Probing the effect of heterocycle-bonding in PNX-type ruthenium pre-catalysts for reactions involving H₂

Abstract

A series of ruthenium(ii) complexes with three novel PNX-type pincer ligands is reported, in which X denotes a heterocyclic donor group (PNX = Ph2PCH2CH2N(H)CH2-X, X = 2-pyridyl, 2-furanyl, 2-thiophenyl or 2-pyrrolyl). The reaction of [(Ph3P)3RuCl2] with one equivalent of ligand leads to the trans-dichloro complexes [(PNX)RuCl2(PPh3)] (1-4) for all ligands, whereas the complexation of [(Ph3P)3Ru(H)(Cl)(CO)] results in different types of complexes. The variation of the heterocyclic donor group is in line with different binding properties and a labilization of this group. Investigations on the catalytic activity of different types of ruthenium(ii) complexes in hydrogenation and dehydrogenation reactions reveal that more labile bound heterocycle donors result in a decrease of catalytic productivity and activity.

Dehydrogenative Coupling of Ethanol and Ester Hydrogenation Catalyzed by Pincer-Type YNP Complexes

“…Xu and Langer recently tested our RuCl 2 (PPh 3 )-[PiNHCH 2 CH 2 PPh 2 ] ( 13) catalyst and the related complexes 14−16 of Chart 2 in the acceptorless dehydrogenative coupling of benzyl alcohol. 10 Their experiments gave 1210 (13), 52 (14), 140 (15), and 20 turnovers ( 16) to benzyl benzoate. This and other observations of Xu and Langer suggested, in the words of the authors, that "with the weakening ruthenium−heteroatom bond the catalytic activity of these ruthenium pre-catalysts in the acceptorless dehydrogenation of primary alcohols as well as the hydrogenation of ketones is diminished".…”

“…Xu and Langer recently tested our RuCl 2 (PPh 3 )­[PiNHCH 2 CH 2 PPh 2 ] ( 13 ) catalyst and the related complexes 14 – 16 of Chart in the acceptorless dehydrogenative coupling of benzyl alcohol . Their experiments gave 1210 ( 13 ), 52 ( 14 ), 140 ( 15 ), and 20 turnovers ( 16 ) to benzyl benzoate.…”

A One-Step Preparation of Tetradentate Ligands with Nitrogen and Phosphorus Donors by Reductive Amination and Representative Iron Complexes

“…By 31 P NMR (Figure S2), we observed only ∼2% diphenylphosphine, superior to commercial samples. Compound 1 is an important ligand in hydrogenation catalysis. ,,− …”

Ball mill and microwave assisted synthetic routes to Fluoxetine

“…Data in agreement with the literature. (Xu et al 2015). Aminoketone hydrochloride 3a (107 mg, 0.5 mmol) and NaBH4 (25 mg, 0.65 mmol) were added into a 25 mL stainless steel grinding jar with a 25 mm Ø stainless steel ball.…”