Compounds in High Oxidation States

There is a vigorously expanding chemistry of compounds of ruthenium and osmium in high oxidation states [3, 4, 11, 12], particularly of dioxo and nitrido compounds, though recently some striking developments have taken place in imide chemistry. 

The osmium MO compounds are much more numerous and have greater stability. 

The first component to be identified was the yellow ammine (Fremy, 1844)  

Compounds that are O- and N-donors like oxalate and ethylenediamine are able to support the +6 oxidation state 

Osmate esters are important intermediates in the reactions of 0s04 in the stereospecific m-hydroxylation of alkenes and other unsaturated molecules [182], 

0s04 H2C2°4 M20s02(C204)2 (M = alkali metal) 

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Later Schrock showed that compounds in high oxidation states, for example, Cl2H(PR3)3Tav(CHCMe3), with fewer than 18 electrons could be made by a-hydro-gen loss from an alkyl group. These have been termed alkylidene complexes. Informally, the two types are often called Fischer carbenes and Schrock carbenes. The IUPAC recommends calling them all alkylidene complexes, with the term carbene being restricted to a free CR2 species. 

Rhenium compounds in high oxidation states often contain multiply bonded [Re N], [Re 0], and [Re Oj] units. It is clearly desirable to have large-scale, convenient preparations of these compounds. Although the nitrido-rhenium complex featured here, ReNCl2(PPh3)2, is a key starting material, a detailed preparation has not been published previously. This new, versatile preparation is based quite closely on previous preparations and chemical observations. 

Atom-transfer-type oxidation reactions can occur by electrophilic, nucleophilic, or radical pathways. Electrophilic mechanisms are prevalent with metal compounds in high-oxidation states. Common among these reagents are oxo complexes of Mn(VII), Cr(VI), V(V), as well as organic... 

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