Exceptionally Active Assembled Dinuclear Ruthenium(II)-NNN Complex Catalysts for Transfer Hydrogenation of Ketones

Abstract

Dinuclear ruthenium(II)-NNN complexes were efficiently assembled by means of coordinatively unsaturated 16-electron mononuclear ruthenium(II)-pyrazolyl-imidazolyl-pyridine complex and 4,4′-linked bipyridine ligands. The diruthenium(II)-NNN complex assembled through 4,4′-(CH 2 ) 3bipyridine exhibited exceptionally high catalytic activity for the transfer hydrogenation (TH) of ketones in refluxing 2-propanol and reached TOF values up to 1.4 × 10 7 h −1 , demonstrating a remarkable cooperative effect from the ruthenium(II)-NNN functionalities.

Ruthenium(II) Complexes of 4′‐(Aryl)‐2,2′:6′,2′′‐terpyridyl Ligands as Simple Catalysts for the Transfer Hydrogenation of Ketones

“…An extensive exploration of ruthenium catalysts with NNN tridentate pincer ligands for the TH of ketones has occurred over the past few years (Scheme ). [1c], Yu et al synthesized several NNN pincer‐type ligands and their corresponding ruthenium(II) complexes for the TH of ketones with or without acceleration functionality . For example, the air‐ and moisture‐stable ruthenium(II) complex A exhibited excellent TH activity for ketones in 2‐propanol under reflux owing to the hemilabile unsymmetrical coordination environment and the NH functionality.…”

“…For example, the air‐ and moisture‐stable ruthenium(II) complex A exhibited excellent TH activity for ketones in 2‐propanol under reflux owing to the hemilabile unsymmetrical coordination environment and the NH functionality. [14f] Complex B , bearing a (trifluoromethyl)pyrazolyl functionality, converted ketones to their corresponding alcohols in maximum yields of 99 %. [14d] The room‐temperature transfer hydrogenation of ketones and aldehydes was achieved in 2‐propanol with the ruthenium(II) complex C as the catalyst under aerobic conditions.…”

“…[14f] Complex B , bearing a (trifluoromethyl)pyrazolyl functionality, converted ketones to their corresponding alcohols in maximum yields of 99 %. [14d] The room‐temperature transfer hydrogenation of ketones and aldehydes was achieved in 2‐propanol with the ruthenium(II) complex C as the catalyst under aerobic conditions. [14k] Li and co‐workers developed a ruthenium(II) complex ( D ) with a symmetrical pyridyl‐2,6‐pyrazolyl ligand, which showed good‐to‐excellent catalytic activity in transfer hydrogenation with a wide range of ketone substrates.…”

“…[14d] The room‐temperature transfer hydrogenation of ketones and aldehydes was achieved in 2‐propanol with the ruthenium(II) complex C as the catalyst under aerobic conditions. [14k] Li and co‐workers developed a ruthenium(II) complex ( D ) with a symmetrical pyridyl‐2,6‐pyrazolyl ligand, which showed good‐to‐excellent catalytic activity in transfer hydrogenation with a wide range of ketone substrates. [13e] Song and co‐workers also reported a symmetrical Ru II complex ( E ) and observed almost quantitative transfer hydrogenation of ketones with wide substrate scope.…”

Ru(II)‐PBTNNXN complex bearing functional 2‐(pyridin‐2‐yl)benzo[d]thiazole ligand catalyzed α‐alkylation of nitriles with alcohols

“…It can dramatically promote the catalytic activity applied in borrowing hydrogen catalysis using ligands containing functional groups such as NH [33][34][35][36][37] and OH [38][39][40] . Among them, NNN ligands [41][42][43] bearing NH [44,45] coordinated with Ru metal could be potential chelating ligands due to their synthetic accessibility and excellent air-and moisture-stability compared to phosphine ligands.…”