Activation of carbon–sulfur and carbon–chlorine bonds by the electrophilic ruthenium fragment ‘Ru(η-C5Me5)+’

Abstract

The ‘Ru(η-C5Me5)+’ fragment generated by protonation of [{Ru(η-C5Me5)(OMe)}2] by CF3SO3H, reacted with cyclohexene sulfide to give [Ru(η-C5Me5)(η6-C6H6)]+1 and H2S. With 1,4-dithiane no C–S bond activation was observed but instead the successive formation of [Ru(η-C5Me5)(S2C4H8)(CF3SO3)]2 and [Ru(S2C4H8)3]2+3, whereas with 1,3-dithiane two compounds resulting from the sequential activation of C–S bonds were isolated as CF3SO3– salts, namely [{Ru(η-C5Me5)(SMe)(SCH2CHCH2)}2]2+4 and [{Ru[C5Me4CH2S(CH2)3SMe]}2]2+5. The fragment also reacted with neat dichloromethane to give two trinuclear clusters: [{Ru(η-C5Me5)}3(µ-Cl)3(µ3-CH)]+6 and [{Ru(C5Me5)}3(µ-Cl)2(µ-CO)(µ3-CH)]2+7 in 60 and 30% yield respectively. Its reaction with chlorocyclohexane, 1,2-dichlorocyclohexane and 1,2,3,4,5,6-hexachlorocyclohexane (lindane) yielded 1 and various amounts of H2 and HCl. In the case of lindane the conversion was only 30% and yielded a 9:1 mixture of 1 and [Ru(η-C5Me5)(η6-C6H5Cl)]+9. Finally the reaction of C–Cl versus C–O bond activation was compared using 2-chlorocyclohexanone, 2-chlorocyclohexanol and 2,2,6,6-tetrachlorocyclohexanol. It was found that in all cases the C–Cl activation was easier. The first reaction yielded 1, the second the new trinuclear cluster [{Ru(C5Me5)}3(µ-Cl)2(µ-CO)(µ3-CCl)]2+11 similar to 7. The latter reaction depended upon the reaction conditions, but in tetrahydrofuran at 80 °C, an 80% conversion was observed yielding a 1:7: < 1 mixture of 1, [Ru(η-C5Me5)(η6-C6H5OH)]+10 and [Ru(η-C5Me5)(η6-C6H5Cl)]+9 thus demonstrating a high selectivity for C–Cl activation in the presence of C–O bonds.