Ruthenium NNN complexes with a 2‐hydroxypyridylmethylene fragment for transfer hydrogenation of ketones

E-ISSN： 1099-0739|32|2|aoc.4100-aoc.4100

ISSN： 0268-2605

Source： APPLIED ORGANOMETALLIC CHEMISTRY (ELECTRONIC), Vol.32, Iss.2, 2018-02, pp. : n/a-n/a

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Abstract

Four NNN tridentate ligands L₁–L₄ containing 2‐methoxypyridylmethene or 2‐hydroxypyridylmethene fragment were synthesized and introduced to ruthenium centers. When (HOC₅H₃NCH₂C₅H₃NC₅H₇N₂) (L₂) and (HOC₅H₃NCH₂C₅H₃NC₆H₆N₃) (L₄) reacted with RuCl₂(PPh₃)₃, two ruthenium chloride products Ru(L₂)(PPh₃)Cl₂ (1) and Ru(L₄)(PPh₃)Cl₂ (2) were isolated, respectively. Reactions of (MeOC₅H₃NCH₂C₅H₃NC₅H₇N₂) (L₁) and (MeOC₅H₃NCH₂C₅H₃NC₆H₆N₃) (L₃) with RuCl₂(PPh₃)₃ in the presence of NH₄PF₆ generated two dicationic complexes [Ru(L₁)₂][PF₆]₂ (3) and [Ru(L₃)₂][PF₆]₂ (4), respectively. Complex 1 reacted with CO to afford product [Ru(L₂)(PPh₃)(CO)Cl][Cl]. The catalytic activity for transfer hydrogenation of ketones was investigated. Complex 1 showed the highest activity, with a turnover frequency value of 1.44 × 10³ h⁻¹ for acetophenone, while complexes 3 and 4 were not active.