Activation of the Propargylic C−H Bond and Formation of the Unsaturated C3S2 Five-Membered Rings on the RuSSRu Core

The reactions of the disulfide-bridged dinuclear Ru III complex [{Ru(P(OCH 3 ) 3 ) 2 (CH 3 CN) 3 } 2 (μ-S 2 )](CF 3 SO 3 ) 4 ( 1 ) with terminal and internal alkynes gave [{Ru(P(OCH 3 ) 3 ) 2 (CH 3 CN) 3 } 2 (μ-SCR 1 CHCHR 2 S)](CF 3 SO 3 ) 4 ( 2, R 1 = H, R 2 = SC 6 H 5; 3, R 1 = H, R 2 = C 2 H 5; 4, R 1 = CH 3, R 2 = H; 5, R 1 = C 2 H 5, R 2 = CH 3, 6, R 1 = C 6 H 5, R 2 = H), in which an unsaturated C 3 S 2 five-membered ring is formed via activation of the propargylic C−H bond. Treatment of 1 with an unsymmetric alkyne, 2-pentyne, gave a mixture of [{Ru(P(OCH 3 ) 3 ) 2 (CH 3 CN) 3 } 2 (μ-SC(CH 3 ) CHCH(CH 3 )S)](CF 3 SO 3 ) 4 ( 7 ) and [{Ru(P(OCH 3 ) 3 ) 2 (CH 3 CN) 3 } 2 (μ-SC(CH 2 CH 3 ) CHCH 2 S)](CF 3 SO 3 ) 4 ( 8 ), which corresponds to the activation of secondary and primary propargylic C−H bonds, respectively. The reaction at 0 °C preferably gave 7, whereas 8 was obtained as the major component at 40 °C.