110078-35-8Relevant articles and documents
Directed metal oxidation levels in azo-ruthenium cyclometalates. Synthesis and structure of a trivalent family
Lahiri, Goutam Kumar,Bhattacharya, Samaresh,Mukherjee, Monika,Mukherjee, Alok Kumar,Chakravorty, Animesh
, p. 3359 - 3365 (2008/10/08)
Substituted azobenzenes react with Ru(PPh3)3X2 (X = Cl, Br) to afford complexes (3-6) of type A in which the metal oxidation state is directed by the donor group Y. When Y = O, the metal is trivalent (3, 4, 6), and when Y = OMe, SMe, it is bivalent (Chemical Equation Presented) (5). The Y = O complexes represent the first example of cyclometalated ruthemum(III). The structure of 4b, i.e., A with Y = O, R = Me, R′ = H, and X = Br, RuC49H40N2OP2Br, has been determined by X-ray crystallography. The crystals of 4b are monoclinic in the space group P21/c with Z = 4 and unit cell dimensions a = 12.361 (2) ?, b = 19.091 (3) ?, c = 18.560 (4) ?, β = 108.30 (1)°, and V = 4158.3 (13) ?3. The structure was refined to R = 0.046 and Rw = 0.059. The azo ligand and the bromide are bound in approximately planar C, N, O, Br tetracoordination, and the PPh3 ligands occupy trans positions. The coordination sphere is highly distorted octahedral. The EPR spectra of 4b and other Y = O complexes (low-spin d5) are uniformly rhombic (77 K, frozen solution). The magnitude of axial (Δ) and rhombic (V) distortion parameters and the optical transition energies (v1 and v2) among Kramers doublets are computed to be ～12000, ～9000, ～7000, and ～16000 cm-1, respectively. The v1 transition is experimentally observed at ～8000 cm-1. Results are rationalized in terms of the orbital energy order dxy > dXz > dyz. The redox potentials of the Y = O complexes in dichloromethane lie in the following ranges (vs. SCE): ruthenium-(IV)-ruthenium(III), +1.0 to +0.6 V; ruthenium(III)-ruthenium(II), -0.3 to -0.7 V. In contrast, the Y = OMe, SMe complexes display only the latter couple but at much higher potentials: ～0.7 V (OMe) and ～1.0 V (SMe).
