Related rhenium(V) catalysts adopt different mechanisms for oxygen atom transfer

✍ Scribed by James H. Espenson

• Book ID: 104010716
• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 594 KB
• Volume: 249
• Category: Article
• ISSN: 0010-8545
• DOI: 10.1016/j.ccr.2004.06.018

✦ Synopsis

The chemical mechanisms for three related rhenium(V) catalysts of oxygen atom transfer reactions are reviewed. Two of the catalysts are compounds with a single rhenium atom, [MeReE(mtp)(PPh3)], where E is either O (1) or S (2) and mtpH 2 is 2-(mercaptomethyl)thiophenol; the third is the di-rhenium compound {MeReO(mtp)} 2 (3). In each of them, the Re atom is square-pyramidal, sitting slightly above the approximate basal plane defined by S, S, C, and P; the oxo or thio group occupies the axial position. They all catalyze oxygen atom transfer from pyridine N-oxides to PAr 3 . The reaction rates are in the orders 3 1 2; even more striking is that the rate laws for the trio of catalysts is distinctly different. This signals the intervention of different chemical steps and intermediates.