C–H Activation at a Ruthenium(II) Complex – The Key Step for a Base‐Free Catalytic Transfer Hydrogenation?1. Issue 24 (1st July 2013)

• Record Type: Journal Article
• Authors: Taghizadeh Ghoochany, Leila; Kerner, Christian; Farsadpour, Saeid; Menges, Fabian; Sun, Yu; Niedner‐Schatteburg, Gereon; Thiel, Werner R.
• Is Part Of: European journal of inorganic chemistry. Issue 24(2013)
• Page Start: 4305
• Page End: 4317
• Publication Date: 2013-07-01
• Subjects: Transfer hydrogenation -- Ruth­enium -- C–H activation -- Mass spectrometry -- Density functional calculations; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201300480
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: Ruthenium(II) complexes [(η 6 ‐cymene)RuCl(apypm)]BPh4 with bidentate 2‐amino‐4‐(2‐pyridinyl)pyrimidine (apypm) ligands catalyze the transfer hydrogenation of acetophenone. Their activities are strongly dependent on the substituent pattern of the pyrimidine ring. Complexes bearing a primary amino group in the 2‐position of the pyrimidine ring do not perform the catalysis in terms of a "bifunctional mechanism", although they possess protic hydrogen atoms at the amino moiety in close proximity to the metal site. Systems containing tertiary dialkylated amino substituents at the apypm ligand are the first examples of air‐stable and phosphane‐free transfer‐hydrogenation catalysts that show high activities even in the absence of a base. A new mechanism for the catalyst activation in the absence of an external base is proposed on the basis of ESI‐MS investigations and ab initio calculations combined with isotope labelling: C–H bond cleavage at the pyrimidine ring is the crucial step for the generation of the catalytically active species. Abstract : Phosphane‐free air‐stable ruthenium complexes catalyze the transfer hydrogenation of acetophenone in the absence of a base. Intramolecular C–H bond cleavage gives rise to a new catalyst activation mechanism, which was investigated through isotopic labelling, mass spectrometry and quantum chemical calculations.