Trithiacyclononane as a ligand for potential technetium and rhenium radiopharmaceuticals: synthesis of [M(9S3)(SC2H4SC2H4S)][BF4] (M = 99Tc, Re, 188Re) via C-S bond cleavage.
Chemical or electrochemical reduction of the 1,4,7-trithiacyclononane (9S3) complexes [MII(9S3)2][BF4]2 (M = Re (3a) or Tc (3b)) results in instantaneous C-S bond cleavage to yield ethene and the stable MIII thiolate complexes [MIII(9S3)L][BF4] (M = Re (4a) or Tc (4b), L = SCH2CH2SCH2CH2S). Compounds 4 have been characterized by 1H NMR spectroscopy, and the pseudo-octahedral geometry of 4b has been confirmed by X-ray crystallography. Upon electrochemical reduction 4a loses ethene, while 4b can be reversibly reduced to [TcII(9S3)L], which is then further reduced to Tc(I) with loss of ethene. Successive ethene loss is observed in the mass spectra of compounds 3 and 4. The radiosynthesis of 4a with 188Re can be comfortably completed within 10 min starting with 188ReO4- from a 188W/188Re generator, with a radiochemical yield in excess of 90%, and thus represents a practical approach to the preparation of stable 188Re (and 99mTc) thioether complex derivatives/conjugates for clinical use. Crystal data: 4b, C10H20S6Tc, orthorhombic Pbca, a = 12.233(2) A, b = 14.341(2) A, c = 20.726(3) A, Z = 8.
Mullen
G E
GE
School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NR, U.K.
Blower
P J
PJ
Price
D J
DJ
Powell
A K
AK
Howard
M J
MJ
Went
M J
MJ
D000473:Alkanes / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D018360:Crystallography, X-Ray; D008024:Ligands; D015394:Molecular Structure; D019275:Radiopharmaceuticals / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry*; D013057:Spectrum Analysis; D013455:Sulfur / Q000737:chemistry; D013457:Sulfur Compounds / Q000737:chemistry*; D017556:Technetium Compounds / Q000737:chemistry*
D000473:Alkanes; D008024:Ligands; D019275:Radiopharmaceuticals; D013457:Sulfur Compounds; D017556:Technetium Compounds; C421311:trithiacyclononane; D013455:Sulfur; D012211:Rhenium; D002244:Carbon