No abstract

The reaction of the dinuclear [RuCl2(dppb)]2(μ-dppb) (dppb = 1,4-bis(diphenylphosphino)butane) with Cl2 in MeOH for ∼30 min at room temperature gives the bright-red solid mer-RuCl3(dppb)(H2O) (1); Cl2 treatment for ∼10 min affords the red-brown, mixed valence complex [RuCl(dppb)]2(μ-Cl)3 (2). Controlled bulk coulometric reduction of 50% of the content of a CH2Cl2 solution of 1 also produces 2, formed by the reaction of 1 with “RuCl2(dppb)” produced in situ during the electrolysis. Complexes 1 and 2 were characterized by spectroscopic techniques [including electron spin resonance (ESR)], magnetic moments and cyclic voltammetry, and the structure of 1 was determined by X-ray diffraction. The structure shows that the aquo ligand forms hydrogen bonds with two cis-chlorine ligands of the neighboring molecule of the complex; this interaction gives rise to exchange coupling between two Ru(III) centers that is reflected in the ESR spectrum. A species 3 analogous to 1 has been obtained with the diop ligand [diop = (2R,3R)- or (2S,3S)-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane], on using RuCl2(diop)(PPh3) or [RuCl(diop)]2(μ-Cl)3 as precursors. The RuCl3(P-P)L complexes (P-P = dppb, diop; L = dimethyl sulfoxide, MeOH) are readily synthesized from 1 or 3.

Electrolysis has been examined as a method of synthesis for [(L)(dppb)Ru(µ-Cl) 3 RuCl(dppb)] complexes, where dppb = 1,4-bis(diphenylphosphino)butane and L = pyridine (py), 4-methylpyridine (4-pic) or dimethyl sulfoxide (DMSO), by using [RuCl 3 (dppb)(L)] as precursors. The products of the electrolysis were characterized by 31 P-{ 1 H} NMR, cyclic voltammetry and near infrared spectroscopy. The presence of the [Ru 2 Cl 5 (dppb) 2 ] complex in the electrochemical cell suggests a mechanism by which the starting original species from the bulk solution reacts with the reduced form [RuCl 2 (dppb)(L)] generated at the surface of the electrode. The crystal structure of the precursor mer-[RuCl 3 (dppb)(4-pic)] was determined by X-ray diffraction.