Synthesis and reactivity of new complexes containing the [Ru(''S-4'')] fragment [''S-4''(2-)=1,2-bis(2-mercaptophenylthio)ethane(2-)]

In order to synthesize labile and well-soluble [Ru(L)(L')(''S-4'')] complexes, [Ru(Cl)(2)(DMSO)(4)] was treated with ''S-4''-Na-2 [''S-4''(2-)=1,2-bis(2-mercaptophenylthio)-ethane(2-)] yielding [Ru(DMSO)(2)(''S-4'')] (1) which contains two labile DMSO ligands. An X-ray structural analysis of 1 verifies that both DMSO ligands are coordinated via their S atoms. The reaction of 1 with small ligands such as PR3 (R=Et, nPr, nBu) or tetrahydrothiophene (THT) leads to substitution of both DMSO ligands yielding [Ru(PR3)(2)(''S-4'')] (R=Et 3a, nPr 3b, nBu 3c) and [Ru(THT)(2)(''S-4'')] 2, respectively, while bulky phosphane ligands such as PCy3 and PiPr(3) substitute one DMSO ligand to yield [Ru(DMSO)(PR3])(''S-4'')] (R=iPr 4a, Cy 4b). X-ray structural analyses of [Ru(PnPr(3))(2)(''S-4'')]. 0.5 MeOH (3b . 0.5 MeOH), [Ru(Pn-Bu-3)(2)(''S-4'')] (3C), and [Ru(PMe3)(2)(''S-4'')] (3d) confirm the pseudo-octahedral coordination of the Ru centers by four S-donors and two cis P-donors and reveal close similarities between the three complexes. Comparison of the structural parameters of 3b . 0.5 MeOH, 3c and 3d with those of [Ru(PPh3)(2)(''MeS4'')][''MeS4''(2-)=1,2-bis(2-mercaptophenyl-thio)propane(2-)] indicates that the inertness towards substitution of 3b . 0.5 MeOH, 3c and 3d as opposed to the substitution lability of [Ru(PPh3)(2)(,MeS4'')] is caused by the small cone angles of the alkyl phosphanes. In the DMSO/PCy3 complex 4b both coligands are labile, and which one is substituted depends on the size of the entering Ligand. The reactions of 4b with PnR(3) yield [Ru(DMSO)(PR3)(''S-4'')] (R=nPr 4c, nBu 4d) in contrast to the reaction with CO, PMe3, and SMe2 which give [Ru(CO)(PCy3)(''S-4'')] (5b), [Ru(PMe3)(PCy3)(''S-4'')] (6), and [Ru(SMe2)(PCy3)(''S-4'')] (7), respectively. In an analogous manner, the CO complexes [Ru(CO)(PR3)(''S-4'')] (R=iPr 5a, nBu 5c) have been obtained by treatment of 4a and 4d with CO. The reactions of 4a and 4b with S-8 yielded the readily soluble mu-S-2 complexes [mu-{Ru(PR3)(''S-4'')}(2)] (R=iPr 8a, Cy 8b). The spectroscopic data of complex 8b and its cyclic voltammogram, which exhibits four quasi-reversible redox waves, indicate a strong elec tronic coupling of the two [Ru(PCy3)(''S-4'')] fragments via the mu-S-2 bridge.