Redox behavior of the molybdenum and tungsten metallafullerenes M(η2-C60)(CO)2(phen)(dbm) (phen = 1,10-phenanthroline; dbm = dibutyl maleate): (spectro)electrochemistry and theoretical considerations

Abstract

Electrochemistry of M(η 2 -C 60 )(CO) 2 (phen)(dbm) (M = W 1, Mo 2; phen = 1,10-phenanthroline; dbm = dibutyl maleate) shows that the complexes undergo four sequential reduction processes. As with free C 60 , the first three electrons add reversibly (even if the relevant potentials are shifted ca. 0.15 V toward negative values), whereas the fourth reduction features chemical irreversibility. Cyclic voltammetry gives evidence that, as a consequence of the latter process, the metal fragment decomplexes and [C 60 ] 3Ϫ is released. In good agreement with this picture, a qualitative MO approach shows four close LUMOs for the ground state structure of the uncharged complexes. The first three levels are delocalized over C 60 (somewhat extended to the dmb π system), while the fourth one is metalfullerene antibonding (back donation d π → π* C 60 ) and its occupation causes fulleride dissociation. The EPR spectra of the electrogenerated [1] Ϫ and [2] Ϫ monoanions are significantly different from that of [C 60 ] Ϫ and seem suggestive of metal character for these radical species. At present, this result is unexpected in that the unpaired electron in the anions [1] Ϫ and [2] Ϫ should be intuitively centered on the coordinated fullerene.

Photophysical and Electrochemical Characterisation of the Interactions between Components in Neutral π-Associated [2]Catenanes

“…[23] All the potential values are expressed with reference to the saturated calomel electrode (SCE); under the experimental conditions the reversible one-electron oxidation of ferrocene occurs at 0.37 V. For aromatic diimides 1 ± 5 the application of controlled potential coulometry to the first reduction step reveals the consumption of one-electron per molecule. For the catenanes the number of electrons involved in the second two-electron reduction is inferred from the CV profile, controlled potential coulometry failed as an electron-counting test owing to decomposition of the electrogenerated anions to further reducible by-products.…”

Discrete Fulleride Anions and Fullerenium Cations

“…In most cases the fulleride anion dissociates readily, particularly as successive reductions take place, but ex- -have been reported. 444,445 Electrochemical reduction of Pd(PHCN) 2 Cl 2 /C 60 in toluene/acetonitrile produces black polymeric films which are believed to have the composition C 60 Pd x . 446 Related chemistry occurs with low-valent Rh and Ir complexes.…”

Reactions of the B‐Phenylborole Complex [CpRh(η5‐C4H4BPh)] with Metalloelectrophiles [(ring)M]2+

“…The isolation of products was conducted in air. Starting materials 2, [21] [Cp*CoCl 2 ] 2 , [22] [Cp*RhCl 2 ] 2 , [23] [ [26] Unless otherwise specified, potential values are referred to the Saturated Calomel Electrode (SCE). Under the present experimental conditions, the one-electron oxidation of ferrocene occurs at E°Ј = +0.39 V. The UV/Vis spectroelectrochemical measurements were carried out using a Perkin-Elmer Lambda 900 UV/Vis spectrophotometer and an OTTLE (optically transparent thin-layer electrode) cell [27] equipped with a Pt minigrid working electrode (32 wires/cm), a Pt minigrid auxiliary electrode, an Ag wire pseudoreference and CaF 2 windows.…”