Synthesis of phosphine-tethered indenyl ruthenium complexes through c-h bonds activation followed by C-C bond coupling: High performance catalysts for the redox isomerization of allylic alcohols

Reactions of 3-(2-pyridyl)indene and 5-methyl-3-(2-pyridyl)indene with Ru(PPh3)3Cl2, generated two phosphine-tethered indenyl ruthenium complexes {eta 5,kappa 1P-(C5H4N-C9H4R-C6H4PPh2)}RuCl(PPh3) (R = H, 1; R = CH3, 2), respectively. While treatment of 3-(6-methyl-2-pyridyl)indene with Ru(PPh3)3Cl2 gave a product {eta 5-(CH3C5H3N-C9H6)}RuCl(PPh3)2 (3); 1 could further react with NaBArF4 to produce a cationic complex [{eta 5,kappa 1P-(C5H4N-C9H5-C6H4PPh2)}Ru(PPh3)][BArF4] (15). When treated with NaOMe in methanol, 1 was converted into [{eta 5,kappa 1P-(C5H4N-C9H5-C6H4PPh2)}RuH(PPh3)] (16). These five complexes were investigated as catalysts for redox isomerization of allylic alcohols, and 16 exhibited best catalytic activity in the presence of tBuOK, reaching quantitative yield in 5 min when alpha-vinylbenzyl alcohol was used as the substrate, requiring catalyst loading of 1 mol%. In this paper, we studied the reactions of Ru(PPh3)3Cl2 with 3-(2-pyridyl)indene and its derivatives, generating two phosphine-tethered indenyl ruthenium complexes {eta 5,kappa 1P-(C5H4N-C9H4R-C6H4PPh2)}RuCl(PPh3) (R = H, 1; R = CH3, 2) and an eta 5-coordination mode complex {eta 5-(CH3C5H3N-C9H6)}RuCl(PPh3)2 (3). Complexes 1 and 2 are formed via C-C coupling of the 2-position of the indenyl ring with the ortho-position of a phenyl ring from triphenylphosphine, which is rare in organometallic chemistry. image