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(PPh 3 ) 3 Cl 2 , generated two phosphine‐tethered indenyl ruthenium complexes { η 5 , κ 1 P ‐(C 5 H 4 N‐C 9 H 4 R‐C 6 H 4 PPh 2 )}RuCl(PPh 3 ) (R = H, 1 ; R = CH 3 , 2 ), respectively. While treatment of 3‐(6‐methyl‐2‐pyridyl)indene with Ru(PPh 3 ) 3 Cl 2 gave a product { η 5 ‐(CH 3 C 5 H 3 N‐C 9 H 6 )}RuCl(PPh 3 ) 2 ( 3 ); 1 could further react with NaBAr F 4 to produce a cationic complex [{ η 5 , κ 1 P ‐(C 5 H 4 N‐C 9 H 5 ‐C 6 H 4 PPh 2 )}Ru(PPh 3 )][BAr F 4 ] ( 15 ). When treated with NaOMe in methanol, 1 was converted into [{ η 5 , κ 1 P ‐(C 5 H 4 N‐C 9 H 5 ‐C 6 H 4 PPh 2 )}RuH(PPh 3 )] ( 16 ). These five complexes were investigated as catalysts for redox isomerization of allylic alcohols, and 16 exhibited best catalytic activity in the presence of t BuOK, reaching quantitative yield in 5 min when α‐vinylbenzyl alcohol was used as the substrate, requiring catalyst loading of 1 mol%.