Influence of Changing the Remote Substituents on Charge Transfer Properties of Cyanide‐Bridged Trinuclear Fe−Ru−Fe Complexes

Abstract

To investigate the effect of ligand remote (>10 Å) substituents on the bridging metal center on the metal‐to‐metal charge transfer (MMCT) properties in cyanidometa‐bridged complexes, a series of new cyanidometal‐bridged complexes and their one‐electron and two‐electron oxidation products have been synthesized and well characterized (namely, trans‐[Cp(dppe)Fe−NC−(L)Ru(PPh3)−CN−Fe(dppe)Cp][PF6]n (n=2, 3, 4) (L=dmptpy, 1[PF6]n; L=meoptpy, 2[PF6]n; L=t‐Buptpy, 3[PF6]n) (Cp=1,3‐cyclopentadiene, dppe=1,2‐bis(diphenylphosphino)ethane, PPh3=triphenylphosphine, dmptpy=4′‐(4‐dimethylaminophenyl)‐2,2′,6′,2′′‐terpyridine, meoptpy=4′‐(4‐methoxyphenyl)‐2,2′,6′,2′′‐terpyridine, t‐Buptpy=4′‐(4‐tertbutylphenyl)‐2,2′,6′,2′′‐terpyridine)). The investigations suggest that the cyanido‐stretching (νCN) vibration energy for the complexes is unsensitive to the electron‐donating ability change of the remote substituents of the cyanidometal bridging auxiliary ligand from tertbutyl, methoxy to dimethylamino group. However, the MMCT energies of the one‐ and two‐electron oxidation complexes are still sensitive to the remote substituents of the ligand on the bridging metal center, and decreases with the increase of the electron‐donating ability of the remote substituents from tertbutyl, methoxy to dimethylamino group. All one‐electron and two‐electron oxidation products belong to Class II mixed valence compounds according to the classification of Robin and Day.