Synthesis, characterization, and electrochemistry of dicyclopentadienylsiloxane-bridged dicarbonyldi-iron

Abstract

The new metal–metal bonded binuclear iron complexes [{Fe(CO)₂}₂{η⁵:η⁵′-C₅H₄(RR′SiO)_nSiRR′C₅H₄}][R = R′= Me, n= 1 (1) or 2 (2); R = Me, R′= Ph, n= 1 (3)] have been prepared in good yield by reaction between dicyclopentadienylsiloxanes, C₅H₅(RR′SiO)_nSiRR′C₅H₅(R = R′= Me, n= 1 or 2; R = Me, R′= Ph, n= 1), and [Fe(CO)₅]. Oxidation of (1)–(3) with [Fe(η⁵-C₅H₅)₂]PF₆ in the presence of PPh₃ gives the dicationic complexes [{Fe(CO)₂(PPh₃)}₂{η⁵:η⁵′-C₅H₄(RR′SiO)_nSiRR′C₅H₄}][PF₆]₂[R = R′= Me, n= 1 (7) or 2 (8); R = Me, R′= Ph,n= 1 (9)]. The dianionic complexes K₂[{Fe(CO)₂}₂{η⁵:η⁵′-C₅H₄(RR′SiO)_nSiRR′C₅H₄}][R = R′= Me, n= 1 (10) or 2 (11); R = Me, R′= Ph, n= 1 (12)] were obtained by treating (1)–(3) with potassium diphenylketyl. The new binuclear iron complexes have been characterized by ¹H and ¹³C n.m.r. and i.r. spectroscopy. The electrochemistry of compounds (1)–(3) indicates that two-electron oxidation products are stable on the voltammetric time-scale. Their kinetic stability depends upon the solvent donicity. The final products are dication complexes which do not contain carbonyl bridges (4)–(6).