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

Abstract

Reactions of 3‐(2‐pyridyl)indene and 5‐methyl‐3‐(2‐pyridyl)indene with Ru(PPh3)3Cl2, generated two phosphine‐tethered indenyl ruthenium complexes {η5,κ1P‐(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 {η5‐(CH3C5H3N‐C9H6)}RuCl(PPh3)2 (3); 1 could further react with NaBArF4 to produce a cationic complex [{η5,κ1P‐(C5H4N‐C9H5‐C6H4PPh2)}Ru(PPh3)][BArF4] (15). When treated with NaOMe in methanol, 1 was converted into [{η5,κ1P‐(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 α‐vinylbenzyl alcohol was used as the substrate, requiring catalyst loading of 1 mol%.