Mixed rhenium(I) tricarbonyl complexes for the development of radiopharmaceuticals for CNS-receptor imaging

The agostic B-H...Re bond in complex [Re{kappa³-H(µ-H)B(tim^Me)₂}(CO)₃] (1) (tim^Me=2-mercapto-1-methylimidazolyl) is easily cleaved by functionalized isonitriles, bearing a (2-methoxyphenyl)piperazine moiety (part of WAY 100635), leading to the novel complexes [Re{kappa³-H(µ-H)B(tim^Me)₂}(C=NR-WAY)(CO)₃] (R= butylene (4), pentylene (5) or hexylene (6)). These mixed Re(I) tricarbonyl complexes (4-6) have been fully characterized by the usual analytical techniques, which included X-ray diffraction analysis in case of 4. Complexes 4-6 can be seen as suitable surrogate molecules of potential ^99mTc-radiopharmaceuticals for imaging of 5-HT_1A subtype of serotonin receptors.