Synthesis, structures, and properties of ruthenium(II) complexes of N-(1,10-phenanthrolin-2-yl)imidazolylidenes

Mononuclear ruthenium complexes RuCl(L1)(CH(3)CN)(2)](PF(6)) (2a), RuCl(L2)(CH(3)CN)(2)](PF(6)) (2b), Ru(L1)(CH(3)CN)(3)](PF(6))(2) (4a), Ru(L2)(CH(3)CN)(3)](PF(6))(2) (4b), Ru(L2)(2)](PF(6))(2) (5), RuCl(L1)(CH(3)CN)(PPh(3))](PF(6)) (6), RuCl(L1)(CO)(2)](PF(6)) (7), and RuCl(L1)(CO)(PPh(3))](PF(6)) (8), and a tetranuclear complex Ru(2)Ag(2)Cl(2)(L1)(2)(CH(3)CN)(6)](PF(6))(4) (3) containing 3-(1,10-phenanthrolin-2-yl)-1-(pyridin-2-ylmethyl)imidazolylidene (L1) and 3-butyl-1-(1,10-phenanthrolin-2-yl)imidazolylidene (L2) have been prepared and fully characterized by NMR, ESI-MS, UV-vis spectroscopy, and X-ray crystallography. Both L1 and L2 act as pincer NNC donors coordinated to ruthenium (II) ion. In 3, the Ru(II) and Ag(I) ions are linked by two bridging Cl(-) through a rhomboid Ag(2)Cl(2) ring with two Ru(II) extending to above and down the plane. Complexes 2-8 show absorption maximum over the 354-428 nm blueshifted compared to Ru(bpy)(3)(2+) due to strong σ-donating and weak π-acceptor properties of NHC ligands. Electrochemical studies show Ru(II)/Ru(III) couples over 0.578-1.274 V.