Synthesis of cyclopentadienyltricarbonylrhenium(I) carboxylic acid from perrhenate

The cyclopentadienyltricarbonylrhenium(I) carboxylic acid 1, (eta(5)-C5H4COOH)Re(CO)(3), can be quickly prepared from ammonium perrhenate NH4ReO4. The synthetic pathway involves the use of mild conditions to reduce perrhenate to Re-2(CO)(10) followed by a thermal reaction of Re-2(CO)(10) with cyclopentadiene carboxylic acid in mesitylene. The yield from perrhenate is 35%. From pure Re-2(CO)(10), 1 can be obtained with a very good yield of 95%. This new and rapid synthetic pathway may be suitable for the preparation of radiopharmaceuticals. (C) 1999 Elsevier Science S.A. All rights reserved.