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Synthesis, Structure, and Electrochemical Studies of μ3-η2,η2,η2-C60 Triosmium Complexes
journal contribution
posted on 1998-09-09, 00:00 authored by Hyunjoon Song, Kwangyeol Lee, Joon T. Park, Moon-Gun ChoiTwo μ3-η2,η2,η2-C60 complexes, Os3(CO)8(PPh3)(μ3-η2,η2,η2-C60) (8) and Os3(CO)7(PMe3)2(μ3-η2,η2,η2-C60) (9), have been prepared by decarbonylation of Os3(CO)9(μ3-η2,η2,η2-C60) (6) with
Me3NO/MeCN in the presence of phosphine ligands. The molecular structure of 8 has been
determined by a single-crystal X-ray diffraction study. The structure of 8 is derived from
that of Os3(CO)11(PPh3) by replacing three axial carbonyl ligands with a μ3-face-capping C6
ring of C60. The 13C NMR spectra (C60 region) of 6 and Os3(CO)8(PMe3)(μ3-η2,η2,η2-C60) (7)
show 11 sp2 and 1 sp3 carbon resonances and 29 sp2 and 3 sp3 carbon resonances, respectively,
which are consistent with C3v and Cs symmetric nature of the two complexes in solution.
Electrochemical properties of 6, 7, and 9 have been studied by cyclic voltammetry (CV) in
1,2-dichlorobenzene (DCB) solutions. The general features of CV curves have revealed four
reversible redox couples for 6 and 7 and three for 9 in the DCB potential window. The
μ3-η2,η2,η2-C60 complexes, 6, 7, and 9, show a remarkable electrochemical stability compared
to the known η2-C60 triosmium carbonyl complexes. The CV results suggest that a C60-mediated electron transfer to the triosmium center takes place in 6 and 7, but three successive
C60-localized reductions occur in 9.