Gold compounds, isomer shift

Mossbauer studies on gold compounds were first reported by Roberts et al. [337] and Shirley et al. [338, 339]. They observed rather large isomer shift changes in some simple gold (I) and gold (III) halides and in halogeno-complexes such as AuX (X = Cl, Br, I), AuXj (X = F, Cl), K[AuX4] (X = F, Cl, Br), and... 

Fig. 7.78 Linear relation of the quadmpole splitting A q = ( jl)eqQ (1 + j /3)l/2 and the isomer shift b for aurous (a) and auric (b) compounds. Also included is a correlation with the relative change in electron density at the gold nucleus, Ali/r(o)P, as derived from Dirac-Fock atomic structure calculations for several electron configurations of gold. An approximate scale of the EFG (in the principal axes system) is given on the right-hand ordinate (from [341])...

Fig. 7.79 Quadrapole splitting QS versus isomer shift S in gold (I) and gold (III) compounds (from [342])...

Gold-197 Mossbauer Data for the Gold Sites in Gold-Ruthenium Cluster Compounds, in Order of Isomer Shift... 

The Mossbauer data from the quinquevalent gold compounds reported in this paper provide a further basis for the identification of the factors which affect the isomer shift. 

The results for the isomer shift S of the quinque-valent compounds, listed in Column of Table I, are almost identical with each other, supporting the existence of similar AuF anions in all of the studied quinquevalent gold compounds. This has also been concluded from the close similarity of the Raman spectra obtained for these complexes. The results for isomer shift and electric quadrupole splitting found for AuF, agree well with those given in Ref. 4. 

A more quantitative discussion of the isomer shift results of Fig. 2, especially their use for a derivation of an estimate for A(r ), is not straightforward since there are considerable variations in the Au atom coordination in these gold compounds. Au(I) compounds usually contain linear ligand-gold-ligand units in the first coordination sphere, while most of the Au(IIl) complexes have square-planar molecular symmetry. The Au(V) complexes studied in the present work, on the other hand, have octahedral symmetry. ... 

FIG. 2. Graphical representation of Isomer shifts of the 77.3 keV gamma rays of Au for univalent, tervalent, and quinquevalent gold compounds with halogen ligands. 

For a rough estimate of A(r ) we take the isomer shift difference between the AuF complexes and AuFj, AS= 3.4 mm/s, as representative for the one between Au(V) and Au(III). It is obvious from the above discussion that for this pair of gold compounds the difference in effective coordination number is smaller than for any other pair of the stud-... 

Fig. 3.47 Changes in the isomer shift and the electric quadrupole splitting for various gold compounds under pressure. o = Au(l) = Au(lll) (ambient pressure.) = Au(l) = Au(lll) arrows indicate the effect of high pressure. (Reprinted with permission of the publisher.)...

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