Studies of technetium complexes. Part 6. The preparation, characterisation, and electron spin resonance spectra of salts of tetrachloro- and tetrabromo-nitridotechnetate(VI): crystal structure of tetraphenylarsonium tetrachloronitridotechnetate(VI)

Abstract

The e.s.r. spectra of [TcNCI,] -and [TcNBr,] -are typical of ions with a 4d1 electronic configuration and the unpaired electron in an orbital with substantial 4dx, character. The crystal structure of [AsPh,] [TcNCI,] has been determined by single-crystal X-ray diffraction methods at 21 "C. Crystals are tetragonal, space group P4/n, with a = 12.707(2), c = 7.793(1) A, and 2 = 2. Full-matrix least-squares refinement gave a final R value of 0.031 for 1 079 independent reflections. The compound is isostructural with the series [AsPh,][MNCI,] * Supplementary data available (No. SUP 56030, 4 pp.

The Synthesis of TcNCI3; New Approaches to TcNCl4 -

“…The crystalline, red technetium tetrachloride TcCU reacts with iodine azide in CCU to yield a very moisture sensitive, black brown powder which is nearly insoluble in all common solvents. The same product can be obtained by treating (Bu4N) (3) of the tetrachlorogallat anion which remains in Solution. The insoluble technetium nitride chloride has a Polymerie structure, most probably connected by chloro and nitrido bridges.…”

“…From the orange-red Solution (Ph4As)[TcNCU] could be isolated and characterized by its melting point, infrared spectrum and EPR spectrum [3],…”

“…After 1 h the cooling was removed and the mixture was stirred for 5 days at room temperature. The reaction was completed by refluxing which has been described earlier by several authors [12], The products were characterized by elemental analysis, their melting points (180 °C) [3]), the infrared spectra (Tc = N 1080 cm" ^ [3]) and ESR-spectra (go = 2.005, = 187 10-'^cm-^ = 2.008; Af = 293.0 • lO-'^ cm-'; g, = 2.000, A^' = 136 • lO-'^cm"' [12]). …”

Final Report, Research Program to Investigate the Fundamental Chemistry of Technetium

“…In order to pursue these investigations, however, it was first necessary to devise improved methods for preparation of common starting materials. A number of technetium and rhenium complexes possessing terminal oxo or nitrido groups and halide ligands have been reported in the literature, but their widespread use has been hindered by difficult and low-yield syntheses (Cotton 1979, Davison 1982, Nelson 1954, Rulfs 1955, Liese 1981, Baldas 1991, Cotton 1966, Rose 1996, Baldas 1984 -, and MOX 3 (L) 2 (M = Tc, Re; X = Cl, Br, I; L = THF, MeCN) were devised. Vibrational and electronic spectroscopies proved best suited to characterize the metal oxohalide complexes; EPR spectroscopy was also utilized to examine the paramagnetic species in the series.…”

“…This observation is significant in light of the fact that nitrogen-based reductants such as hydrazine and hydroxylamine are commonly used to generate Tc(IV) in situ for environmental speciation and stability studies (Pikaev 1996). The technetium nitride moiety is quite robust under a range of conditions, and its behavior is very different from that of Tc(IV) (Baldas 1991, Baldas 1986, Baldas 1984. Reduction of pertechnetate with hydroxylamine in the presence of complexants appears to be significantly slower than reductions using hydrazine under comparable conditions.…”