Studies on some mixed-ligand complexes of ruthenium(II) involving dithiocarboxylates, dithiocarbamates, triphenylphosphine and bipyridine

Abstract

Ruthenium(II) complexes [Ru(R-acda) 2(PPh 3) 2] ( 1a–e), [Ru(R-acda)(bpy) 2](ClO 4)( 2a–d), [Ru(R-acda)(phen) 2](ClO 4) ( 2e–g), [Ru(R 2-dtc)(bpy) 2](ClO 4)( 3a,b) and [Ru(R 2-dtc) (phen) 2](ClO 4)( 3c,d), (where R-acdaH = 2-alkylamino-1-cyclopentene-1-dithicarboxylic acid, R 2-dtcNa = sodium N, N′-dialkyl dithiocarbamate, bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline) have been synthesized and characterized. The 1H NMR spectra of the phosphine complexes ( 1a–e) show that, with the increase in the chain length of the alkyl group of R-acda −, the N-alkylamino proton becomes more deshielded and is accompanied by a shift of the NH stretching frequency ν(NH) to lower energy. A linear relationship is obtained between the chemical shift δ(NH) and ν(NH). All the complexes exhibit absorption bands due to dπ → π ∗ (bpy, phen or PPh 3), dπ → π ∗ (R-acda − or R 2-dtc −) charge transfer transitions and π → π ∗ intraligand transition. Complexes 1a–e undergo two irreversible oxidations, Ru II → Ru III and Ru III → Ru IV , while the other complexes ( 2,3) exhibit one reversible (Ru II/Ru III) and one irreversible (Ru III → Ru IV ) oxidation process.