197Au Mossbauer spectroscopy

Spectroscopic studies, including vibrational spectroscopy, UV-visible absorption and MCD spectroscopy and 197Au Mossbauer spectroscopy, suggest that isocyanides act largely as a donors to gold(I) with very little d -p back-bonding,69,404,408 It is this polarization R—... 

It will be clear from Table 11 that mixed oxidation state complexes need not contain equal numbers of Au1 and Au111 centres, and fractional oxidation states between I and III may be observed.163,165,300,425 The mixed oxidation state complexes can, in many cases, be distinguished from true Aun complexes by 197Au Mossbauer spectroscopy or by ESCA.4,23,428-429... 

The trans influence can be measured by many techniques, including bond lengths from X-ray structures, bond stretching force constants from vibrational spectroscopy, or from 197Au Mossbauer or NQR parameters. 

The preparation of a successful supported bimetallic catalyst is quite a difficult proposition. The main problem is to ensure that the two components reside in the same particle in the finished catalyst, and to know that it is so. The main physical techniques to characterise bimetallic particles are hydrogen chemisorption, XRD, TEM, EDX, XPS, XAFS,197Au Mossbauer (Section 3.3) and CO chemisorption coupled by IR spectroscopy (Section 5.3). The characterisation of bimetallic catalysts is not always thoroughly done, and there is the further complication of structural changes (particularly of the surface) during use. In situ or post-operative characterisation would reveal them, but it is rarely done. 

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