Osmium complexes, mixed

Most of the reports of osmium complexes containing 1,1-dithio ligands are concerned in the use of dithiocarbamate complexes for the analytical determination of the metal (296) a violet color forms when OSO4 and NaR2dtc are mixed in aqueous solution (84). 

The infrared, NMR, and electronic absorption spectra of the two complexes H2FeRu2Os(CO)i3 and H2FeRuOs2(CO)13 have been taken to indicate a structure for these compounds similar to H2FeRu3(CO)13. However, the infrared and low-temperature proton NMR spectra of both compounds indicate that they exist as a mixture of isomers the two projected isomers for H2FeRu2Os(CO)13 are shown in Fig. 58 (247). The mixed manganese and rhenium-osmium complexes, H3MOs3(CO)13, have been prepared by acidification of the reaction mix-... 

Factors affecting simple reductive elimination versus other forms of elimination (e.g. a), especially with respect to dihydrides, dialkyls, and mixed alkyl-hydrides (which eliminate fastest) of mono- and di-nuclear osmium complexes, have been discussed. In compounds such as [OsHMe(CO)4] or [OsMe2(CO)4] simple reductive elimination does not occur for example, a mixture of [OsH(CD3)(CO>4] and [OsD(CH3)(CO)4] gave CH4, CH3D, CD3H, and CD4, and a dinuclear mechanism is proposed. ... 

ECL of Ir(ppy)3/TPA [79] and Os(phen)2(dppene) /TPA [88] in the presence of Triton X-100 were also smdied. An osmium complex, Os(phen)3, was the first osmium complex that gave ECL response using S20g reduction to generate the excited state [89]. A series of osmium complexes containing bpy and phen ligands showed ECL enhancement via annihilation [10]. While using TPA as coreactant [90], Os(phen)2(dppene) exhibits ECL in aqueous and mixed aqueous/ nonaqueous solutions. Osmium polypyridine complexes have also been studied [88, 89]. 

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. 

Ruthenium(IV) produces few other complexes of interest but osmium(IV) yields several sulfito complexes (e.g. [0s(S03)6] and substituted derivatives) as well as a number of complexes, such as [Os(bipy)Cl4] and [Os(diars)2X2] (X = Cl, Br, I), with mixed halide and Group 15 donor atoms. The iron analogues of the latter complexes (with X = Cl, Br), are obtained by oxidation of... 

The actual catalyst is a complex formed from osmium tetroxide and a chiral ligand, e.g. dihydroquinine (DHQ) 9, dihydroquinidine (DHQD), Zj -dihydroqui-nine-phthalazine 10 or the respective dihydroquinidine derivative. The expensive and toxic osmium tetroxide is employed in small amounts only, together with a less expensive co-oxidant, e.g. potassium hexacyanoferrate(lll), which is used in stoichiometric quantities. The chiral ligand is also required in small amounts only. For the bench chemist, the procedure for the asymmetric fihydroxylation has been simplified with commercially available mixtures of reagents, e.g. AD-mix-a or AD-mix-/3, ° containing the appropriate cinchona alkaloid derivative ... 

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