TRANSITION-METAL COMPLEXES WITH SULFUR LIGANDS - 130 - SYNTHESIS, STRUCTURE, AND REACTIVITY OF THE SULFUR-RICH RUTHENIUM HYDRIDE COMPLEXES [RU(H)(PR3)(S-4)(-) AND THE ETA(2)-H-2 COMPLEX [RU(H-2)(PCY3)(S-4)] (R= PH, PR-I, CY S-4(2-) = 1,2-BIS((2-MERCAPTOPHENYL)THIO)ETHANE(2-))

Hydride and eta(2)-H-2 ruthenium complexes with sulfur-rich coordinati on spheres were synthesized. Substitution of either DMSO or PPh3 in [R u(DMSO)(PR3)('S-4')] and [Ru(PPh3)(2)('S-4')] by hydride anions from L iAlH4 or NaBEt3H yielded [Ru(H)(PR3)('S4('))](-) complexes (R = Pr-i, Ph, Cy; 'S-4'(2-) = 1,2-bis((2-mercaptophenyl)thio)ethane(2-)). They w ere isolated as [Li(THF)(Et2O)][Ru(H)(PR3)('S-4')] (R = Pr-i (1a), Cy (1b), Na[Ru(H)(PCy3)('S-4')]. 2BEt(3). 0.5DMSO (2a), and the solvent-f ree Na[Ru(H)(PPh3)('S-4')]. 2BEt(3) (2b). X-ray structure determinatio ns of 1a . 0.5Et(2)O and 1b . Et2O showed that in both complexes pseud aoctahedral [Ru(H)(PR3)('S-4')]- anions an bridged to pseudotetrahedra l [Li(THF)(Et2O)] cations via the hydride Ligand and one thiolate dono r of the 'S-4'(2-) ligand (crystal data: 1a, monoclinic, P2(1)/n, a = 1401.6(2) pm, b = 1045.2(3) pm, c = 2590.6(4) pm, beta = 95.04(1)degre es, V = 3.780(1) nm(3), Z = 4; 1b, triclinic, P (1) over bar, a = 1264 .2(1) pm, b = 1322.9(3) pm, c = 1569.5(2) pm, alpha = 88.96(1)degrees, beta = 83.48(1)degrees, gamma = 62.16(1)degrees, V = 2.3042(6) nm(3), Z = 2). Short intramolecular C-H ... H-Ru contacts (approximate to 23 0 pm) between the hydride ligands, phosphine substituents, and lithium -coordinated Et2O molecules indicate ''unconventional'' hydrogen bonds . They potentially help to decrease the hydridic character of the hydr ide ligand to such an extent that no structural hydride trans influenc e can be observed in the solid stare. In solution at room temperature, all hydride complexes 1a-2b rapidly release H-2 or HD, when treated w ith CH3OH or CD3OD. Low-temperature H-1 and H-2 NMR spectroscopy betwe en -20 and -80 degrees C showed that initially eta(2)-H-2 or eta(2)-HD complexes form. Their formation explains the observed scrambling betw een protons and hydride ligands, which requires a heterolytic cleavage of dihydrogen. A 1:1:1 tripler at delta = -6.5 ppm ((1)J(HD) = 32 Hz, (2)J(PH) = 5 Hz) and a relaxation time of T-1(min) = 4 ms (-60 degree s C, 270 MHz) firmly established the formation of the eta(2)-dihydroge n complexes. The reversibility of H-2 release and uptake by [Ru(PCy3)( 'S4')1 fragments and the heterolytic cleavage of H-2 in [Ru(eta(2)-H-2 )(PCy3)('S-4')] was further ascertained by the reaction of [Ru(DMSO)(P Cy3)('S-4')] with Ha in the presence of NaOMe, yielding the [Ru(H)(PCy 3)('S-4')](-) anion. The relevance of the complexes and their reaction s for the heterolytic H-2 activation at the transition metal sulfur si tes of hydrogenases is discussed.