Hydrogenation of imines catalyzed by ruthenium(II) complexes containing phosphorus-nitrogen ligands via hydrogen transfer reaction

Aranda, Braulio; Valdebenito, Gonzalo; Parra-Melipán, Sebastián; López, Vicente Fidel; Moya, Sergio A.; Vega, Andrés; Aguirre, Pedro

doi:10.1016/j.mcat.2022.112374

Cited by 3 publications

(1 citation statement)

References 31 publications

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“…Complexes 1 – 4 showed no observable activity. Further catalytic investigations were carried out using complexes 1 – 4 (1 mol %) in the asymmetric transfer hydrogenation of diphenylphosphinoyl imines to their respective amines analogues using KO t Bu (8 mol %) as a base and 2-PrOH as a solvent and as a reducing agent at 30 °C. ,, After 24 h, no conversion was noted using 31 P NMR spectroscopy to monitor the reaction. We envisaged the possible activation of the complexes by the generation of their corresponding hydrides using LiHBEt 3 in THF at −30 to 28 °C to induce their catalytic activity in transfer hydrogenation. , The formation of hydrides was not successful.…”

Section: Resultsmentioning

confidence: 99%

Mechanochemical Synthesis of Chromium(III) Complexes Containing Bidentate PN and Tridentate P-NH-P and P-NH-P′ Ligands

Ajayi,

Lough,

Morris

2024

ACS Omega

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Chromium(III) complexes bearing bidentate {NH2(CH2)2PPh2: PN, (S,S)-[NH2(CHPh)2PPh2]: P’N} and tridentate [Ph2P(CH2)2N(H)(CH2)2PPh2: P-NH-P, (S,S)-(iPr)2PCH2CH2N(H)CH(Ph)CH(Ph)PPh2: P-NH-P′] ligands have been synthesized using a mechanochemical approach. The complexes {cis-[Cr(PN)Cl2]Cl (1), cis-[Cr(P’N)Cl2]Cl (2), mer-Cr(P-NH-P)Cl3 (3), and mer-Cr(P-NH-P′)Cl3 (4)} were obtained in high yield (95–97%) via the grinding of the respective ligands andthe solid Cr(III) ion precursor [CrCl3(THF)3] with the aid of a pestle and mortar, followed by recrystallization in acetonitrile. The isolated complexes are high spin. A single-crystal X-ray diffraction study of 2 revealed a cationic chromium complex with two P’N ligands in a cis configuration with P′ trans to P′ with chloride as the counteranion. The X-ray study of 4 shows a neutral Cr(III) complex with the P-NH-P′ ligand in a mer configuration. The difference in molecular structures and bulkiness of the ligands influence the electronic, magnetic, and electrochemical properties of the complexes as exhibited by the bathochromic shifts in the electronic absorption peaks of the complexes and the relative increase in the magnetic moment of 3 (4.19 μβ) and 4 (4.15 μβ) above the spin only value (3.88 μβ) for a d3 electronic configuration. Complexes 1–4 were found to be inactive in the hydrogenation of an aldimine [(E)-1-(4-fluorophenyl)-N-phenylmethanimine] under a variety of activating conditions. The addition of magnesium and trimethylsilyl chloride in THF did cause hydrogenation at room temperature, but this occurred even in the absence of the chromium complex. The hydrogen in the amine product came from the THF solvent in this novel reaction, as determined by deuterium incorporation into the product when deuterated THF was used.

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