Preparation, Characterization, Redox Properties, and UV−Vis−NIR Spectra of Binuclear Ruthenium Complexes [{(Phtpy)(PPh₃)₂Ru}₂{C⋮C−(CHCH)<i>_m</i>−C⋮C}]<i>ⁿ</i>⁺ (Phtpy = 4‘-phenyl-2,2‘:6‘,2‘ ‘-terpyridine)

Abstract

A series of C 4 −C 10 bridged Ru 2 II,II complexes [{(Phtpy)(PPh 3 ) 2 Ru} 2 (C⋮C−(CH CH) m −C⋮C)] 2+ ( m = 0, 1, 2, 3) were prepared by reaction of [(Phtpy)(PPh 3 ) 2 Ru(acetone)] 2+ with Me 3 Si−C⋮C−(CH CH) m −C⋮C−SiMe 3 in the presence of potassium fluoride. Oxidation of the Ru 2 II,II complexes by 1 equiv of ferrocenium hexafluorophosphate gave the stable Ru 2 II,III mixed-valence complexes [{(Phtpy)(PPh 3 ) 2 Ru} 2 (C⋮C−(CH CH) m −C⋮C)] 3+ when m = 0, 1, or 2. These complexes were all characterized by microanalyses, ESI-MS, 1 H and 31 P NMR, IR, and UV−vis−NIR spectroscopy, cyclic and differential pulse voltammetry, and X-ray crystallography for compound [ 1 ](PF 6 ) 2 . The wave separations Δ E 1/2 ( E 1/2 A − E 1/2 B ) due to stepwise oxidation of two Ru II into Ru III are 0.610, 0.260, 0.165, and <0.070 V for m = 0−3, respectively, in dichloromethane solutions, revealing a significant dependence of the electronic communication on metal−metal distances. The visible−NIR spectral studies on the Ru 2 II,III mixed-valence complexes [{(Phtpy)(PPh 3 ) 2 Ru} 2 (C⋮C−(CH CH) m −C⋮C)] 3+ ( m = 0, 1, 2) demonstrated that electronic delocalization along the molecular rods attenuates dramatically with the increase of the ethenyl number.