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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