The electrochemical behavior of binuclear ruthenium(II) complexes of the type [{(arene)RuCl2}(2)] where arene = benzene (1), toluene (2), p-cymene (3) and hexamethyl benzene, (HMB) (4), have been studied by cyclic voltammetry, coulometry and voltammetry with rotating disk and ring-disk electrodes. These compounds undergo electrochemical quasi-reversible reduction in dimethylsulphoxide (DMSO) and acetonitrile (MeCN). The ruthenium(I) species formed react in a very fast chemical reaction (EC mechanisms), although the rate constants of electrochemical and chemical processes are different for the arenes studied. Conditional rate constants (k) and charge transfer coefficients (alpha) for the cathodic reactions were determined by rotating disk techniques, and the kinetic collection efficiency (N-k) was determined with a rotating ring-disk electrode. On the other hand, the binuclear complexes 1 and 2 are quasi-reversibly oxidized in MeCN solution in two electron steps yielding binuclear Ru(III) species, while complex 3 is partially oxidized to give a mixture of products, and complex 4 generates a very unstable species, which chemically returns to the starting reduced complex.

The uncoordinated P atom of the bis(diphenylphosphine)amine (dppa) ligand in complexes [(ring)MCl2(η1-P-PPh2NHPPh2)] (M=Rh, Ir, Ru) reacts with sulphur or selenium to form [(ring)MCl2(η1-P-PPh2NHP(E)Ph2)] (E=S (1–3), Se (4–6)) containing the P-coordinated monosulphide or monoselenide ligands. The selenium derivatives have also been directly prepared from the corresponding [{(ring)MCl2}2] dimer and dppaSe. Chloride abstraction from rhodium and ruthenium complexes gives the neutral compounds [(ring)MCl(η2-P,E-PPh2NP(E)Ph2)] (7–10) whilst the iridium derivatives yield cationic complexes of the general formula [{η5-C5Me5)IrCl(η2-P,E-PPh2NHP(E)Ph2)]+ (11 and 12). The crystal structure of complex [(η5-C5Me5)RhCl{η2-P,Se-PPh2NP(Se)Ph2}] has been established by X-ray crystallography. The rhodium atom exhibits a distorted octahedral coordination with a η5-C5Me5 group occupying the centre of three octahedral sites; a bidentate chelate P,Se-bonded ligand and a chloride atom complete the metal coordination sphere.

La reaccion del complejo dinuclear [{(h6-C6Me6)Ru(µ-Cl)Cl} 2] con el ligando NH(PPh2)2 en relacion molar 1:2 genera el complejo mononuclear [(h6-C6Me6)RuCl 2{h1-(PPh2)2 NH}](1), el que posteriormente reacciona con AgPF6 formando el complejo cationico [(h6-C6Me6)RuCl{h 2-(PPh2)2NH}]PF6 (2). El complejo 2 reacciona con KOBut con formacion del complejo neutro [(h6-C6Me6)RuCl{h 2-(PPh2)2N}](3). El ligando anionico del complejo 3 reacciona facilmente con HBF4 regenerando el complejo de partida y con MeI a traves de la metilacion del atomo de nitrogeno del ligando coordinado. El atomo de fosforo no coordinado del complejo 1 reacciona con azufre o selenio con formacion del ligando coordinado monosustituido,[{(h6-C6 Me6)RuCl2{h1PPh 2NHP(E)Ph2}] (5,6). El tratamiento de los complejos 5 y 6 con AgPF6 conduce a la formacion de compuestos cationicos (7,8) o neutros (9,10) dependiendo del tipo de disolvente utilizado. El atomo de nitrogeno del complejo neutro 9 puede ser derivatizado por reaccion con MeI

Reaction of the complex [{(eta(5)-C5Me5)RhCl2}(2)], in CH2Cl2 solution, with AgBF4 (1:2 molar ratio) and (SPPh2)(3)CH leads to the cationic compound [(eta(5)-C5Me5)RhCl{eta(2)-(SPPh2)(2)CH(SPPh2)-S,S'}]BF4 (1) which is deprotonated by thallium(I) pyrazolate affording [(eta(5)-C5Me5)Rh{eta(3)-(SPPh2)(3)C-S,S',S "}]BF4 (2a). The iridium dimer [{(eta(5)-C5Me5)IrCl2}(2)] reacts with silver salts and (SPPh2)(3)CH, in CH2Cl2 or Me2CO, under analogous conditions, affording mixtures of [(eta(5)-C5Me5)IrCl{eta(2)-(SPPh2)(2)CH(SPPh2)-S,S'}](+) and [(eta(5)-C5Me5)Ir{eta(3)-(SPPh2)(3)C-S,S',S "}]A [A = BF4- (3a), PF6- (3b)]. Addition of Et3N to the mixture gives pure complexes 3. The ruthenium complexes [{(eta(6)-arene)RuCl2}(2)] (arene = C6Me6, p-MeC6H4Pri) react with (SPPh2)(3)CH, in the presence of AgA (A = PF6- or BF4-) or Na BPh4, in CH2Cl2 or Me2CO, yielding only the deprotonated complexes [(eta(6)-arene)Ru{eta(3)-(SPPh2)(3)C-S,S',S "}]A [arene = C6Me6, A = BF4; arene = p-MeC6H4Pri, A = BPh4 (4a), PF6 (4b)]. The crystal structures of 3a and 4a were established by X-ray crystallography. Compound 3a crystallizes in the orthorhombic space group Pna2(1), with lattice parameters a = 41.477(6), b = 10.6778(11), c = 20.162(3) Angstrom and Z = 8. Complex 4a crystallizes in a monoclinic lattice, space group P2(1)/n, with a = 20.810(4), b = 12.555(3), c = 23.008(4) Angstrom, beta = 95.82(2)degrees and Z = 4. Both cationic complexes exhibit analogous pseudo-octahedral molecular structures with the anionic (SPPh2)(3)C- ligand bonded via the three sulphur atoms in a tripodal, tridentate fashion. Each metal centre completes its coordination environment with a eta(5)-C5Me5 (3a) or a eta(6)-MeC6H4Pri group (4a). A quite interesting result concerns the non-planarity of the methanide carbon which display P-C-P angles in the range 112.6-114.4(5)degrees in 3a and 111.9-113.6(4)degrees in 4a. The redox chemistry of the complexes was investigated by cyclic voltammetry. The Rh(III) complexes are quasi-reversibly reduced to Rh(I) and the Ir(III) complex is irreversibly reduced to Ir(I) in acetonitrile solutions. The Ru(II) complex undergoes a quasi-reversible reduction to Ru(I) and a reversible oxidation to Ru(III). (C) 1997 Elsevier Science S.A.