Carbon Hydrogen Bond Cleavage Reaction in 5-Coordinate Bis(2,6-dimethylbenzenethiolato)ruthenium(II) Complexes

A series of bis(2,6-dimethylbenzenethiolato)ruthenium(II) complexes, Ru(SC(6)H(3)Me(2)-2,6-kappa(1)S)(2)-(TRIPHOS-kappa(3)P,P',P '') (2a), Ru(SC(6)H(3)Me(2)-2.6-kappa(1)S)(2)(TDPME-K3P,P,PH) (2b), trans-Ru(SC(6)H(3)-BMe-t-2,6-kiS),(DPPE-K(2)P,P')(2) (3c) and Ru(SC(6)H(3)Me-2,6-K(1)S)(2)(PMe(3))(3) (2d) are prepared. Treatment of 2a with PMe(3) in benzene at 50 degrees C results in the sp(3)C-H bond cleavage reaction of the ortho methyl in thiolato group to give a stercochemical mixture of thiaruthenacycle complex Ru[SC(6)H(3)-(CH(2))(Me-6)-kappa(2)S,C](TRIPHOS-kappa(3)P,P',P '')(PMe(3)) (1a) in 70% yield ([(OC-6-34)-1a]/[(OC-6-25)-1a] = 80/20) with concomitant liberation of 2,6-dimethylbenzenethiol. Similar treatment of 2d with PMe(3) in benzene at room temperature rapidly produced cis-Ru[SC(6)H(3)(CH(2)-2)(Me-6)-kappa(2)S, C](PMe(3))(4) (1d) quantitatively. Treatment of 2b with PMe(3) results in the formation of 1d by the C-H bond cleavage reaction and ligand displacement reaction. The C H bond cleavage reaction does not occur from 3c under these conditions. Treatment of 2d with PMe(3) in methanol does not give 1d at all but yields cis-Ru(SC(6)H(3)Me(2)-2,6-kappa(1)S)(2)(PMe(3))(4) (3d), which is not responsible for formation of Id, suggesting importance of coordinative unsaturation for the C-H bond cleavage reaction. The kinetic study suggests that present C-H bond cleavage reaction proceeds by a concerted mechanism.