PROTECTING GROUPS IN THE PREPARATION OF THIOLATE COMPLEXES OF TECHNETIUM

The nitrogen-sulfur ligand H2PIC(Acm) (N-(2-((2-(((acetylamino)methyl)thio)acetyl)amino)ethyl)-2-pyridinecarboxamide) reacted with (Bu4N)[TcOCl4] in methanolic solution, yielding the neutral complex [TcO(PIC)] (oxo[N-(2-((2-mercaptoacetyI)amino)ethyl)-2-pyridinecarboxamido]technetium(V)) as a red crystalline solid. The thiol-protected derivatives H2PIC(Bzm) (Bzm = (benzoylamino)methyl) and H2PIC(Bzl) (Bzl = benzyl) similarly gave [TcO(PIC)] in near-quantitative yield. In contrast, reaction of the unprotected, free-thiol form of the ligand, H3PIC, with (Bu4N)[TcOCl4] in methanol gave a highly colored mixture of reduced technetium species and only traces of the neutral product. The ligand H2PYR(Bzm) also reacted with (Bu4N)[TcOCl4] in methanol, giving a red neutral complex [TcO(PYR)]. The X-ray structure of [TcO(PIC)] was determined. Crystal data for [TcO(PIC)]: [C10H10N3O3STc], tetragonal, MW = 349.27, a = 8.010 (0) Å, c = 36.845 (0) Å, space group = P432,2, Z = 8, R = 0.037, Rw = 0.041. © 1990, American Chemical Society. All rights reserved.