Low oxidation state ruthenium chemistry : IV. The reactions of M(CO)2(PPh3)3 complexes (M = Fe, Ru) and the hydrogenation and isomerization of alkenes catalyzed by RuL(CO)2(PPh3)2 (L = H2, PPh3)☆

Abstract The complexes M(CO) 2 (PPh 3 ) 3 (I, M = Fe; II, M = Ru) readily react with H 2 at room temperature and atmospheric pressure to give cis -M(H) 2 (CO) 2 (PPh 3 ) 2 (III, M = Fe;IV,M = Ru). I reacts with O 2 to give an unstable compound in solution, in a type of reaction known to occur with II which leads to cis -Ru(O 2 )(CO) 2 (PPh 3 ) 2 (V). Even compound IV reacts with O 2 to give V with displacement of H 2 ; this reaction has been shown to be reversible and this is the first case where the displacement of H 2 by O 2 and that of O 2 by H 2 at a metal center has been observed. III and IV are reduced to M(CO) 3 (PPh 3 ) 2 by CO with displacement of H 2 ; Ru(CO) 3 - (PPh 3 ) 2 is also formed by treatment of IV with CO 2 , but under higher pressure. Compounds II and IV react with CH 2 CHCN to give Ru(CH 2 CHCN)(CO) 2 - (PPh 3 ) 2 (VI) which reacts with H 2 to reform the hydride IV. cis -Ru(H) 2 (CO) 2 (PPh 3 ) 2 (IV) has been studied as catalyst in the hydrogenation and isomerization of a series of monoenes and dienes. The catalysts are poisoned by the presence of free triphenylphosphine. On the other hand the ready exchange of H 2 and O 2 on the “Ru(CO) 2 (PPh 3 ) 2 ” moiety makes IV a catalyst not irreversibly poisoned by the presence of air. It has been found that even Ru(CO) 2 (PPh 3 ) 3 (II) acts as a catalyst for the isomerization of hex-1-ene at room temperature under an inert atmosphere.