Application of new Ru (II) pyridine‐based complexes in the partial oxidation of n‐ octane

Tridentate and bidentate Ru (II) complexes were prepared through reaction of four pyridine‐based ligands: pyCH 2 N(R)CH 2 py {R = propyl, tert‐ butyl, cyclohexyl and phenyl; py = pyridine} with the [(η 6 ‐C 6 H 6 )Ru(μ‐Cl)Cl] 2 dimer. Crystal structures of the new terdentate Ru (II) complexes [Ru{pyCH 2 N(R)CH 2 py}C 6 H 6 ](PF 6 ) 2 (R = C 3 H 7 ( 1 ), C (CH 3 ) 3 ( 2 ), C 6 H 11 ( 3 ) and the bidentate Ru (II) complex [Ru{pyCH 2 N(R)}C 6 H 6 ]PF 6 (R = C 6 H 5 ( 4 )) are reported. It was found that complexes 1, 2 , 3 and 4 crystallised as mono‐metallic species, with a piano stool geometry around each Ru centre. All complexes were active in the selective oxidation of n ‐octane using t ‐BuOOH and H 2 O 2 as oxidants. Complexes 2 and 4 reached a product yield of 12% with t ‐BuOOH as oxidant, however, superior yields (23–32%) were achieved using H 2 O 2 over all systems. The selectivity was predominantly towards alcohols (particularly 2‐octanol) over all complexes using t ‐BuOOH and H 2 O 2 after reduction of the formed alkylhydroperoxides in solution by PPh 3 . High TONs of up to 2400 were achieved over the Ru/H 2 O 2 systems.