Generation of 17-electron organometallic radicals in aqueous solution; chemical and electrochemical oxidation of Fe(CO)3(TPPTS)2

The water-soluble iron–carbonyl complex Fe(CO)3(TPPTS)2 (2) (TPPTS=triphenylphosphine trisulfonate, sodium salt) was prepared and its molecular structure was determined by X-ray crystallography to be distorted bipyramidal. The oxidation chemistry of 2 to the 17-electron organometallic radical 2+ was studied. Thus, complex 2 was oxidized chemically with Ce(IV) in H2O, resulting in rapid disproportionation of the intermediate 2+ to 2 and Fe(II)aq, with concomitant loss of both the CO and the TPPTS ligands. The oxidative disproportionation of 2 with AgNO3 proceeded through formation of a linear [{(TPPTS)2(CO)3Fe}2Ag]+ intermediate. Electrochemically, complex 2 was oxidized irreversibly at Ep=466 mV (vs. Ag ∣ AgCl, 100 mV s−1) in H2O.