Osmium complexes, photolysis

Recently, we have studied such a photoredox reaction (6) that proceeds in analogy to the photolysis of the binuclear osmium complex Eq. (23) ... 

Osmocene is a photoactive compound. Photolysis of osmocene in n-hexane led to metallic osmium by reductive elimination. In the LF excited triplet state, osmocene undergoes a distortion by bending, which facilitates the transfer of a CH group between the cyclopentadienyl ligands. The resulting intermediate is an osmium complex with benzene and cyclobutadiene ligands, that decomposes to osmium metal, benzene and cyclobutadiene. ... 

Photoinduced and chemical oxidation of coordinated imines to amides in isomeric osmium(II) complexes of AT-arylpyridine-2-carboxaldimines has been studied by Ghosh and coworkers [34]. The complexes [Os(Br)2(Rimpy)2] (Scheme 1) were prepared and characterized structurally, indicating the pyridines of the two Rimpy ligands are trans to one another and the bromides are cis. Broadband photolysis of the complex in aerated acetonitrile resulted in oxidation of one Rimpy ligand to yield the RimOpy ligand and oxidation of the osmium to Os(III). The overall yield of the photochemical process is reported to be greater than 95%. The authors propose a mech-... 

A binuclear bis(/z-germylene) osmium carbonyl complex [(OC)4Os(GeMe2)]2 on photolysis or thermolysis yields a mixture of an interesting series of (/z-germylene) osmium clusters36. Bis(metalcarbonyl)germacyclopentene complexes on photolysis or thermolysis... 

In addition to metal-yne n complexation, Pu and co-workers (522) synthesized and crystaUographically characterized a water soluble, metal-ene n-complex by reacting [Os(en)2H2H20] with a TMS-substituted enediyne (TMS=Tetramethylethylene). The X-ray structure shows q -enediyne complexation to osmium (Scheme 79), however, no metal-promoted Bergman cyclization reactivity is observed, and only enediyne dissociation occurs upon oxidation or photolysis of the metal complex. 

Photochemical reactions of Ru3(CO)i2 and Os3(CO)i2 with nitrogen hetero-cycles have been studied, with substitution products being formed in most cases. For example, with pyridine the ruthenium compound forms the ortho-metallated complex Ru3H(CO)i i(CsH4N), while the osmium compound gives the simple substitution product Os3(CO)n(py). The novel dihydrido triruthenium cluster H2Ru3(CO)io can be synthesized by photolysis of Ru3(CO)i2 under an atmosphere of dihydrogen. 

The alkenyl-osmium(ii) derivative [OsH(GH=GH2)(77 -l,3,5-G6H3Me3)(GNMe)] has been obtained by photolysis of the ethene-Os(ii) complex [Os(77 -GH2=GH2)(77 -l,3,5-G6H3Me3)(GNMe)] via intramolecular oxidative G-H addition. " A new activation of propargylic alcohols, leading to the formation of alkenyl oxametallacycles... 

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