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

Treatment of the labile (hexamethylbenzene)ruthenium(II) acetone complex [(η 6 -C 6 Me 6 )Ru(OCMe 2 ) 3 ] 2+ with 1,4,7-trithiacyclononane (9S3) gives the half-sandwich salt [(η 6 -C 6 Me 6 )Ru(9S3)](PF 6 ) 2 ( 1 ), which undergoes two successive deprotonations at its methylene carbon atoms in the presence of KOH. The products are chelate vinyl thioether complexes, [(η 6 -C 6 Me 6 )Ru(S(CH CH 2 )CH 2 CH 2 SCH 2 CH 2 S)]PF 6 ( 2 ) (48% isolated yield) and (η 6 -C 6 Me 6 )Ru(S(CH CH 2 )CH 2 CH 2 S)(SCH CH 2 ) ( 3 ) (34% isolated yield); the latter also contains the novel η 1 ( S )-ethenethiolate ligand. Treatment of 1 or 2 with more than 3 molar equiv of KO- t -Bu induces deprotonation of one of the C 6 Me 6 methyl groups; addition of the resulting carbanion to the vinyl group of the coordinated thioether of 3 gives Ru(SCH CH 2 )(S(CH 2 CH 2 CH 2 -η 6 -C 6 Me 5 )CH 2 CH 2 S) ( 4 ) (50% isolated yield), which contains a tridentate arene−thioether−thiolate ligand in addition to η 1 ( S )-ethenethiolate. Complexes 2 − 4 have been characterized by NMR ( 1 H, 13 C) 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 η 2 -thioacetaldehyde, i.e., [(η 6 -C 6 Me 6 )Ru(S(CH CH 2 CH 2 CH 2 S)(η 2 -SCHCH 3 )] + ( 8 ) and [Ru(η 2 -SCHCH 3 )(S(CH 2 CH 2 CH 2 -η 6 -C 6 Me 5 )CH 2 CH 2 S)] + ( 7 ), respectively, which exist as diastereomeric mixtures, as shown by 1 H and 13 C NMR spectroscopy. Complex 8 undergoes a slower, second protonation of the vinyl thioether to give, after C−S bond formation, [(η 6 -C 6 Me 6 )Ru(S(η 2 -CHCH 3 )CH 2 CH 2 SCH 2 CH 2 S)] 2+ ( 9 ).