Studies of technetium complexes

The air-stable compounds R[TcNCl4] and R[TcNBr4] (R = [AsPh4]+ or [NBu4sup(n)]+) 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 4dsub(xy) character. The crystal structure of [AsPh4][TcNCl4] has been determined by single-crystal X-ray diffraction methods at 21 deg C. Crystals are tetragonal, space group P4/n. Lattice parameters are reported. 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 Csub(4v) symmetry. Cl-Tc-Cl and N-Tc-Cl bond angles, and Tc-N and Tc-Cl bond distances are given. (U.K.)