Synthesis of hydroxyl silylated rhenium and (^99mTc)technetium "3+1" oxo-complexes with the H₂PNS tridentate ligand

Oxo-complexes of general formula [^99mTc(O)(PNS)(S(CH₂)_nOSiR₃)] (3a-c) were synthesized by direct reduction of [^99mTcO₄]^- with stannous chloride in the presence of the tridentate H₂PNS and of the monodentate [HS(CH₂)_nOSiR₃] ligands (n=2, R=Ph; (1a); n=3, R=Ph, (1b); n=3, R=Et, (1c)). The ^99mTc complexes were characterized by comparison of their HPLC profiles with the analogous rhenium complexes (2a-c). Complexes 3a-c were obtained with high radiochemical purity (>95%) and their stability was investigated in PBS pH 7.4, rat plasma and against glutathione, at 37°C. The pH influence on the cleavage of the O-Si bond was also investigated.