REACTIVITY OF RUTHENIUM COMPLEXES WITH UNINEGATIVE (X,S)-DONOR LIGANDS (X=S,P) .2. PHOSPHINE SUBSTITUTION IN [RU(S,S)2(PR3)2] DERIVATIVES - CRYSTAL-STRUCTURE OF TRANS-BIS(O-ETHYLDITHIOCARBONATE)BIS(DIMETHYLPHENYLPHOSPHINE)-RUTHENIUM(II)

The complexes [Ru(S,S)2(PPh3)2][S,S = EtCOCS2- (CH2)4NCS2-] react with a variety of tertiary phosphines with the substitution of triphenylphosphine and the formation of [Ru(S,S)2(PR3)2]. The reaction occurs with the formation of the cis isomer, except for the complex with PMe2Ph that gives rise to the trans isomer as the crystal structure shows. The effect of the different phosphines on the ruthenium complex is analysed in terms of the spectroscopic and electrochemical properties of the isolated compounds. The cyclic voltammetric studies of the cis complexes show that isomerization to the trans isomer occurs on oxidation. This isomerization is not observed in the trans-[Ru(S,S)2(PMe2Ph)2] complexes that give rise to stable trans-ruthenium(II)/ruthenium(III) couples. In a similar way the diphosphine complexes afford a quasi-reversible cis-ruthenium(II)/ruthenium(III) process.