Header menu link for other important links
X
Bifunctional water activation for catalytic hydration of organonitriles
P. Daw, , S.M.W. Rahaman, S. Dinda, J.K. Bera
Published in
2012
Volume: 31
   
Issue: 9
Pages: 3790 - 3797
Abstract
Treatment of [Rh(COD)(μ-Cl)] 2 with excess tBuOK and subsequent addition of 2 equiv of PIN•HBr in THF afforded [Rh(COD)(κC 2-PIN)Br] (1) (PIN = 1-isopropyl-3-(5,7-dimethyl-1, 8-naphthyrid-2-yl)imidazol-2-ylidene, COD = 1,5-cyclooctadiene). The X-ray structure of 1 confirms ligand coordination to "Rh(COD)Br" through the carbene carbon featuring an unbound naphthyridine. Compound 1 is shown to be an excellent catalyst for the hydration of a wide variety of organonitriles at ambient temperature, providing the corresponding organoamides. In general, smaller substrates gave higher yields compared with sterically bulky nitriles. A turnover frequency of 20 000 h -1 was achieved for the acrylonitrile. A similar Rh(I) catalyst without the naphthyridine appendage turned out to be inactive. DFT studies are undertaken to gain insight on the hydration mechanism. A 1:1 catalyst-water adduct was identified, which indicates that the naphthyridine group steers the catalytically relevant water molecule to the active metal site via double hydrogen-bonding interactions, providing significant entropic advantage to the hydration process. The calculated transition state (TS) reveals multicomponent cooperativity involving proton movement from the water to the naphthyridine nitrogen and a complementary interaction between the hydroxide and the nitrile carbon. Bifunctional water activation and cooperative proton migration are recognized as the key steps in the catalytic cycle. © 2012 American Chemical Society.
About the journal
JournalOrganometallics
ISSN02767333