Flat and Efficient HCNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction

Abstract

The bidentate HCNN dicarbonyl ruthenium complexes trans,cis-[RuCl2(HCNN)­(CO)2] (1–3) and trans,cis-[RuCl2(ampy)­(CO)2] (1a) were prepared by reaction of [RuCl2(CO)2] n with 1-[6-(4′-methylphenyl)­pyridin-2-yl]­methanamine, benzo­[h]­quinoline (HCNN), and 2-(aminomethyl)­pyridine (ampy) ligands. Alternatively, the derivatives 1–3 were obtained from the reaction of RuCl3 hydrate with HCO2H and HCNN. The pincer CNN cis-[RuCl­(CNN)­(CO)2] (4) was isolated from 1 by reaction with NEt3. The monocarbonyl complexes trans-[RuCl2(HCNN)­(PPh3)­(CO)] (5–7) were synthesized from [RuCl2(dmf)­(PPh3)2(CO)] and HCNN ligands, while the diacetate trans-[Ru­(OAc)2(HCNN)­(PPh3)­(CO)] (8) was obtained from [Ru­(OAc)2(PPh3)2(CO)]. Carbonylation of cis-[RuCl­(CNN)­(PPh3)2] with CO afforded the pincer derivatives [RuCl­(CNN)­(PPh3)­(CO)] (9–11). Treatment of 9 with Na­[BArf]4 and PPh3 gave the cationic complex trans-[Ru­(CNN)­(PPh3)2(CO)]­[BArf 4] (12). The dicarbonyl derivatives 1–4, in the presence of PPh3 or PCy3, and the monocarbonyl complexes 5–12 catalyzed the transfer hydrogenation (TH) of acetophenone (a) in 2-propanol at reflux (S/C = 1000–100000 and TOF up to 100000 h–1). Compounds 1–3, with PCy3, and 6 and 8–10 were proven to catalyze the TH of carbonyl compounds, including α,β-unsaturated aldehydes and bulky ketones (S/C and TOF up to 10000 and 100000 h–1, respectively). The derivatives 1–3 with PCy3 and 5 and 6 catalyzed the hydrogenation (HY) of a (H2, 30 bar) at 70 °C (S/C = 2000–10000). Complex 5 was active in the HY of diaryl ketones and aryl methyl ketones, leading to complete conversion at S/C = 10000.

An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- and Stereoselective Semihydrogenation of Internal and Terminal Alkynes

“…IR spectral analysis of the same solution showed a shift in carbonyl stretching frequencies to 2020 and 2082 cm –1 from the corresponding values 1986 and 2062 cm –1 in 1 (Figure S13). This is consistent with a significant reduction in electron density at the metal center caused by the removal of two iodides and further augmented by two carbonyls.…”

Preparation of monocarbonyl ruthenium complexes bearing bidentate nitrogen and phosphine ligands and their catalytic activity in carbonyl compound reduction

“…Recently, we reported the isolation of [RuH(CO)(dppp)(NN)]Cl from [RuHCl(CO)(PPh3)3] and dppp, 50 a reaction which failed when we used related diphosphines, namely dppb, dppf, limiting the scope of this reaction. 51 In our ongoing interest in the synthesis of carbonyl ruthenium complexes for homogeneous catalysis 52,53 we report herein a general entry for the easy preparation of a series of monocarbonyl ruthenium complexes containing bidentate nitrogen and diphosphine ligands through straightforward syntheses starting from [RuCl2(CO)(dmf)(PPh3)2] and [Ru(OAc)2(CO)(PPh3)2] precursors. The monocarbonyl phosphine ruthenium complexes in the presence of primary amine ligands (i.e.…”

Beyond Metal-Arenes: Monocarbonyl Ruthenium(II) Catalysts for Transfer Hydrogenation Reactions in Cancer Cells

“…Within this framework, we decided to explore a different family of TH organometallic catalysts based on a Ru(II) monocarbonyl scaffold featuring bidentate nitrogen (N^N) and diphosphine (P^P) ligands, of general formula [Ru(OAc)CO(dppb)(N^N)] n (n = +1, 0; dppb = 1,4-bis(diphenylphosphino)butane). Monocarbonyl ruthenium complexes have attracted a great deal of attention in homogeneous catalysis due to their ability to promote several transformations, including in the transfer hydrogenation and hydrogenation of a number of carbonyl compounds [27][28][29][30][31][32] . However, to the best of our knowledge, they have never been tested in TH reactions with the NAD + /NADH couple.…”