Synthesis, structure and electrochemical properties of 3,4,5-triaryl-1,2-diphosphaferrocenes

Abstract

Aryl-substituted sodium 1,2-diphosphacyclopentadienides Na(P₂C₃R₃) (R = Ph, 4-Me-C₆H₄, 4-Cl-C₆H₄)(1a-c) react with [FeCp(η⁶-C₆H₅CH₃)][PF₆] to give heteroleptic 3,4,5-triaryl-1,2-diphosphaferrocenes [FeCp(η⁵-P₂C₃R₃)] (2a-c) in 71–78% yield. The structures of 2a-c were confirmed by NMR, UV-Vis spectroscopy and X-ray structure analysis, and supported by DFT calculations. Electrochemical studies of 2a-c in CH₃CN demonstrate a pronounced reversible one-electron oxidation, while in the solid state, all 3,4,5-triaryl-1,2-diphosphaferrocenes show fully reversible oxidation and reduction waves, which indicates the stability of the oxidized form. Regardless of the substituent (R = Ph, 4-Me-C₆H₄, 4-Cl-C₆H₄), the studied 1,2-diphosphaferrocenes have similar oxidation and reduction potentials.