Gold V Complexes

A number of complexes containing the low spin d ion, AuF (Au-F 1.86 A) have been made [143]. 

AuF5 is formed on heating M AuF (M = NO, O2) there has been interest in synthesizing AuF by oxidation of AuF but it is likely that the t2g configuration is too stable to be oxidized. 

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The first pure gold(V) complex to be prepared was [Xe2Fn][AuF6], formed by reaction of AuF3 with fluorine and XeF2.58 The [AuF6] ion is approximately octahedral with r(AuF) 186 pm.647... 

In this account, the new oxidation states are introduced in the format of a short, but it is hoped complete, summary covering the literature until late 1980. Some of the topics were reviewed previously, but the articles soon became out-dated because of the rapid growth of the fields. Best known are the discussion of gold(II) compounds (23) and the early presentation of gold(V) complexes (5). Gold clusters have been included in the leading reference texts on gold chemistry (77, 85), and the -1 state appeared in a recent summary on liquid metals and liquid semiconductors (39). 

Only fluoride compounds of Au are known, and they all have octahedral stereochemistry as expected for a d metal ion. Reaction between AuFs, fluorine, and Xep2 yielded the first gold(V) complex [XeFu][AuF6] (equation (14)). 

One might have expected oxo-anions [16] of Kr(VI) or Kr(VIII) (Br04 was prepared in 1968), but the only well-characterized krypton compounds are the rather unstable linear molecule FKrF and the Kr(II) salts such as KrF SbFg and KrF" AuFg containing an octahedral 5d gold(V) complex anion. There are good reasons to believe from quantum mechanical calculations (see Sect. 4.3 of... 

FIGURE 3.16 The structure of a gold(V) complex, Au F5. (Data from Gold pentaflouride structure and fluoride ion affinity, I-C. Hwang and K. Seppelt, Angew. Chem. Int. Ed., 2001, 40, 3690.)... 

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