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 air-stable compounds R[TcNCl4] and R[TcNBr4](R =[AsPh4]+ or [NBun4]+) have been prepared by the reaction of [NH4][TcO4] with NaN3 in the presence of concentrated HCl or of HBr. The e.s.r. spectra of [TcNCl4]– and [TcNBr4]– are typical of ions with a 4d1 electronic configuration and the unpaired electron in an orbital with substantial 4dxy character. The crystal structure of [AsPh4][TcNCl4] 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 Z= 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 [AsPh4][MNCl4](M = Mo, W, Re, Ru, or Os) and with [AsPh4][MOCl4](M = Mo or Re). The [TcNCl4]– anion in [AsPh4][TcNCl4] possesses C4v symmetry with Cl–Tc–Cl bond angles of 86.95(1) and 153.33(6)° and NTc–Cl bond angles of 103.34(3)°. The TcN bond distance is 1.581 (5)A and the Tc–Cl distances are 2.3220(9)A.