Heteronuclear Gold Cluster Compounds

Electrochemical investigations of [Au2Re2(H)6(PPh3)6](PF6) have shown that this cluster displays a rich redox chemistry (244) and it has been concluded that the existence of this reversible electron transfer chemistry is due to the considerable amount of Re-Re multiple bond character that is retained in the cluster. A number of gold-osmium cluster compounds have been reported to show reversible redox chemistry (245). 

Single-crystal X-ray crystallography remains the only definitive technique for the structural characterization of heteronuclear gold cluster compounds, although other techniques, in particular Mossbauer, NMR, IR, and fast atom bombardment mass spectroscopies (FABMS), have yielded valuable information, especially concerning the nature of these species in solution. Electron spectroscopy, which has proved to be of great value in the identification of homonuclear gold cluster compounds (210) has received little attention by workers in this area, 

The following sections summarize the applications of fast atom bombardment mass spectrometry, Mossbauer and NMR spectroscopies, and single-crystal X-ray diffraction studies in the characterization of het-eronuclear gold cluster compounds. 

Fast atom bombardment mass spectroscopy has proved to be most useful when applied to the characterization of heteronuclear gold cluster compounds containing hydride ligands (137,149,155). Characterization is aided by the observation that peaks are invariably present in the spectrum corresponding to ions that contain all of the hydride 

Good correlations have been observed between the measured Mossbauer parameters and the gold-ruthenium bond lengths and the con- 

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Heteronuclear Gold Cluster Compounds D. Michael P. Mingos and Michael J. Watson... 

Decene complexes with gold, 12 348 Deformation density, 27 29-33 Degradation reactions, heteronuclear gold cluster compounds, 39 336-337 Dehydration reactions, osmium(II), 37 351 Delocalization, see also Valence delocalization added electron, reduced dimer, 38 447, 449 optical centers, interaction with surroundings, 35 380 Density... 

Electric fleld gradient, 22 214-218 Electroabsorption spectroscopy, 41 279 class II mixed-valence complexes, 41 289, 291, 294-297 [j(jl-pyz)]=+, 41 294, 296 Electrocatalytic reduction, nickel(n) macro-cyclic complexes, 44 119-121 Electrochemical interconversions, heteronuclear gold cluster compounds, 39 338-339 Electrochemical oxidation, of iron triazenide complexes, 30 21 Electrochemical properties fullerene adducts, 44 19-21, 33-34 nickeljll) macrocyclic complexes, 44 112-113... 

Familial amyotrophic lateral sclerosis, superoxide dismutase and, 45 148 Fano resonance, 35 349-350 Fast atom bombardment mass spectrometry, heteronuclear gold cluster compounds, 39 340-342... 

Francium, binary carbide not reported, 11 210 Franck-Condon effect, 16 69 energy, 21 180, 188, 189 envelopes, 16 80, 89, 90 hot bands, 16 90 factors, 32 47 principle, 21 179, 181 vibronic replica, 35 370 frd redon, 38 412, 414 Freeze quench EPR spectroscopy (FQ-EPR), CODH/ACS, 47 318 Fremy s salt, 33 106 Friedel-Crafts reaction, 17 194 cyclophosphazene, 21 65, 66 Frontier molecular orbitals, heteronuclear gold cluster compounds, 39 378-381 Frozen solutions, MOssbauer spectra in studies of, 15 101-103... 

NMR spectra heteronuclear gold cluster compounds, 39 345-348 Phalaris canariensis esophageal cancer, 36 144-145 scanning proton microprobe, 36 149 structural motifs of silicas, 36 146 Pharmaceuticals, 18 177 Phase transitions, in chalcogenide halide compounds, 23 332, 408, 412 [PhCHjMejNAlHjlj, 41 225-226 [(PhCH2)jNLi]3 molecular structure, 37 94, 96 in solution, 37 107-108... 

IV. Structure and Bonding in Heteronuclear Gold Cluster Compounds... 

V. Applications of Heteronuclear Gold Cluster Compounds References... 

The addition of gold phosphine fragments to transition metal compounds is readily extended to include reactions of heteronuclear gold cluster compounds and has been used to build up clusters of increasing nuclearity, as the following examples illustrate ... 

Changes in cluster nuclearity have also been observed to accompany the addition of acid or base to heteronuclear gold cluster compounds and may result in aggregation, as in the reactions... 

Electrochemical interconversion of homo- and heteronuclear gold cluster compounds remains an area that has received scant attention, despite the potential for changing the electron count and hence the metal cage geometries of these clusters by electrochemical methods. The electrochemical redox reactions of [Pt(AuPPh3)8]2+ have been studied, using pulse, differential pulse, and cyclic voltammetric techniques (124, 242) and two reversible, one-electron reduction steps have been... 

The 31P H NMR spectra of a number of heteronuclear gold cluster compounds are found to be deceptively simple and NMR studies have been used as a probe of the behavior of these species in solution. This is especially true of the higher nuclearity clusters, which often exhibit spectra that are much simpler than would be predicted on the basis of their solid-state structures. For example, [Pt(H)(PPh3)(AuPPh3)7]2+, which adopts the solid-state structure illustrated in Fig. 9 (137) in which the phosphine ligands occupy several different chemical environments within the molecule, shows only two resonances in the 31P 1H NMR spectrum. These are in a ratio of 7 1 and exhibit satellites due to coupling to the central platinum nucleus as Fig. 10 illustrates. 

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