Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination

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

/pdf/chemical-redox-agents-for-organometallic-chemistry-4fs84ntwp8.pdf

Chemical Redox Agents for Organometallic Chemistry

Strong Closed-Shell Interactions in Inorganic Chemistry.

The ability of platinum and gold catalysts to effect powerful atom-economic transformations has led to a marked increase in their utilization. The quite remarkable correlation of their catalytic behavior with the available structural data, coordination chemistry, and organometallic reactivity patterns, including relativistic effects, allows the underlying principles of catalytic carbophilic activation by π acids to be formulated. The spectrum of reactivity extends beyond their utility as catalytic and benign alternatives to conventional stoichiometric π acids. The resulting reactivity profile allows this entire field of catalysis to be rationalized, and brings together the apparently disparate electrophilic metal carbene and nonclassical carbocation explanations. The advances in coupling, cycloisomerization, and structural reorganization—from the design of new transformations to the improvement to known reactions—are highlighted in this Review. The application of platinum- and gold-catalyzed transformations in natural product synthesis is also discussed.

Catalytic Carbophilic Activation: Catalysis by Platinum and Gold π Acids

Atomically precise pieces of matter of nanometer dimensions composed of noble metals are new categories of materials with many unusual properties. Over 100 molecules of this kind with formulas such as Au25(SR)18, Au38(SR)24, and Au102(SR)44 as well as Ag25(SR)18, Ag29(S2R)12, and Ag44(SR)30 (often with a few counterions to compensate charges) are known now. They can be made reproducibly with robust synthetic protocols, resulting in colored solutions, yielding powders or diffractable crystals. They are distinctly different from nanoparticles in their spectroscopic properties such as optical absorption and emission, showing well-defined features, just like molecules. They show isotopically resolved molecular ion peaks in mass spectra and provide diverse information when examined through multiple instrumental methods. Most important of these properties is luminescence, often in the visible–near-infrared window, useful in biological applications. Luminescence in the visible region, especially by clusters prot...

Atomically Precise Clusters of Noble Metals: Emerging Link between Atoms and Nanoparticles

Publisher Summary The chapter focuses on the compounds containing five or more metal atoms. The slow rate of publication in this area is mainly due to the number of steps required by this research, i.e., synthesis, crystallization, structural identification, and chemical characterization. More than fifty different examples of high nuclearity carbonyl clusters (HNCC) arc presently known, all of which contain Group VIII transition metals. In post-transition metals the increased separation between the (n - 1) d and ns-np orbital is probably responsible for the low stability of their bonds with the highly π-acidic carbon monoxide ligand; a number of high nuclearity clusters with less π -acidic ligands, such as tertiary phosphines or organic donor groups, is known. Approximate calculations on some of the more crowded clusters, such as [Fe 4 (CO) 13 ] 2- , Fe 5 (CO) 15 C, and Ru 6 (CO) 18 H 2 , show that, at the level of the carbon atoms, about 96% of the available surface is occupied. This figure seems very high particularly if the distribution of the carbonyl groups is not considered as homogeneous. The high Nuclearity clusters of the transition metals that precede Group VIII are, therefore, expected to be destabilized by steric crowding, although some carbides and mixed nitrosyl-carbonyl derivatives should be sterically possible.

High Nuclearity Metal Carbonyl Clusters

Five-coordinate alkene complexes of palladium(II) and platinum(II)

New mixed tetranuclear metal carbonyls of group VIIIB

Diiron μ-vinyliminium complexes from acetylene insertion into a metal-aminocarbyne bond

In crystals of Au11I3[P(C6H4-p-Cl)3]7 and in similar species, the metal–metal interactions follow the icosahedral pattern commonly found in intermetallic compounds.

Vincenzo G. Albano

Papers

High Nuclearity Metal Carbonyl Clusters

Five-coordinate alkene complexes of palladium(II) and platinum(II)

New mixed tetranuclear metal carbonyls of group VIIIB

Diiron μ-vinyliminium complexes from acetylene insertion into a metal-aminocarbyne bond

Intermetallic pattern in metal-atom clusters. Structural studies on Au11X3(PR3)7 species