Electrochemical Evidence for Hemilabile Coordination of 1,3-Dimethyllumazine to [1,1′-Bis(diorganophosphino)ferrocene]copper(I)
datasetposted on 22.09.2014, 00:00 by Rajkumar Jana, Biprajit Sarkar, Sabine Strobel, Shaikh M. Mobin, Wolfgang Kaim, Jan Fiedler
The complex cations [Cu(dippf)(DML)]+ (+) and [Cu(dppf)(DML)]+ (+), where dippf = 1,1′-bis(diisopropylphosphino)ferrocene, dppf = 1,1′-bis(diphenylphosphino)ferrocene, and DML = 1,3-dimethyllumazine, were prepared and crystallized as BF4– or PF6– salts. Structure determinations of the tetrafluoroborates revealed asymmetric O4,N5 chelation of DML to copper(I) with longer Cu–O bonds of about 2.25 Å. Reversible oxidation to 2+ and 2+ proceeds at the ferrocene units, while reduction leads to the neutral radical complexes  and  with the unpaired electron localized on the DML ligand. The occurrence of two voltammetric steps for the one-electron-reduction process is attributed to a two-species equilibrium caused by the hemilabile coordination of DML. Electrochemical and spectroelectrochemical measurements (UV–vis, IR) reveal increased coordination lability of the reduced complexes and their slow fragmentation.