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Rational Design of Sequestering Agents for Plutonium and Other Actinides

N-silylated benzamidines: versatile building blocks in main group and coordination chemistry

Publisher Summary This chapter discusses the X-ray structural analyses of organolithium compounds. Lithium compounds, perhaps the most widely used organometallic synthetic intermediates, have fascinating structures. Nevertheless, organic chemistry textbooks often treat organolithium compounds merely as “carbanions” or as monomers. The chemical behavior of lithium compounds cannot be understood without the knowledge of the structures, the degree of aggregation, and the extent and nature of solvation. “Terminally bonded” organolithium compounds afford, in principle, the simplest examples of lithium–carbon σ–bonds. This class comprises lithium compounds with a single contact between lithium and a carbon atom. The dimer of lithiobicyclo butane, and of lithiodimethylsulfide, illustrates the bridging between sp 3 -hybridized carbon atoms while phenyllithium exemplifies bridging between sp 2 carbon atoms. A few organolithium compounds crystallize in aggregates with more than four subunits. Such compounds, derived from substituted acetylenic substrates (excluding simple acetylides), form oligomeric structures involving bridging lithium atoms and possible interactions of the lithium atoms with acetylenic π system. The benzophenonedilithium compound 50, formed by the reduction of benzophenone with lithium metal, crystallizes as a dimer. A large number of mixed-metal organometallic compounds have been prepared in which the hydrocarbon ligands bridge the lithium and the other metal atoms. A number of lithium/transition-metal compounds involving metal–metal multiple bonds as well as lithium–alkyl group interactions have been structurally characterized. The structure of lithium compounds without lithium–carbon bonds summarizes the structures of some lithium compounds that do not involve Li–C contacts.

X-ray structural analyses of organolithium compounds

Synthesis, Structure, and Reactions of Hydride, Borohydride, and Aluminohydride Compounds of the f-Elements.

Gold η2-Coordination to Unsaturated and Aromatic Hydrocarbons: The Key Step in Gold-Catalyzed Organic Transformations

Structure and dynamics in metal tetrahydroborates. II. Vibrational spectra and structures of some transition metal and actinide tetrahydroborates

The composition of the compound (C/sub 5/H/sub 5/)/sub 2/UCl/sub 2/, prepared from uranium tetrachloride and thallium cyclopentadienide in DME (1,2-dimethyoxyethane), has been investigated in the solid state by infrared spectroscopy and x-ray powder diffraction, and in solution by electronic and /sup 1/H NMR spectroscopy. All results indicate that (C/sub 5/H/sub 5/)/sub 2/UCl/sub 2/ is a mixture of the known compounds (C/sub 5/H/sub 5/)/sub 3/UCl and (C/sub 5/H/sub 5/)UCl/sub 3/(DME). The structure of this latter species is proposed to be mer pseudooctahedral on the basis of solution NMR studies (which also show it to be sterochemically dynamic) and by analogy to the related complex, (CH/sub 3/C/sub 5/H/sub 4/)UCL/sub 3/(THF)/sub 2/, the solid-state molecular structure of which has been determined using single-crystal x-ray diffraction techniques. This compound crystallizes in the monoclinic space group P2/sub 1//n with four molecules in a cell of dimensions a = 10.481 (2) A, b = 12.981 (2) A, c = 13.834 (2) A, and ..beta.. = 105.86 (1)/sup 0/. Least-squares refinement of the 181 variables led to a value for the conventional R index (on F) of 0.058 for 3698 independent reflections having 2 theta/sub MoK..cap alpha..-bar/ 3 sigma(I). The coordinationmore » geometry about the uranium ion is approximately mer octahedral with the eta/sup 5/-CH/sub 3/C/sub 5/H/sub 4/ and one coordinated THF occupying trans axial positions, and the other THF and three chlorine atoms occupying equatorial positions. The U--C (cyclopentadienyl), U--Cl, and U--O distances average 2.720 (14), 2.623 (3), and 2.450 (8) A, respectively. The principal distortion of the coordination geometry from octahedral is a 0.47-A displacement of the uranium atom out of the equatorial plane toward the cyclopentadienyl ring. It is found that the THF ligands of (C/sub 5/H/sub 5/)UCl/sub 3/(THF)/sub 2/ are readily displaced by nitrogenous bases such as 2,2'-bipyridyl and 1,10-phenanthroline. 6 figures, 6 tables.« less

The Nature of Bis(cyclopentadienyl)uranium Dichloride and Cyclopentadienyluranium Trichloride in Solution and in the Solid State

Bis(η5-cyclopentadienyl)vanadium Tetrahydroborate. A Covalent Organotransition Metal Borohydride with Unusual Spectroscopic and Dynamic Properties

A method was reported for synthesizing a series of highly stable biscyclopentadienyluranium(IV) halide systems. For the chloride compounds, anionic biscyclopentadienides containing a variable bridging group were reacted with uranium tetrachloride in tetrahydrofuran (-78/sup 0/). Mass spectral, NMR and ir methods were used to study the molecular structure and chemical properties with special emphasis on Li U/sub 2/Cl/sub 5/(CH/sub 2/(C/sub 5/H/sub 4/)/sub 2/)/sub 2/(OC/sub 4/H/sub 8/)/sub 2/. (DDA)

William J. Kennelly

Papers

Structure and dynamics in metal tetrahydroborates. II. Vibrational spectra and structures of some transition metal and actinide tetrahydroborates

The Nature of Bis(cyclopentadienyl)uranium Dichloride and Cyclopentadienyluranium Trichloride in Solution and in the Solid State

Bis(η5-cyclopentadienyl)vanadium Tetrahydroborate. A Covalent Organotransition Metal Borohydride with Unusual Spectroscopic and Dynamic Properties

Ring-bridged bis(cyclopentadienyl)uranium(IV)halides

Hexafluoro-2-butyne-metal atom chemistry. Stable complexes, small organometallic clusters, and metal-acetylene telomers