Study on the formation of mixed ligand oxorhenium and oxotechnetium complexes (SNS/S combination)

摘要

Theoretically, several complexes can be formed during the reaction between the tridentate aminedithiol ligand EtN(CH_2CH_2SH)_2, L1H_2, the monodentate thiol p-ClC_6H_4SH, L2H, and the rE~vOCl_3(PPh_3)_2. Three main possibilities are: (i) neutral mixed ligand complexes ReOL1L2, the syn isomer, complex 1 and the anti isomer, complex 2; (ii) binuclear complex of the tridentate ligand, (ReO)_2(L1)_3, complex 3 and (iii) anionic complex of the monothiol [ReO(L2)_4]~-, complex 4. When a mixture of L1H_2/L2H, 1/1 ratio, is applied, the major product of the reaction is the syn isomer 1. A small amount of the anti isomer 2 is also isolated (yield <2%) while none of the complexes 3 and 4 are formed under the above reaction conditions. The oxorhenium complexes 3 and 4 have been synthesized by the reaction of L1H_2 or L2H respectively with the precursor ReOCl_3(PPh_3)_2. The crystal structures of 1, 3 and 4 are determined by X-ray crystallography. The corresponding ~(99m)Tc complexes have been prepared by exchange reaction using ~(99m)-Tc-glucoheptonate as precursor. Similarly the major reaction product is the syn isomer, complex 1', while none of the other complexes are formed during the reaction at tracer level. The above studies demonstrate that simultaneous action of a tridentate SNS ligand and a monodentate thiol in equimolar quantities on Re~vOCl_3(PPh_3)_2 or ~(99m)Tc-glucoheptonate leads to a single rhenium or technetium-99m species, the syn MOL1L2.