Osmium complexes reviews

Diols are applied on a multimilhon ton scale as antifreezing agents and polyester monomers (ethylene and propylene glycol) [58]. In addition, they are starting materials for various fine chemicals. Intimately coimected with the epoxidation-hydrolysis process, dihydroxylation of C=C double bonds constitutes a shorter and more atom-efficient route to 1,2-diols. Although considerable advancements in the field of biomimetic nonheme complexes have been achieved in recent years, still osmium complexes remain the most efficient and reliable catalysts for dihydroxylation of olefins (reviews [59]). 

The potential of osmium complexes as homogeneous catalysts has been highlighted in two recent reviews.100,101... 

Application of computaional methods to the enantioselective dihydroxylations of alkenes by osmium complexes have been reviewed with a special focus on methods used to study the origin of high enantioselectivity. The use of a vast number of computational techniques such as QM, MM, Q2MM, QM/MM, molecular dynamics, and genetic algorithms has been enumerated.98... 

This article is intended to review the published work on the photochemistry and photophysics of osmium complexes that has appeared in the literature over the past several years. We have attempted to cover, albeit somewhat selectively, literature dating back to the year 2000. A variety of reviews pertaining to particular aspects of osmium photophysics and photochemistry were published prior to 2000. A few reviews discuss the photophysical behavior of primarily monometallic Os complexes in solution [1,2]. Several earlier reviews discuss light induced energy and electron transfer reactions involving osmium complexes in much of this work the Os complex is not the chro-mophore [3-6]. Finally, one review exists discussing the photochemistry of Os carbonyl complexes [7]. 

Osmium-catalysed dihydroxylation has been reviewed with emphasis on the use of new reoxidants and recycling of the catalysts.44 Various aspects of asymmetric dihydroxylation of alkenes by osmium complexes, including the mechanism, acceleration by chiral ligands 45 and development of novel asymmetric dihydroxylation processes,46 has been reviewed. Two reviews on the recent developments in osmium-catalysed asymmetric aminohydroxylation of alkenes have appeared. Factors responsible for chemo-, enantio- and regio-selectivities have been discussed.47,48 Osmium tetraoxide oxidizes unactivated alkanes in aqueous base. Isobutane is oxidized to r-butyl alcohol, cyclohexane to a mixture of adipate and succinate, toluene to benzoate, and both ethane and propane to acetate in low yields. The data are consistent with a concerted 3 + 2 mechanism, analogous to that proposed for alkane oxidation by Ru04, and for alkene oxidations by 0s04.49... 

There are several recent and comprehensive reviews on metal nitrosyl complexes which give good coverage to the osmium complexes 198 a review on ruthenium nitrosyl complexes is particularly... 

The porphyrin ligands impose an N4 plane on their complexes and, by virtue of the extensive aromaticity of the ligand, are effective it acceptors. Thus it is that most of the osmium complexes are octahedral and of the form t/ww-Os fporphyri Lj or -OsH(porphyrin)LL. Most of the work on osmium complexes has been carried out by Buchler and his collaborators using the octaethylpor-phyrin (OEP2-) ligand. There are two reviews on the subject.889,890... 

Reviewed in this section is the chemistry of Os3(CO),2, OsH2Cl2(P Pr3)2, Os(/ -MeC6H4CHMe2)(N Bu), NaiOsCl, 0s04and osmium carbene complexes. Reviews of other osmium complexes are available [224-225]. 

A wide range of ruthenium and osmium complexes incorporating metallated pincer phosphines or pincer amines have been prepared and characterized and used in applications ranging from materials to catalysis. These will not be reviewed in great detail here—for information, readers are referred to the following citations. ... 

The chemistry of alkynyl-metal complexes has been reviewed recently.Glassical synthetic routes to half-sandwich alkynyl-ruthenium and alkynyl-osmium complexes of general composition [M(G=GR)(77 -G7,Ht )(L )(L )] are based on the reactions of appropriate halide precursors with lithium/sodium alkynyl reagents or... 

Aspects of this area have been reviewed by Creutz/ A number of new binuclear ruthenium and osmium complexes which can exist in mixed-valence form have been reported/ " The ligand 2,2, 3,3 -tetra-2-pyridyl-6,6 -biquinoxaline allows attachment of up to four Ru(II)(bipy)2 fragments. The molecule appears to act as two independent subunits which can exist in mixed-valence forms. Intervalence transfer (IT) bands detected for these mixed-valence subunits allow calculation of an electron transfer rate of 1 X 10 s" between the metal centers 6.8 A apart. 

Reactions of of high oxidation state osmium and Ru polypyridyl complexes have been reviewed [43]. 

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