Base-induced fragmentation of a macrocyclic thioether at an (arene)ruthenium(II) center. Generation of η1(S)-ethenethiolate and η2(C,S)-thioacetaldehyde

Abstract

Treatment of liable (hexamethylbenzene)ruthenium(II) acetone complex [(η6-C6Me6)Ru(OCMMe2)3]2+ with 1,4,7-trithiacyclononane (9S3) gives the half-sandwhich 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 (2) (48% isolated yield) and (34% isolated yield); later 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 (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. (8) and (7), respectively which exist as diastereomeric mixtures, as shown by 1H ad 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)CH2CH2SCH2 CH2S)]+ (9).