Electrochemical behaviour of cyclometallated gold(III) complexes. Evidenceof transcyclometallation in the fate of electroreduced species

Citation
G. Sanna et al., Electrochemical behaviour of cyclometallated gold(III) complexes. Evidenceof transcyclometallation in the fate of electroreduced species, J ORGMET CH, 622(1-2), 2001, pp. 47-53
Citations number
21
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF ORGANOMETALLIC CHEMISTRY
ISSN journal
0022328X → ACNP
Volume
622
Issue
1-2
Year of publication
2001
Pages
47 - 53
Database
ISI
SICI code
0022-328X(20010315)622:1-2<47:EBOCGC>2.0.ZU;2-2
Abstract
The electrochemical behaviour of a series of neutral and cationic N-C and N -N-C cyclometallated gold(III) species: ([Au(py(1))(Cl)(2)], Hpy(1) = 2-ben zylpyridine; [Au(bipy(n))(Cl)][PF6], Hbipy(1) = 6-benzyl-2,2'-bipyridine, H bipy(2) = 6-(1-methylbenzyl)-2,2'-bipyridine, Hbipy(3) = 6-(1,1-dimethylben zyl)-2,2'-bipyridine, Hbipy(4) = 6-phenyl-2,2'-bipyridine) has been investi gated in different solvent systems using cyclic voltammetry and controlled- potential coulometry. All the species considered show, in cyclic voltammetr y, an irreversible one-electron reduction in the potential range -0.9/-1.2 V versus Fc(+/0), using a Pt electrode. On the other hand, exhaustive coulo metries have shown the consumption of a number of Faraday per mole within t he range 1-2. The very complex decomposition of the electrogenerated specie s affords elemental gold and significant amounts of different gold by-produ cts. In some situations (e.g. reduction of [Au(bipy(4))(Cl)][PF6]), working with 0.1 mol dm(-3) Na[PF6], CH3C solvent system, it has been possible to characterise the most abundant gold(III) compound, by NMR, FAB-MS, and elem ental analysis. The analytical and spectroscopic data provide evidence for the N-C bis-cyclometallated gold(III) derivative (e.g. [Au(bipy(4))(2)][PF6 ]); the result entails quite an unusual transcyclometallation process. The same compound can also be obtained, albeit in very minor yield, by chemical reduction of [Au(bipy(4))(Cl)][PF6]. (C) 2001 Elsevier Science B.V. All ri ghts reserved.