1. Advantages of Chemical Redox Agents 878 2. Disadvantages of Chemical Redox Agents 879 C. Potentials in Nonaqueous Solvents 879 D. Reversible vs Irreversible ET Reagents 879 E. Categorization of Reagent Strength 881 II. Oxidants 881 A. Inorganic 881 1. Metal and Metal Complex Oxidants 881 2. Main Group Oxidants 887 B. Organic 891 1. Radical Cations 891 2. Carbocations 893 3. Cyanocarbons and Related Electron-Rich Compounds 894

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Chemical Redox Agents for Organometallic Chemistry

Synthetic organic chemists enjoy the luxury of having a large collection of reliable reactions at their disposal for preparing small molecules, mesoscopic structures, and polymers. Coordination chemists, on the other hand, are faced with the fact that transition metal chemistry, when normalized for the number of transition metals, has relatively few high-yielding reactions, when compared to the chemistry of carbon, for preparing even small molecule structures. This lack of control is manifested, in large part, in the weak metal-ligand interactions found in coordination complexes as compared with the strong covalent bonds in organic compounds. Weak bonding often translates into many reaction pathways that are not substantially different from an energetic point of view, and therefore, results in poor selectivity. As a result, many coordination chemists in recent years have come to the realization that it may be easier and more productive to develop straightforward and reliable routes to mesoscopic supramolecular structures by capitalizing on the modest collection of high-yielding reactions in coordination chemistry, the directional bonding afforded by metal centers, and strategies aimed at taking advantage of the weak metal bonds found in coordination complexes. Three emerging synthetic strategies, the symmetry-interaction, directional-bonding, and weak-link synthetic approaches, all use metal centers as structural building blocks to rationally assemble molecular components into supramolecular metallocyclophanes. These three approaches are discussed herein, and the fundamental principles underlying each as well as their capabilities are compared and contrasted.

Strategies for the Construction of Supramolecular Compounds through Coordination Chemistry

Crown ethers: sensors for ions and molecular scaffolds for materials and biological models.

Iron-catalyzed hydroxyl radical formation. Stringent requirement for free iron coordination site.

The literature has shown numerous contributions on the synthesis and physicochemical properties of persistent organic radicals but there are a lesser number of reports about their use as building blocks for obtaining molecular magnetic materials exhibiting an additional and useful physical property or function. These materials show promise for applications in spintronics as well as bistable memory devices and sensing materials. This critical review provides an up-to-date survey to this new generation of multifunctional magnetic materials. For this, a detailed revision of the most common families of persistent organic radicals—nitroxide, triphenylmethyl, verdazyl, phenalenyl, and dithiadiazolyl—so far reported will be presented, classified into three different sections: materials with magnetic, conducting and optical properties. An additional section reporting switchable materials based on these radicals is presented (257 references).

Playing with organic radicals as building blocks for functional molecular materials

C14Fto is orthorhombic, space group Pbca, with a = 9.59 (1), b = 9.59 (1), c = 27.34 (2) A, Z = 8. The structure was refined to R = 5.25% for 1202 counter amplitudes [I > 2.5a(I)]. The molecule is essentially planar, but its long axis is slightly bent so that the aromatic rings make an in-plane angle of 4 ° with one another. The C C triple-bond length is 1.198 /~ and the two C(sp)-C(sp 2) lengths average 1.419 /~, (uncorrected for thermal libration). E.s.d.'s are 0 .0040.006 /k for bond lengths and 0-4-0.5 ° for bond

Structures of polyfluoroaromatic compounds. V. Crystal structure of perfluorodiphenylacetylene

The crystal structure of pentafluorotropolone

Crystals of the title compound are monoclinic, space group P21/c, with Z= 4 in a cell of dimensions a= 9·60, b= 15·46, c= 13·49 A(all ±0·01 A), β= 98·6°± 0·05°. The structure was determined by Fourier and least squares methods from three-dimensional X-ray counter-data and refined by least squares to R 6·4% for 1339 structure amplitudes. The piperidine ring is in the chair conformation with the ester group oriented axially. The acetylcholine-like portion adopts a conformation similar to, but somewhat more compact than, that of acetylcholine in crystals of the bromide salt.

Stereochemistry of anticholinergic agents. Part III. Crystal and molecular structure of piperidolate (N-ethyl-3-piperidyl diphenylacetate) hydrochloride

X-Ray crystallographic analysis of the title compound has established that there is substantial electron delocalisation involving the nitrogen atom and the ester group, with the bonds from the nitrogen atom nearly coplanar. The sulphur atom does not appear to be involved in the conjugation. The crystals are orthorhombic, space group P212121, with Z= 4 in a cell of dimensions a= 8·881 ± 0·005, b= 19·14 ± 0·01, c= 7·042 ± 0·005 A. The structure was determined by Patterson and Fourier methods, by use of three-dimensional counter data, and refined by least-squares to R 6·7% for 1011 structure amplitudes.

Thomas A. Hamor

Papers

Structures of polyfluoroaromatic compounds. V. Crystal structure of perfluorodiphenylacetylene

The crystal structure of pentafluorotropolone

Stereochemistry of anticholinergic agents. Part III. Crystal and molecular structure of piperidolate (N-ethyl-3-piperidyl diphenylacetate) hydrochloride

Crystal and molecular structure of (4R,6R)-3-methoxycarbonyl-9,9-dimethyl-8-oxa-4-thia-1-azabicyclo[4.3.0]non-2-ene 4-oxide

Structure of octafluoro-4,4'-bis(phenylethynyl)biphenyl