Electrochemistry of Carbidopentaruthenium C60 Complexes and Related Clusters

Abstract

The electrochemical behavior of the face-coordinated C 6 0 -carbidopentaruthenium cluster complexes Ru 5 C(CO) 1 1 (PPh 3 )(μ 3 -η 2 ,η 2 ,η 2 -C 6 0 ) (1), Ru 5 C(CO) 1 0 (μ-η 1 ,η 1 -dppf)(μ 3 -η 2 ,η 2 ,η 2 -C 6 0 ) (2) (dppf = 1,1'-bis(diphenylphosphino)ferrocene), and PtRu 5 C(CO) 1 1 (η 2 -dppe)μ 3 -η 2 ,η 2 ,η 2 -C 6 0 ) (3) (dppe = 1,2-bis(diphenylphosphino)ethane) has been examined by cyclic voltammetry, rotating disk electrode voltammetry, and differential pulse voltammetry methods. The behavior of compounds Ru 5 C(CO) 1 5 (4), Ru 5 C(CO) 1 4 (PPh 3 ) (5), Ru 5 C(CO) 1 3 (μ-η 1 ,η 1 -dppf) (6), PtRu 5 C(CO) 1 6 (7), and PtRu 5 C(CO) 1 4 (η 2 -dppe) (8) was studied also for comparison. For both 1 and 3, the voltammetric scans show an initial irreversible two-electron reduction feature, followed by three quasi-reversible, one-electron reductions of the C 6 0 ligand. In contrast, similar scans for 2 indicate an initial quasi-reversible, one-electron reduction of the C 6 0 ligand that is dynamically coupled with a second one-electron, irreversible reduction. Stepwise reduction of the C 6 0 ligand proceeds at more negative potentials. Interpretation of the electrochemical behavior of compounds 1-8 has been enhanced by studying their chemical reduction with cobaltocene. In all cases uptake of two electrons results in irreversible loss of a CO ligand from the cluster, and the resulting dianionic complexes have been characterized by their IR (ν C O ) spectra.