Synthesis and Electrochemical Studies of Ruthenium(II) Dicarbonyl Bis(ferrocenyl‐β‐diketonates)

The reaction of [Ru 3 (CO) 12 ] ( 1 ) with six equiv. of FcC(O)CH 2 C(O)R ( 2a , R = Me; 2b , R = Fc; Fc = Fe(η 5 ‐C 5 H 4 )(η 5 ‐C 5 H 5 )) produced the Ru II compounds [Ru(CO) 2 (FcC(O)CHC(O)R) 2 ] ( 3a , R = Me; 3b , R = Fc) in moderate yields. IR studies and single‐crystal X‐ray analysis ( 3a ) confirmed that the CO ligands are cis ‐oriented and that the respective β‐diketonates O,O '‐chelate‐bonded setting‐up an octahedral surrounding at Ru II . Electrochemical (cyclic and square‐wave voltammetry) and spectroelectrochemical (UV/Vis‐NIR, IR) measurements were additionally carried out. Compounds 3a , b display two ( 3a : E 1 o ' = 140; E 2 o ' = 255 mV; Δ E o ' = 115 mV for [ 3a ] + /[ 3a ] 2+ ) or four ( 3b : E 1 o ' = 80 mV, E 2 o ' 190 mV (Δ E o ' = 110 mV, [ 3b ] + /[ 3b ] 2+ ), E 3 o ' = 355 mV (Δ E o ' = 165 mV, [ 3b ] 2+ /[ 3b ] 3+ ), E 4 o ' = 490 mV (Δ E o ' = 135 mV, [ 3b ] 3+ /[ 3b ] 4+ )) electrochemical reversible one‐electron redox processes indicating electrostatic interactions among the ferrocenyl groups as oxidation progresses, which was confirmed by UV/Vis‐NIR and in situ IR spectroscopy. One ferrocenyl group on each β‐diketonate ligand is by this means 1 st oxidized before the 2 nd ferrocenyl group of the same β‐diketonate building block follows.