The electrosynthesis of Rh2(dpf)4(R) where dpf is the N,N′-diphenylformamidinate anion and R = CH3, C2H5, C3H7, C4H9 or C5H11 was carried out in THF containing 0.2 M tetra-n-butylammonium perchlorate (TBAP) and one of several alkyl iodides represented as RI. The initial step in the reaction involved a one-electron reduction of the Rh24+ unit in Rh2(dpf)4 to its Rh23+ form followed by a homogeneous reaction involving electrogenerated [Rh2(dpf)4]− and the alkyl iodide in solution to give Rh2(dpf)4(R). The homogeneously generated Rh25+ product was then immediately reduced by a second electron at the potential where [Rh2(dpf)4(R)]− is generated, giving [Rh2(dpf)4(R)]− which contains a Rh24+ center as a final product of an electrochemical ECE mechanism. The electrosynthesized [Rh2(dpf)4(CH3)]− derivative could be reoxidized to Rh2(dpf)4(CH3) on the reverse potential sweep and both forms of the CH3 bonded derivative were in situ characterized by cyclic voltammetry combined with UV-visible and/or ESR spectroscopy. The reversible Rh24+/3+ process of Rh2(dpf)4 is located at E1/2 = −1.11 V in THF, 0.2 M TBAP while the electrogenerated Rh2(dpf)4(R) products are substantially easier to reduce, with Ep values for the Rh25+/4+ couples ranging from −0.50 to −0.54 V vs.SCE depending upon the specific R group.
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?