78128-62-8Relevant articles and documents
Chemistry of ruthenium. 3. Synthesis, structure, and electron-transfer behavior of trans-dihalobis[(arylazo)oximato]ruthenium(III)
Chakravarty,Chakravorty
, p. 3138 - 3143 (2008/10/08)
New haloruthenium(III) (arylazo)oximates of the type RuX2(HL)(L) are described (X = Cl, Br; HL = RC(=NOH)-N=NAr). The RuX2 moiety has trans configuration (IR data); the hydrogen-bonded organic part LHL acts essentially as a planar tetradentate ligand. In effect the coordination sphere is trans-RuN4X2. The complexes are low spin (t2g5, S = 1/2) and display characteristic EPR spectra in the polycrystalline state at room temperature as well as in frozen benzene. The spectra are sensitive to the nature of R and Ar groups and can be nearly isotropic, axial, or rhombic. The complexes show two LMCT bands near 1000 and 580 nm. They undergo a reversible one-electron transfer at the platinum electrode attributable to the ruthenium(III)-ruthenium(II) couple (cyclic voltammetry and constant potential coulometry). The E°298 of this couple is ～0.4 V vs. SCE in acetonitrile. A bromo complex is easier to reduce than the corresponding chloro complex. The interrelationship of E°298 with LMCT band energy is noted. The green ruthenium(II) species RuX2(HL)(L)- has been generated in solution both electrochemically and chemically (reduction by hydroquinone). It has a characteristic MLCT band near 680 nm. Addition of base (NEt3) deprotonates RuX2(HL)(L) quantitatively to RuX2(L)2- with concomitant loss of the electrochemical response which is fully reestablished on addition of acid (HClO4).
