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

Aryl-substituted sodium 1,2-diphosphacyclopentadienides Na(P 2 C 3 R 3 ) (R = Ph, 4-Me-C 6 H 4 , 4-Cl-C 6 H 4 )( 1a-c ) react with [FeCp(η 6 -C 6 H 5 CH 3 )][PF 6 ] to give heteroleptic 3,4,5-triaryl-1,2-diphosphaferrocenes [FeCp(η 5 -P 2 C 3 R 3 )] ( 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 CH 3 CN 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-C 6 H 4 , 4-Cl-C 6 H 4 ), the studied 1,2-diphosphaferrocenes have similar oxidation and reduction potentials. New 3,4,5-triaryl-1,2-diphosphaferrocenes [FeCp(η 5 -P 2 C 3 R 3 )] have been extensively studied experimentally (NMR, UV-Vis, electrochemical studies, X-ray) and quantum chemically.