NEUTRAL, 7-COORDINATE DIOXIME COMPLEXES OF TECHNETIUM(III) - SYNTHESIS AND CHARACTERIZATION

The tin-capped complexes 99Tc(oxime)3(μ-OH)SnCl3 [oxime = dimethylglyoxime (DMG) or cyclohexanedione dioxime (CDO)] can be prepared by the reduction of NH4TcO4 with 2 equiv of SnCl2 in the presence of dioxime and HCl. These tin-capped complexes can be readily converted into a new class of uncapped Tc–dioxime compounds, TcCl(oxime)3, by treatment with HCl. This reaction is reversible. Both the tin-capped and uncapped tris(dioxime) complexes can be converted to the previously reported boron-capped Tc–dioxime complexes TcCl(oxime)3BR (R = alkyl, OH) by reaction with boronic acids or with boric acid at low pH. All of these complexes [Tc(oxime)3(μ-OH)SnCl3, TcCl(oxime)3, and TcCl(oxime)3BR] appear to be neutral, seven-coordinate compounds of technetium(III). They have been characterized by elemental analysis, 1H NMR and UV/visible spectroscopy, conductivity, and fast atom bombardment mass spectrometry. The synthesis, characterization, and reactivity of these compounds is discussed. The X-ray crystal structure analysis of TcCl(DMG)3 and an abbreviated structure report on TcCI(DMG)3MeB are described. Crystal data for TcCl(DMG)3: a = 9.617 (1) Å, b = 12.135 (3) Å, c = 9.244 (2) Å, a = 110.24 (2)°, β = 92.36 (2)°, γ = 88.92 (2)°, space group = Pl,Z = 2. Final R = 0.041; Rw = 0.047. Data for TcCl(DMG)3MeB: a = 20.290 (3) Å, b = 14.468 (2) Å, c = 16.404 (3) Å, β = 124.65 (1)°, space group = C2/c, Z = 8. Final R = 0.039; Rw = 0.044. © 1990, American Chemical Society. All rights reserved.