Hemilabile Phosphorus Enamine/Imine Ligands And Their Application In Ru-Catalyzed Aqueous Hydration Of Nitriles
AuthorEnow, Raphel Agbor Eyong
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AbstractThe insertion of aromatic nitriles into the C-Li bond of PTA-Li gave a new series of P,N k2-enaminophosphine derivatives (PTA=C(R)NH2) of 1,3,5-triaza-7-phosphaadamantane (PTA), with a characteristic double bond on the PTA cage. Oxidation or sulfuration of the ligands resulted in a mixture of cis-trans products. The cis isomer of oxide converted to the trans, which was isolated. The kinetics and thermodynamic parameters for cis-trans isomerization were obtained. Tungsten tetracarbonyl and ruthenium arene complexes of these new water soluble phosphines were also synthesized. The ligands coordinated in a k2-P,N bidendate fashion to the metal centers to give new iminophosphine complexes. Upon coordination to the metal centers, the ligands were shown to isomerized and tautomerized. All compounds were characterized by NMR (1H, 13C, 31P) and IR spectroscopy, mass spectrometry, and single-crystal X-ray crystallographyThe ruthenium arene complexes were evaluated as potential catalysts for the nitriles hydration in water at 100 °C under air and shown to have good activities as well as a wide range of functional group tolerance. Corresponding in situ catalysts made from RuCl2.3H2O has similar activities as the pre-formed catalysts. Some k2-PN-aminophosphines (PTA-CR2R2NHPh) previous made from our group were used to make another series of ruthenium arene complexes. Turnover numbers as high as 22000 were recorded for nitrile hydration using the k2-PN-aminophosphine ruthenium arene complexes.