Synthesis and characterization of a technetium nitrido dimer

In 1993, Baldas et al. [1] reported the synthesis of the technetium(VI) nitridodi (μ-oxo) dimer (AsPh4)2[{TcNCl2}2(μ-O)2], which was synthesized from methanesulfonic acid and Cs2[TcNCl5] in water with heating. We report here, the facile synthesis and characterization of the tetrabutylammonium analog, (Bu4N)2[{TcNCl2}2(μ-O)2] (1), which is synthesized from (Bu4N)[TcNCl4] and water in acetone at room temperature. This may have important ramifications for technetium based radiopharmaceutical development, since [99mTcNCl4]− is frequently employed at the tracer level as a technetium nitrido synthon, and technetium nitrido chemistry continues to be a rapidly developing area in radiopharmaceutical research [1]. The infrared spectrum of 1 displays a pronounced absorption at 1062 cm−1, attributed to the TcN bond. The FAB(−) mass spectrum displays the parent ion of 642 m/z which corresponds to {(Bu4N)[{TcNCl2}2(μ-O)2]}−. The X-ray crystal structure of 1 is similar to the previously reported tetraphenylarsonium analog [2]. The technetium nitrogen triple bond lengths are 1.601(7) and 1.597(7) Å. The X-ray structure solution for C32H72Cl4N2O4Tc of molecular weight 886.72 g mol−1: Monoclinic space group P21/n, a=15.2894(12), b=16.4321(12), c=17.9311(14) Å, β=105.5100(10)°, volume=4340.9(6) Å3. Solution based on 6212 independent reflections to give a final R value of 0.0701 and GOF=1.124.