An electrochemical and spectroelectrochemical study of an iridium-buckminsterfullerene complex: evidence for C60-localized reductions

Electrochemical Studies of C60−Triosmium Complexes: First Evidence for a C60-Mediated Electron Transfer to the Metal Center

“…Half-wave potentials (E 1/2 ) of 1-3 and other known C 60 complexes are summarized in Table 1. The fast scan CV (a) exhibits two reversible reduction waves at E 1/2 ) -1.08 and -1.31 V. The first reduction wave at E 1/2 ) -1.08 V of 1 is slightly more negative than that of free C 60 at -1.05 V, which is consistent with the metal-to-C 60 π-backdonation as was shown in other previous C 60 -metal complexes 3,4 (see Table 1). The direct metal center reductions of Os 3 (CO) 12 (4) and Os 3 (CO) 11 (η 2 -dmfu) 7 (5, dmfu ) trans-MeO 2 CHCd CHCO 2 Me) have been observed at far more negative potentials, -2.02 V for 4 and -1.71 V for 5 under conditions identical to those for 1.…”

“…10 If an electron is localized on the C 60 ligand, a small shift in ν CO (∼10 cm -1 ) is expected. 3 The IR spectroelectrochemical study of 2 -reveals a similar change but very poorly defined spectrum, and thus an electron transfer mechanism analogous to that of 1 -seems to occur. However, the IR spectrum of 3 -during the spectroelectrochemical study remains the same as that of 3.…”

“…Reduction of triosmium carbonyl complexes by one electron typically results in a change in ν CO on the order of ∼50 cm -1 . If an electron is localized on the C 60 ligand, a small shift in ν CO (∼10 cm -1 ) is expected …”

“…1 The electrochemistry of C 60 itself has been extensively studied, and free C 60 is known to be a fairly electronegative carbon cluster being reducible up to C 60 6-. 2 However, little is known about the electrochemical properties of organometallic C 60 derivatives, although a few examples have appeared for (η 5 -C 9 H 7 )Ir(CO)-(η 2 -C 60 ) 3 and [(Et 3 P) 2 M] n (η 2 -C 60 ) (M ) Ni, Pd, Pt; n ) 1-4) 4 complexes, which revealed C 60 -localized sequential reductions. Some of us have recently characterized C 60 -triosmium complexes, 5 Os 3 (CO) 11 (η 2 -C 60 ) (1), 6 Os 3 (CO) 10 (PPh 3 )(η 2 -C 60 ) (2), and Os 3 (CO) 9 (PPh 3 ) 2 (η 2 -C 60 ) (3).…”

Discrete Fulleride Anions and Fullerenium Cations

“…Nevertheless, electroreduction of fullerene complexes typically allows the observation of radical anion complexes, at least on the time scale of cyclic voltammetry. 442,443 Because three reduction waves can frequently be observed, equally spaced but displaced by ca. 0.2 V from those of C 60 , the added electron can safely be assumed to reside predominantly on the fullerene.…”