Gabriele Lugli

Synthesis and structure of a π-arene complex of uranium(III) - aluminum chloride

Abstract The synthesis of a π-arene uranium(III) complex with aluminium chloride obtained from UCl 4 , AlCl 3 and Al in benzene, is reported. The isolated big black crystals are thermally stable up to 100°C and are immediately decomposed by moisture. The crystal and molecular structure of the complex is reported as determined by single crystal X-ray method.

Synthesis of new alkyl and aryl σ-bonded uranium(IV) derivatives

Abstract The synthesis of some alkyl and aryl uranium (IV) derivatives of type U(π-C5H5)3R is reported. They are obtained from Cp3UCl and Li-R (R = CH3 n-C4H9, C6H5 CH2−C6H5) or RMgBr (R = CH2−pC6H4−CH3) in tetrahydrofuran. Their NMR and infrared spectra, as well as their chemical hydrolyses are in agreement with σ-bonded alkyl or aryl groups. Thermal stability in the solid state is remarkably high for all compounds.

A contribution to the organometallic chemistry of uranium: tetra(allyl)uranium

Abstract The synthesis of tetra-allyl Uranium obtained from UCl4 and C3H5 Mg Br, is reported. The isolated crystalline dark-red complex is not thermally stable above −20°C and burns spontaneously in the air. Its infrared spectra could be reasonably in agreement with π-bonded allylic groups. Thermal decomposition and cleavage with H2O gave the expected hydrocarbon products.

The synthesis and nuclear magnetic resonance investigation of the structure and chemical dynamics of new anionic tetra-allyl complexes of lanthanide ions

Abstract The synthesis and spectroscopic characterization of LiLn(allyl) 4 dioxane (Ln = Ce, Nd, Sm, Gd, Dy) from LnCl 3 and Sn(allyl) 4 are described. The dynamic behaviour of LiSm(allyl) 4 at high and low temperatures was studied and activation parameters were determined. An unusually pronounced broadening of line-width was observed at low temperature for LINd(allyl) 4 and LiCe(allyl) 4 complexes.

Mechanical and Electrical Properties of Highly Oriented Ribbons of Polyacetylene

Abstract Films of polyacetylene have been prepared which can be converted into highly oriented ribbons (HOPA) with high tensile strength (up to 150 MPa). Iodine-doped HOPA shows an electrical conductivity one order of magnitude higher than that of unstretched films.

Nuclear magnetic resonance pseudo-contact shifts in U(allyl)4

Abstract 1H-magnetic resonance of Uranium (IV)-tatra-allyl gives evidence of its being a π-allyl complex. The large chemical shifts observed are significantly affected by a pseudo-contact mechanism.

X-Ray Investigation on Highly Oriented Polyacetylene

Abstract The crystal structure of polyacetylene has been investigated by X-ray analysis on highly oriented polymers at various cis-trans content. A mosaic-like cis-trans mixed crystal model is proposed which fits the experimental X-ray data.

Paramagnetic shifts in the proton magnetic resonance spectrum of tetra(allyl)uranium(IV) and tetra(2-methylallyl)uranium(IV).

Abstract Data on the paramagnetic shifts of proton magnetic resonance signals of tetra(allyl)uranium(IV) and tetra(2-methylallyl)uranium(IV) are presented. The temperature dependence of the shifts is discussed in terms of the Kurland-McGarvey theory of the contact and pseudo-contact interactions. On the basis of the comparison between the methylated and the parent compounds a separation of the two contributions is proposed.

IMPROVED PREPARATION OF ANHYDROUS LANTHANIDE CHLORIDES UNDER MILD CONDITIONS

Abstract Oxides or carbonates of lanthanides (Ln) are converted under mild conditions into the corresponding solvated anhydrous chlorides LnCl 3 (ether) n by hydrogen chloride produced in situ from thionyl chloride and water in the presence of 1,l2-dimethoxyethane under mild conditions.

Synthesis and characterization of new mixed allyl–alkoxo-complexes of uranium(IV). The crystal and molecular structure of di-µ-isopropoxo-bis[di(η-allyl)isopropoxouranium(IV)]

New complexes of general formula [U(η-C3H5)2(OR)2][R = Et(1), Pri(2), or But(3)] have been prepared by reaction of [U(η-C3H5)4] with ROH. The crystal structure of (2) has been determined from single-crystal X-ray diffraction data (Mo-Kα radiation). The complex crystallizes in the space group P21/c with unit-cell dimensions a= 12.324(7), b= 8.535(1), c= 17.897(9)A, β= 126.71(3)°, Z= 4, and R 0.030 for 1 408 independent observations. In the dimeric molecular structure, with crystallographic site symmetry, two uranium atoms are joined by two alkoxide bridges. The co-ordination polyhedron of the uranium can be regarded as a distorted pentagonal bipyramid, whose equatorial plane is defined by the terminal carbons of the η-allyl ligands and by a bridging oxygen. The axial positions of the bipyramid are occupied by the remaining bridging oxygen and by a terminal oxygen. The latter shows a linear co-ordination [U–O–C 178.0(10)°]. Other relevant bond distances are: U–O(bridging) 2.271(10) and 2.413(10); U–O(terminal) 2.056(13); and U–C(mean) 2.679(14)A. Infrared data for (1)–(3) suggest that the uranium–allyl π bond is predominantly ionic; this is consistent with some structural peculiarities of the allyl ligands in (2). Hydrogen-1 n.m.r. results indicate monomeric structures in tetra-hydrofuran [(1)–(3)] and dimeric ones in toluene solution for (1) and (2).