Synthesis and Spectroelectrochemical Studies of Mixed Heteroleptic Chelate Complexes of Ruthenium(II) with 1,8-Bis(2-pyridyl)-3,6-dithiaoctane (pdto) and Substituted 1,10-Phenanthrolines

Abstract

Reaction of dichlorotris(triphenylphosphine) ruthenium(II) [RuCl(2)(PPh(3))(3)] with 1,8-bis(2-pyridyl)-3,6-dithiaoctane (pdto), a (N(2)S(2)) tetradentate donor, yields a new compound [Ru(pdto)(PPh(3))Cl]Cl (1), which has been fully characterized. (1)H and (31)P NMR studies of 1 in acetonitrile at several temperatures show the substitution of both coordinated chloride and triphenylphosphine with two molecules of acetonitrile, as confirmed by the isolation of the complex [Ru(pdto)(CH(3)CN)(2)]Cl(2) (2). Cyclic voltammetric and spectroelectrochemical techniques allowed us to determine the electrochemical behavior of compound 1. The substitution of the chloride and triphenylphosphine by acetonitrile molecules in the Ru(II) coordination sphere of compound 1 was also established by electrochemical studies. The easy substitution of this complex led us to use it as starting material to synthesize the substituted phenanthroline coordination compounds with (pdto) and ruthenium(II), [Ru(pdto)(4,7-diphenyl-1,10-phenanthroline)]Cl(2).4H(2)O (3), [Ru(pdto)(1,10-phenanthroline)]Cl(2).5H(2)O (4), [Ru(pdto)(5,6-dimethyl-1,10-phenanthroline)]Cl(2).5H(2)O (5), [Ru(pdto)(4,7-dimethyl-1,10-phenanthroline)]Cl(2).3H(2)O (6), and [Ru(pdto)(3,4,7,8-tetramethyl-1,10-phenanthroline)]Cl(2).4H(2)O (7). These compounds were fully characterized, and the crystal structure of 4 was obtained. Cyclic voltammetric and spectroelectrochemical techniques allowed us to determine their electrochemical behavior. The electrochemical oxidation processes in these compounds are related to the oxidation of ionic chlorides, and to the reversible transformation from Ru(II) to Ru(III). On the other hand, a single reduction process is associated to the reduction of the substituted phenanthroline in the coordination compound. The E(1/2) (phen/phen(-)) and E(1/2) (Ru(II)/Ru(III)) for the compounds (3-7) were evaluated, and, as expected, the modification of the substituted 1,10-phenanthrolines in the complexes also modifies the redox potentials. Correlations of both electrochemical potentials with pK(a) of the free 1,10-phenathrolines, lambda(max) MLCT transition band, and chemical shifts of phenanthrolines in these complexes were found, possibly as a consequence of the change in the electron density of the Ru(II) and the coordinated phenanthroline.

Synthesis and structures of two ruthenium dibenzoylmethane triphenylphosphine mixed ligand complexes

“…For synthesis of the complexes, solvents were degassed with Ar for 30 min before use. [{RuCl 2 (PPh 3 ) 3 } 2 ] was synthesized following a standard procedure [18].…”

Ruthenium complexes of diphenylphosphino derivatives of carboxylic amides: Synthesis and characterization of bidentate P,N- and P,O-chelate ligands and their reactivity towards [RuCl2(PPh3)3]

“…Following literature methods [24,25], which report the synthesis of [RuCl 2 (PPh 3 ) 3 ] from commercial RuCl 3 ⋅ 3H 2 O, we prepared [RuCl 2 (PPh 3 ) 3 ] from elemental Ruthenium without isolating the intermediate Ru(III)-chloride: A mixture of Ruthenium powder (0.750 g, 7.42 mmol), NaOH (4.00 g, 100 mmol) and NaClO 3 (2.63 g, 24.7 mmol) was cautiously heated in a crucible (using a Bunsen burner) for 15 min (until the evolution of gas from the deep red melt ceased). The mixture was allowed to cool to ambient temperature and was then dissolved in conc.…”

“…Following literature methods [24,25] mmol), NaOH (4.00 g, 100 mmol) and NaClO 3 (2.63 g, 24.7 mmol) was cautiously heated in a crucible (using a Bunsen burner) for 15 min (until the evolution of gas from the deep red melt ceased). The mixture was allowed to cool to ambient temperature and was then dissolved in conc.…”

Ruthenium(II) complexes of some simple classic amine ligands

“…Ru(PPh 3 ) 3 Cl 2 and Ru(Phen)(DMSO) 2 Cl 2 were prepared via literature methods. [11][12][13] Acetonitrile used for electrochemical analysis was distilled off P 4 O 10 under N 2 . UV-Vis spectra were obtained using a Perkin-Elmer Lambda-35 UV-Vis spectrophotometer.…”

“…Oddly, however, some classical coordination compounds of ruthenium with simple multidentate amines appear to be underrepresented in the literature; with tris(2-aminoethyl)amine (Tren), only one Ru(II)-Tren complex [9] and two Ru(III)-Tren [10] complexes having been reported previously (the former during our execution of this work). In this study, and Ru(DMSO) 4 Cl 2 as starting complexes, the first having recently been demonstrated to be a useful synthesis intermediate [11,12] .…”