Evaluating electrochemical accessibility of 4fn5d1 and 4fn+1 Ln(ii) ions in (C5H4SiMe3)3Ln and (C5Me4H)3Ln complexes

The reduction potentials (reported vs. Fc(+)/Fc) for a series of Cp '(3)Ln complexes (Cp ' = C5H4SiMe3, Ln = lanthanide) were determined via electrochemistry in THF with [(Bu4N)-Bu-n][BPh4] as the supporting electrolyte. The Ln(iii)/Ln(ii) reduction potentials for Ln = Eu, Yb, Sm, and Tm (-1.07 to -2.83 V) follow the expected trend for stability of 4f(7), 4f(14), 4f(6), and 4f(13) Ln(ii) ions, respectively. The reduction potentials for Ln = Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu, that form 4f(n)5d(1) Ln(ii) ions (n = 2-14), fall in a narrow range of -2.95 V to -3.14 V. Only cathodic events were observed for La and Ce at -3.36 V and -3.43 V, respectively. The reduction potentials of the Ln(ii) compounds [K(2.2.2-cryptand)][Cp '(3)Ln] (Ln = Pr, Sm, Eu) match those of the Cp '(3)Ln complexes. The reduction potentials of nine (C5Me4H)(3)Ln complexes were also studied and found to be 0.05-0.24 V more negative than those of the Cp '(3)Ln compounds.

Automated summary

In this study, the reduction potentials of a series of Cp'(3)Ln complexes with different lanthanide elements were determined electrochemically. The results showed a clear trend in the reduction potentials of Ln(iii)/Ln(ii) ions, indicating different stabilities among different lanthanide ions.