ROUTES TO RUTHENIUM(II) BROMO(SULFOXIDE) COMPLEXES, INCLUDING THE SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF A NEUTRAL DILITHIUM DIRUTHENIUM(II) COMPLEX CONTAINING TERMINAL AND BRIDGING TETRAMETHYLENE SULFOXIDE LIGANDS

The dimeric Ru(II) complex [Br6(TMSO)2Ru2(mu2-TMSO)2(mu3-TMSO)2Li2(TMSO)2] (1) has been isolated from solutions containing RuCl3.3H3O, LiBr and TMSO (TMSO = tetramethylene sulfoxide, O and S indicating oxygen- and sulfur-bonding, respectively). Crystals of 1 are monoclinic, a = 9.489(3), b = 15.828(3), c = 16.984(3) angstrom, beta = 101.45(2)-degrees, Z = 2, space group P2(1)/n. The structure was solved by the Patterson method and was refined by full-matrix least-squares procedures to R = 0.053 and R(w) = 0.062 for 3087 reflections with I greater-than-or-equal-to 3sigma(I). 1 is remarkable in containing four different types of coordinated TMSO ligands: terminal TMSO at Li, terminal TMSO at Ru, a mu2-type (Ru-S-O-Li) and a previously unreported mu3-type (Ru-S-O(Li)2); the complex contains a central, planar, four-membered Li2O2 ring fused to two six-membered Li-O-S-Ru-S-O rings. A co-product is cis-RuBr2(TMSO)4. A corresponding synthesis using dimethyl sulfoxide gives trans-RuBr2(DMSO)4 in high yield. More definitive assignments are presented for the H-1 NMR spectra of the cis-RUX2(TMSO)4 complexes (X=Cl, Br); these reveal the expected inequivalence of the -SCH2 protons, but in free TMSO an inequivalence of the beta-protons is more evident.