Gold(III) Diazonium Complexes for Electrochemical Reductive Grafting

Gold­(III) diazonium complexes were synthesized for the
first time
and studied for electrochemical reductive grafting. The diazonium
complex [CN-4-C6H4NN]­AuCl4 was synthesized by protonating CN-4-C6H4NH2 with chloroauric acid H­[AuCl4]·3H2O to form the ammonium salt [CN-4-C6H4NH3]­AuCl4, which was then oxidized by the one-electron
oxidizing agent [NO]­PF6 in CH3CN. The highly
irreversible reduction potential of 0.1 mM [CN-4-C6H4NN]­AuCl4 observed at −0.06 V versus
Ag/AgCl in CH3CN/0.1 M [Bu4N]­PF6 encompasses
both gold(0) deposition and diazonium reduction. Repeated scans showed
the absence of the reduction peak on the second run, which indicates
that surface modification with a blocking gold aryl film has occurred
and is largely complete.