Anthracene charge*transfer osmylation

Charge-transfer Osmylation cf Benzene, Naphthalene and Anthracene... 

Most importantly, both in the thermal and the charge-transfer osmylation of anthracene, identical cycloadducts on the terminal ring are observed, which underscores the close relationship between the two reaction modes. Thus, a unifying electron-transfer mechanism is proposed for both thermal and photoactivated osmylation, which reveals the ion-radical pair [Ar+ , 0s04 ] as the common (primary) reactive intermediate [161]. 

Photochemical osmylation. The irradiation of the charge-transfer bands (Fig. 13) of the EDA complex of 0s04 with various benzenes, naphthalenes, anthracenes, and phenanthrene yields the same osmylated adducts as obtained in the thermal reactions. For example, irradiation of the purple solution of anthracene and 0s04 in dichloromethane at k > 480 nm yields the same 2 1 adduct (B) together with its syn isomer as the sole products, i.e.,... 

Note that the charge-transfer irradiation of the same anthracene/Os04 complex in hexane solution yields only a small amount of the adduct (B) together with considerable amounts of anthraquinone. The latter probably arises from osmylation at the (9,10) positions followed by decomposition of the unstable osmium adduct.218... 

Molecular complexes of OSO4 with various substituted benzenes, naphthalenes, and anthracenes have been identified by their charge-transfer absorption, which follows the Mulliken correlation in Eq. 8 [114, 161], The arene-0s04 complexes are quite stable when kept in the dark and only very slowly form osmium(VI) cycloadducts by thermal osmylation (Eq. 30). 

---