For economical and ecological reasons, synthetic chemists are confronted with the increasing obligation of optimizing their synthetic methods. Maximizing efficiency and minimizing costs in the production of molecules and macromolecules constitutes, therefore, one of the most exciting challenges of synthetic chemistry.1-3 The ideal synthesis should produce the desired product in 100% yield and selectivity, in a safe and environmentally acceptable process.4 It is now well recognized that organometallic homogeneous catalysis offers one of the most promising approaches for solving this basic problem.2 Indeed, many of these homogeneous processes occur in high yields and selectivities and under mild reaction conditions. Most importantly, the steric and electronic properties of these catalysts can be tuned by varying the metal center and/or the ligands, thus rendering tailor-made molecular and macromolecular structures accessible.5,6 Despite the fact that various efficient methods, based on organometallic homogeneous catalysis, have been developed over the last 30 years on the laboratory scale, the industrial use of homogeneous catalytic processes is relatively limited.7 The separation of the products from the reaction mixture, the recovery of the catalysts, and the need for organic solvents are the major disadvantages in the homogeneous catalytic process. For these reasons, many homogeneous processes are not used on an industrial scale despite their benefits. Among the various approaches to address these problems, liquidliquid biphasic catalysis (“biphasic catalysis”) has emerged as one of the most important alternatives.6-11 The concept of this system implies that the molecular catalyst is soluble in only one phase whereas the substrates/products remain in the other phase. The reaction can take place in one (or both) of the phases or at the interface. In most cases, the catalyst phase can be reused and the products/substrates are simply removed from the reaction mixture by decantation. Moreover, in these biphasic systems it is possible to extract the primary products during the reaction and thus modulate the product selectivity.12 For a detailed discussion about this and other concepts of homogeneous catalyst immobilization, the reader is referred elsewhere.6,7 These biphasic systems might combine the advantages of both homogeneous (greater catalyst efficiency and mild reaction conditions) and heterogeneous (ease of catalyst recycling and separation of the products) catalysis. The advent of water-soluble organometallic complexes, especially those based on sulfonated phosphorus-containing ligands, has enabled various biphasic catalytic reactions to be conducted on an industrial scale.13-15 However, the use of water as a * Corresponding author. Fax: ++ 55 51 3316 73 04. E-mail: dupont@iq.ufrgs.br. 3667 Chem. Rev. 2002, 102, 3667−3692

https://www.chem.ccu.edu.tw/~joyce/referance/gump/IL/Chem.%20Rev.%202002,%20102,%203667.pdf

Ionic liquid (molten salt) phase organometallic catalysis.

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

Synthesis of 3d metallic single-molecule magnets

The manganese and calcium ions of photosynthetic oxygen evolution.

The magnetic properties of many magnetic materials can be controlled by external stimuli. The principal focus here is on the thermal, photochemical, electrochemical, and chemical control of phase transitions that involve changes in magnetization. The molecular compounds described herein range from metal complexes, through pure organic compounds to composite materials. Most of the Review is devoted to the properties of valence-tautomeric compounds, molecular magnets, and spin-crossover complexes, which could find future application in memory devices or optical switches.

Control of magnetic properties through external stimuli.

Polarographic and magnetic susceptibility study of various biferrocene compounds

Intramolecular two-electron transfer between manganese(II) and semiquinone ligands. Synthesis and characterization of manganese 3,5-di-tert-butylquinone complexes and their relationship to the photosynthetic water oxidation system

The preparation and characterization of the first Fe II spin-crossover complex that interconverts between high- and low-spin states at a rate faster than the 57 Fe Mossbauer time scale is reported. [Fe(tpen)](ClO 4 ) 2 .2/3H 2 O crystallizes in the monoclinic space group C2/c.

(Tetrakis(2-pyridylmethyl)ethylenediamine)iron(II) perchlorate, the first rapidly interconverting ferrous spin-crossover complex

Synthesis, physical properties, and crystal structure of the cubane compound bis(.mu.-acetato)-tetra-.mu.-methoxo-bis[.mu.-(2,5-dimethyl-2,5-diisocyanohexane)]-tetranickel(II) tetraphenylborate

The photochemistry of metalloporphyrins and related macrocycles is of intense current interest. Nonetheless, the photochemistry of ferric porphyrins and heme proteins remains largely unexplored and not well understood. The ability of Fe(III) porphyrins to act as catalysts for hydrocarbon oxidations with various oxidants suggested to us their possible use as photocatalysts. In this paper, they assign a near-ultraviolet absorption in Fe/sup III/(TPP)(X) (where X = F, Cl, Br, I, N/sub 3/; TPP = 5,10,15,20-tetraphenylporphyrinate(-2)) as a halide ligand-to-metal charge-transfer (LMCT) transition. Irradiation into this band leads to rapid photoreduction of the iron atom and dissociation of X/sup 0/. In the presence of O/sub 2/, photoinitiation of hydrocarbon oxidation occurs.

David N. Hendrickson

Papers

Polarographic and magnetic susceptibility study of various biferrocene compounds

Intramolecular two-electron transfer between manganese(II) and semiquinone ligands. Synthesis and characterization of manganese 3,5-di-tert-butylquinone complexes and their relationship to the photosynthetic water oxidation system

(Tetrakis(2-pyridylmethyl)ethylenediamine)iron(II) perchlorate, the first rapidly interconverting ferrous spin-crossover complex

Synthesis, physical properties, and crystal structure of the cubane compound bis(.mu.-acetato)-tetra-.mu.-methoxo-bis[.mu.-(2,5-dimethyl-2,5-diisocyanohexane)]-tetranickel(II) tetraphenylborate

Photochemistry of (5,10,15,20-tetraphenylporphyrinato)iron(III) Halide complexes, Fe(TPP) (X)