Synthesis, Electrochemistry, XPS, and DFT Calculations of α-Carbon-Bonded Gold(I) Ferrocenyl- and Ruthenocenyl-Containing β-Diketonato Complexes

High Resolution Image Download MS PowerPoint Slide A series of ferrocenyl- and ruthenocenyl-containing β-diketonato (triphenylphosphine)gold(I) complexes of the type [(RCO)(R′CO)-H α C-AuPPh 3 ] were synthesized via the reaction of appropriate β-diketones, RCOC α H 2 COR′, with [(Ph 3 PAu) 3 ][OBF 4 ]. Complexes with R = R′ = CH 3 ( 1 ), or R = Fc = Fe II (η 5 -C 5 H 4 )(η 5 -C 5 H 5 ), and R′ = CF 3 ( 2 ), CH 3 (3 ), Ph = C 6 H 5 ( 4 ), or Fc ( 5 ), as well as R = Ru II (η 5 -C 5 H 4 )(η 5 -C 5 H 5 ) and R′ = CF 3 ( 6 ), CH 3 ( 7 ), Ph ( 8 ), Rc ( 9 ), or Fc ( 10 ), were obtained. The Au– α C bonding mode between gold and β-diketonato ligands was spectroscopically (NMR, FTIR, and XPS) identified as the only bonding mode for all complexes lacking a CF 3 moiety, while a mixture of Au– α C- and Au–( κ O, κ O)-bonded isomers in equilibrium with each other was observed for CF 3 -containing complexes 2 and 6 . This experimental observation is supported by a theoretical study utilizing density functional theory. Cyclic and square wave voltammetric studies in CH 2 Cl 2 /[N( n Bu) 4 ][B(C 6 F 5 ) 4 ] displayed only the metallocene-based redox processes of 2–10 as reversible, well-resolved ferrocenyl and irreversible ruthenocenyl one-electron transfer steps. XPS spectra for each element in the complexes were measured, and an uncommon indirect proportionality between Au 4f 7/2 binding energies and the sum of R group electronegativities, Σχ R, as well as between the Fe 2p 3/2 binding energies and formal ferrocenyl reduction potentials, E °′, was obtained.