Synthesis, structure and chemistry of dinuclear and trinuclear hexamethylbenzene ruthenium acyl thiolate compounds

•(HMB)Ru acyl thiolate isomers (anti and syn) afford specific conformational products.•Dinuclear and trinuclear (HMB)Ru (acyl thiolate) derivatives were synthesized.•Structural results show S bridging acyl thiolate ligands favor the high nuclearity.•Di- and trinuclear acyl thiolate complexes go to a thermodynamic sink product

The compounds [(HMB)Ru(η5-2,5-Me2T)][X]2 [(HMB = η6-hexamethylbenzene), (2,5-Me2T = 2,5-dimethylthiophene), X = BF4,4[BF4]2; OTf, 4[OTf]2 (Rauchfuss, 1992)] react via base hydrolysis, with aqueous KOH, to give two acyl thiolate isomers [(HMB)Ru(η4-SC(Me)CHCHC(O)Me)] (5anti and 5syn). In acidic media 5anti undergoes total reformation to 4[X]2 (X = BF4, OTf), while 5syn behaves differently. Reaction of [(HMB)Ru(acetone)3][BF4]2 (2[BF4]2) or [(HMB)Ru(OTf)2]n (3) with 5syn at room temperature affords the dinuclear ruthenacycles [(HMBRu)2(μ-κ1-S-η3,1-SC(Me)CHCC(O)Me)][X] (X = BF4, 6[BF4]; OTf, 6[OTf]) containing a metal–metal bond, by intramolecular activation of the acyl thiolate C–H bond, whereas the reaction of 2[BF4]2 with 5anti gives the dicationic dinuclear complex [(HMBRu)2(H2O)(κ1,1-S,O-μ-κ1-S-η3-SC(Me)CHCHC(O)Me)][BF4]2 (7[BF4]2). The reaction between both isomers 5anti and 5syn with 2[BF4]2 or 3, at low temperature, produces the trinuclear [{(HMB)Ru(μ-κ1-S-syn-η3-SC(Me)CHCHC(O)Me)}{(HMBRu)2(κ1,1-S,O-μ-κ1-S-η3-SC(Me)CHCHC(O)Me)}][X]2 (X = BF4, 8[BF4]2; OTf, 8[OTf]2), which after heating in CDCl3 at 50 °C lead to cleavage of Ru–S bond of the 5syn moiety to give compound 5syn, along with small amounts of monocationic dinuclear [(HMBRu)2Cl(κ1,1-S,O-μ-κ1-S-η3-SC(Me)CHCHC(O)Me)][X] (X = BF4, 9[BF4]; OTf, 9[OTf]). The full characterization was done by 1H, 13C{1H} NMR and IR spectroscopy, as well as mass spectra and chemical analysis. Compounds 6[OTf], 7[BF4]2, 8[BF4]2 and 9[BF4] have also been further characterized by X-ray diffraction studies.

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