CRYSTAL-STRUCTURE OF A BIS(AMIDO)BIS(THIOLATO)OXORHENIUM(V) COMPLEX THAT FORMS A METHANOL-SOLVATED SALT WITH CALCIUM EXTRACTED FROM SILICA-GEL

Complexes of oxorhenium(V) and oxotechnetium(V) with bis(amine)-bis(thiols) have been actively studied in the development of agents for diagnostic imaging (utilizing technetium-99m) or radiotherapy (utilizing rhenium-186 and 188). In the preliminary stages of preparing complexes that might mimic the structure of nonsteroidal estrogens, we prepared complex 2 of the aromatic bis(amine) bis(thiol) chelate 1. The chelate 1 itself was prepared by standard methods (Scheme 1), and the complex 2, isolated after chromatography over silica gel, was obtained as a salt, and was shown by X-ray crystallography, unexpectedly, to have calcium as its counterion. The calcium counterion appears to originate from the chromatographic medium. and in the crystal structure of complex 2, it is solvated by seven molecules of methanol in a novel capped trigonal prism geometry.