Preparation and Properties of Nitridotechnetic(VI) Acid. I. Observation of the E.S.R.-Spectrum of the [TcNF4]- Anion in Hydrofluoric Acid Solution

Abstract

Nitridotechnetic (VI) acid has been prepared by the hydrolysis of Cs2TcNCl5. Dissolution of this compound in concentrated HF gave an e.s.r. spectrum due to [TcNF4: g 1.895, g 1.990, A 0.03765 cm-1, A 0.01795 cm-1, Q 0.00052 cm-1 for Tcvi ; a, 0.0052 cm-l, ay 0.0010 cm-l, az , < 0.0002 cm-1 due to F-. A comparison of the 4dxy MO coefficient, β2, with those for [TcNCI4]- and [TcNBr4]-indicates that the Tc =N bond length is greater in [TcNF4]- than in [TcNCI4]- and [TcNBr4]-.

EPR studies of technetium complexes in frozen solution

“…Correlations between the g-and A-values have been discussed by Raynor etal. [11] and the approximately linear relationship between the g-and A-values and the sum of the ligand spin-orbit coupling constants has been demonstrated by Kirmse et al [22] and Baldas et al [23]. Fig.…”

“…If the acidity of a -0.002 M solution of [TcNC14]-in HC1 is decreased, the spectrum does not change in either intensity or spectral nature until the acidity is reduced below ~3 N. Below this, the spectral intensity and magnetic susceptibility decrease, until below ~0.5 N acid concentration when no EPR is observed [24]. A brown precipitate is formed which can be extracted as the chloride free nitridotechnetic acid, Tc(VI)N(OH)3 [23]. This can be used as the starting material for the formation of complexes in aqueous and non-aqueous solution.…”

EPR Spectroscopy on Technetium Compounds

“…That means that the molecular orbital coefficients ß and ß' and the overlap integrals remain unchanged. Deviations can be observed with ligands which show distinct bonding behaviour like F", NCS" or CN" [10,13,14], Nevertheless, the experimental EPR parameters are a valuable tool to charac- terize instable intermediates in ligand exchange reactions [9][10][11][12][13][14], Direct conclusions on the composition of the equatorial coordination sphere (the ligands in trans-position have been found to have only a very small influence on the EPR parameters [15,16]) can be drawn from resolved superhyperfme interactions due to hgand nuclei. This has been observed for phosphorus (nuclear spin ^'P: / = 1/2) and arsenic (^^As: 1=3/ 2) containing ligands [17][18][19] and Br" / = 3/2) [20], Well-resolved superhyperfme triplets have been obtained in the frozen Solution EPR spectrum of [Tc(NO)Cl3(Me2PhP)2] giving evidence for an equatorial coordination of both phosphine Hgands [21], The spectrum of the corresponding thionitrosyl complex, however, showed only a doublet Splitting of the ^'Tc hyperfme structure lines [17].…”

Technetium Nitrido-Peroxo Complexes: An Unexplored Class of Coordination Compounds

“…A higher yield was achieved following another synthetic route originally proposed by Baldas and coworkers [2]. This procedure first required the in situ generation of nitrido pertechnic acid, [ 99m Tc][Tc(N)(OH) 3 ] n , by aqueous hydrolysis of the nitrido complex [ 99g Tc][Tc(N)Cl 5 ] − [15,16]. The subsequent addition of H 2 O 2 led to the formation of an hypothetical nitrido-peroxo technetic acid, which was further reacted with excess of the appropriate amino acid to yield the final substituted complexes [ 99m Tc][Tc(N)(O 2 ) 2 (L)] − (L = deprotonated Pro, Gly and Ala).…”