Ligand osmium carbonyl derivatives

This observation may well explain the considerable difference between metal-olefin and metal-acetylene chemistry observed for the trinuclear metal carbonyl compounds of this group. As with iron, ruthenium and osmium have an extensive and rich chemistry, with acetylenic complexes involving in many instances polymerization reactions, and, as noted above for both ruthenium and osmium trinuclear carbonyl derivatives, olefin addition normally occurs with interaction at one olefin center. The main metal-ligand framework is often the same for both acetylene and olefin adducts, and differs in that, for the olefin complexes, two metal-hydrogen bonds are formed by transfer of hydrogen from the olefin. The steric requirements of these two edgebridging hydrogen atoms appear to be considerable and may reduce the tendency for the addition of the second olefin molecule to the metal cluster unit and hence restrict the equivalent chemistry to that observed for the acetylene derivatives. 

The Chemical Shifts of the Carbonyl Ligand in Some Derivatives of Manganese, Ruthenium, Osmium, Cobalt,... 

Quinidine [3, (9S)-6 -methoxy-9-cinchonanol] is mostly applied for the same purposes as quinine, such as the addition of zinc alkyls to carbonyl compounds (Section D 1.3.1.4.), or addition of thiophenol to acrylic derivatives (Section D.2.I.). An important technical synthesis of malic acid is based on the quinidine catalyzed enantioselective [2 + 2] cycloaddition of ketene to chloral (see Section D. 1.6.1.3.). Esters and ethers of dihydroquinidine (4) (just like the corresponding derivatives of dihydroquinine) have been used as chiral ligands in osmium tetroxide catalyzed dihydroxylations of alkenes (Section D.4.4.). 

Two significant surveys are published in the sane edition of Coordination Chemistry Reviews. Oxygen donor-ligand derivatives of tri-osmium dodecacarbonyl are covered by Frauenhoff and the reactions of transition metal dihydrogen complexes (of which many are carbonyl-containing) are outlined by Jessop and Morris. The crucial role of matrix Isolation studies is well covered in this article. A shorter review of interest here has been published on the role of the phosphorus d-orbitals in M-P bonding. ... 

Specially straightforward are the mechanistic studies of the acetonitrile derivative of the triosmium carbonyl Os3(CO)n(NCMe) with strong osmium-osmium bonds, inert CO-ligands, and one labile acetonitrile ligand. As mentioned in Sect. 2.4. this kind of light-stabilized intermediate is very useful in the synthesis of substituted derivatives. 

The usefulness of osmium derivatives in nucleic acid chemistry has prompted an investigation of the synthesis and reactions of osmium ligand complexes [e.g. (334)—(336)] of common nucleosides. Such dipyridylosmium esters underwent relatively rapid transesterification reactions with glycols. Other groups have reported n.m.r. studies on the complexes formed between nucleosides and transition-metal carbonyls e.g, [Rh(COa)Cl]2 and W(CO)e and on the ionic binding of Li+ and Cl ions to nucleosides (based on Li and C1 nuclear magnetic relaxation times). ... 

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