Bimetallic Ru(II) Complex Catalysed β‐Alkylation of Secondary Alcohols and α‐Alkylation of Ketones: Selective Formation of Saturated Ketones

Ru(II) bimetallic [(p-cymene)2(RuCl)2L1]2X (X = BF4 (Cat2); X = PF6 (Cat3)) and monometallic [(p-cymene)(RuCl)L2]BF4 (Cat4) (where L1 = N,N'-(3,3',5,5'-tetraisopropyl-[1,1'-biphenyl]-4,4'-diyl)bis(1-(pyridin-2-yl)methanimine); L2 = N-(2,6-diisopropyl-phenyl)-1-(pyridin-2-yl)-methanimine) catalyse selective synthesis of saturated ketones using β-alkylation of secondary alcohol or α-alkylation of ketones with primary alcohol. Notably, a single catalyst facilitates the oxidation of both secondary and primary alcohols followed by condensation and hydrogenation yielding α-alkylated saturated ketones. Remarkably, this system allows catalyst loading as low as 0.01 mol% for β-alkylation of secondary alcohols and 0.005 mol% for the α-alkylation of ketone, delivering access to a wide array of α-alkylated ketones derivatives with yields of ~ 97%. Complex Cat2, in particular, orchestrates one-pot alkylation reactions with a high turnover frequency (TOF) of 5.6  105 h-1 using as low as low catalyst loading of 0.0001 mol%. A comparative study between bimetallic and monometallic complexes reveals that complex Cat2 exhibits better selectivity for the formation of saturated ketones presumably owing to a cooperative effect between the metal centres. The scale-up synthesis highlights the practical applicability of the catalytic approach. To delve into the plausible mechanisms, we conducted initial investigations through meticulously controlled experiments and spectroscopic analysis.