [(C 5 H 5 ) 3 U] 2 UCl 6 and [(C 5 H 5 ) 3 U]UCl 5 have been synthesized by the following reactions in dimethoxyethane: (a) UCl 4 + 2TlC 5 H 5 , (b) UCl 4 + U(C 5 H 5 ) 4 and (c) UCl 4 + 2(C 5 H 5 ) 3 UCl. The solvent-free compounds have been prepared in benzene in a similar manner. The physical and chemical properties of these compounds are reported.

Zur Elektronenstruktur von metallorganischen Komplexen der f-elemente

The temperature dependence of the magnetic susceptibility of Uranocene ((C8H8)2U(IV)) between 1.25 and 298 K has been measured for the first time and the results correlated with a systematic study of the crystal field splitting. Independent estimates of the three crystal field parameters B20, B40and B60were obtained by adopting the purely electrostatic approach, the angularoverlap-model and the MHW-MO-method. Subsequently the crystal field splitting pattern was calculated by a simultaneous diagonalisation of the complete f2-matrix.Assuming rigorous D8h-crystal field symmetry, a crystal field splitting pattern involving a singlet ground state and a low lying first excited doublet state (ΔE=17cm−1, ¦ΔJ2¦ = 1) gives the best agreement with both the MO-results and the experimental findings. The experimental l/χ-vs-T-curve is reproduced to a good approximation by a calculation employing the optimal parameter set: B20= −5610, B40= −1426,B60= −730cm−1.A crystal field of slightly lowered symmetry having a significantly split doublet ground state and hence positive B20-values cannot be completely ruled out.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente: XXIX. Optische und magnetochemische untersuchungen an Mono- und Bis-Acetonitriladdukten des Grundkörpers Tris(η5-cyclopentadienyl)praseodym(III)

Abstract The results of absorption, emission and magnetochemical measurements for mono and bisacetonitrile adducts derived from tris(η5-cyclopentadienyl)praseodmium(III) are reported. On the basis of these measurements the truncated crystal field splitting pattern of Cp3Pr·NCCH3 could be derived. The absorption and luminescence spectra of Cp3Pr(NCCH3)2 however, lead to two different splitting patterns. The parameters of an empirical Hamiltonian were fitted to the experimentally derived splitting patterns. In order to favour one of the two alternative parameter sets for Cp3Pr(NCCH3)2;, model calculations adopting the angular overlap model have been performed. Additionally, from the eigenvectors and eigenvalues obtained from the alternative fits, the temperature dependence of the paramagnetic susceptibility was calculated and compared with experimental data.

Oxo-bridged bimetallic organouranium complexes: The crystal structure of μ-oxo-bis[tris(cyclopentadienyl)uranium(IV)]

Abstract Oxidation of (C 5 H 5 ) 3 U III ·THF with oxygen in tetrahydrofuran yields the linear bridged complex [(C 5 H 5 ) 3 U][μ-O]. Three cyclopentadienyl rings are η 5 -covalently bonded to each uranium atom to form a distorted tetrahedron with one bridging oxygen atom. The UOU angle is 180° with the oxygen atom on a centre of inversion. The UO distance, 2.0881(4) A, is among the shortest ever observed. The temperature-dependent paramagnetic susceptibility of the compound was measured in the temperature range between 4.2 and 300 K and is discussed in comparison with the magnetic susceptibilities of (C 5 H 5 ) 3 UOH, (C 5 H 5 ) 3 USH and [(C 5 H 5 ) 3 U] 2 [μ-S].

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente ☆: LI. Synthese, Kristall-, Molekül- und Elektronenstruktur von Cp3Nd(NCCH3)2

Cp 3 Nd(NCCH 3 ) 2 ( 1 ) crystallizes in the orthorhombic space group Pbcn with a =13.961(2) A, b =8.484(2) A, c =14.840(2) A, Z =4, R =0.0359, R w =0.0408 for 1191 data and I >3 σ ( I ). Like in the case of the La, Ce and Pr derivatives the Nd 3+ central ion of compound 1 is pseudo trigonal bipyramidally coordinated by three η 5 -bonded Cp rings in the equatorial plane (Nd–ring centre distances 2.561 A, 2.554 A) and two acetonitrile groups in the axial positions (Nd–N=2.764(5) A). The absorption spectra of extremely sensitive 1 (pellets), the much more stable optically diluted Cp 3 La 0.8 Nd 0.2 (NCCH 3 ) 2 ( 2 ) (Single crystals), Cp 3 La(NCCH 3 ) 2 ( 3 ) (Single crystals) and Cp 3 Nd·NCCH 3 ( 4 ) (pellets) were recorded at room and low temperatures. From the spectra obtained, truncated crystal field splitting patterns of complexes 2 and 4 were derived, and simulated by fitting the parameters of an empirical Hamiltonian. For 56 and 55 assignments, respectively, reduced r.m.s. deviations of 32.3 cm −1 and 20.9 cm −1 are achieved for 2 and 4 . From the parameters used the experimentally based non-relativistic and relativistic molecular orbital schemes in the f range are set up for 2 and 4 . On the basis of the calculated wavefunctions and eigenvalues obtained from the fits, the spectroscopic splitting factors (extracted from the EPR spectrum) of 2 and the temperature dependence of μ eff 2 of 1 and 4 can be explained. The existence of Cp 3 La(NCCH 3 ) 2 :Tb 3+ ( 5 ) is proved by the luminescence spectrum of this complex.