Utilizing Diruthenium Components for the Design of Cyanide-Linked Tri- and Tetranuclear Organometallic Complexes with Multistep One-Electron Redox Processes

Reactions between the acetate-bridged diruthenium complex Ru2(O2CCH3)4Cl and the
cyanide-containing organometallic complex Cp(dppe)FeCN or Cp(PPh3)2RuCN brought about
the isolation of the cyanide-linked tetranuclear complexes [{Cp(dppe)FeCN}2Ru2(O2CCH3)4](SbF6) (1SbF6) and [{Cp(PPh3)2RuCN}2Ru2(O2CCH3)4](SbF6) (2SbF6), while the similar
reactions of the ap- or Fap-bridged (ap = 2-anilinopyridinate anion, Fap = 2-(2-fluoroanilino)pyridinate anion) diruthenium complex Ru2(ap)4Cl or Ru2(Fap)4Cl with Cp(dppe)FeCN or
Cp(PPh3)2RuCN gave the cyanide-linked trinuclear complexes [Cp(dppe)FeCNRu2(ap)4](SbF6)
(3SbF6), [Cp(PPh3)2RuCNRu2(ap)4](SbF6) (4SbF6), [Cp(dppe)FeCNRu2(Fap)4](SbF6) (5SbF6),
and [Cp(PPh3)2RuCNRu2(Fap)4](SbF6) (6SbF6). The structural analyses indicate that the
steric effect is the predominant factor to govern the nuclearity of the cyanide-linked species.
The steric hindrance derived from (4, 0) (for Ru2(ap)4) or (3, 1) (for Ru2(Fap)4) orientation in
the diruthenium components is extremely unfavorable for the formation of the tetranuclear
arrays MCNRu2(ap)4NCM or MCNRu2(Fap)4NCM (M = Fe or Ru) so as to afford the
trinuclear assembly MCNRu2(ap)4 or MCNRu2(Fap)4 instead. The cyanide-linked complexes
possess rich redox chemistry to afford two or more reversible redox processes. The complexes
were characterized by elemental analysis, IR, UV−vis, 31P NMR, and ES-MS spectroscopy,
and cyclic voltammetry. The crystal structures of 2SbF6−5SbF6 were determined by X-ray
crystallography.