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

Theoretically, several complexes can be formed during the reaction between the tridentate aminedithiol ligand EtN(CH2CH2SH)(2), L1H(2), the monodentat e thiol p-ClC6H4SH, L2H, and the (ReOCl3)-O-V(PPh3)(2). Three main possibil ities are: (i) neutral mixed ligand complexes ReOL1L2, the syn isomer, comp lex 1 and the anti isomer, complex 2; (ii) binuclear complex of the trident ate ligand, (ReO)(2)(L1)(3), complex 3 and (iii) anionic complex of the mon othiol [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 th e complexes 3 and 4 are formed under the above reaction conditions. The oxo rhenium complexes 3 and 4 have been synthesized by the reaction of L1H(2) o r L2H respectively with the precursor ReOCl3(PPh3)(2). The crystal structur es of 1, 3, and 4 are determined by X-ray crystallography. The correspondin g Tc-99m complexes have been prepared by exchange reaction using Tc-99m-glu coheptonate as precursor. Similarly the major reaction product is the syn i somer, complex 1', while none of the other complexes are formed during the reaction at tracer level. The above studies demonstrate that simultaneous a ction of a tridentate SNS ligand and a monodentate thiol in equimolar quant ities on (ReOCl3)-O-V(PPh3)(2) or Tc-99m-glucoheptonate leads to a single r henium or technetium-99m species, the syn MOL1L2. (C) 1999 Elsevier Science S.A. All rights reserved.