Base-Induced Fragmentation of a Macrocyclic Thioether at an (Arene)ruthenium(II) Center. Generation of η¹(<i>S</i>)-Ethenethiolate and η²(<i>C</i>,<i>S</i>)-Thioacetaldehyde

Treatment of the labile (hexamethylbenzene)ruthenium(II) acetone complex [(η6-C6Me6)Ru(OCMe2)3]2+ with 1,4,7-trithiacyclononane (9S3) gives the half-sandwich salt [(η6-C6Me6)Ru(9S3)](PF6)2 (1), which undergoes two successive deprotonations at its methylene carbon atoms in the presence of KOH. The products are chelate vinyl thioether complexes, [(η6-C6Me6)Ru(S(CHCH2)CH2CH2SCH2CH2S)]PF6 (2) (48% isolated yield) and (η6-C6Me6)Ru(S(CHCH2)CH2CH2S)(SCHCH2) (3) (34% isolated yield); the latter also contains the novel η1(S)-ethenethiolate ligand. Treatment of 1 or 2 with more than 3 molar equiv of KO-t-Bu induces deprotonation of one of the C6Me6 methyl groups; addition of the resulting carbanion to the vinyl group of the coordinated thioether of 3 gives Ru(SCHCH2)(S(CH2CH2CH2-η6-C6Me5)CH2CH2S) (4) (50% isolated yield), which contains a tridentate arene−thioether−thiolate ligand in addition to η1(S)-ethenethiolate. Complexes 2−4 have been characterized by NMR (1H, 13C) and IR spectroscopy and by single-crystal X-ray structural analysis. Whereas 2 is reconverted into 1 by acid, in the case of 3 and 4 the ethenethiolate groups are protonated to generate cationic complexes containing η2-thioacetaldehyde, i.e., [(η6-C6Me6)Ru(S(CHCH2CH2CH2S)(η2-SCHCH3)]+ (8) and [Ru(η2-SCHCH3)(S(CH2CH2CH2-η6-C6Me5)CH2CH2S)]+ (7), respectively, which exist as diastereomeric mixtures, as shown by 1H and 13C NMR spectroscopy. Complex 8 undergoes a slower, second protonation of the vinyl thioether to give, after C−S bond formation, [(η6-C6Me6)Ru(S(η2-CHCH3)CH2CH2SCH2CH2S)]2+ (9).