Keywords: Transfer hydrogenation / Ruthenium / C-H activation / Mass spectrometry / Density functional calculationsRuthenium(II) complexes [(η 6 -cymene)RuCl(apypm)]BPh 4 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 contain-
A series of ruthenium complexes of the general formula [RuCl2(L)(NNN)] were synthesized starting from tridentate N,N,N‐ligands containing pyridine and allylated pyrazole donor groups and [RuCl2(PPh3)3]. The N,N,N‐donors introduced herein are accessible in a few steps from versatile precursors. The primary products, [RuCl2(NNN)(PPh3)], can be converted into the corresponding carbonyl complexes, [RuCl2(CO)(NNN)], by bubbling CO into a solution in toluene at elevated temperatures. All ruthenium complexes were investigated as catalysts for the transfer hydrogenation of aryl ketones. The phosphane complexes show high activities with turnover frequency values of up to 1200 h–1 in the presence of just one equivalent of KOH, whereas the carbonyl complexes are only poorly active.
Palladium complexes synthesised from (C 6 H 5 CN) 2 PdCl 2 and (2-aminopyrimidinyl)phosphanes show different coordination modes depending on the nature of the amino substituent attached to the pyrimidine ring. Whereas P,N-coordination is observed for primary and secondary amino groups, tertiary amino groups lead to C-H activation at the pyrimidine ring.
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