20
2 Comprehensive Electrochemistry of Tc …
Table 2.3 Redox potentials
for the
trans–[Tc(or Re)D 2 X 2 ] +/0
couples (Ichimura et al. 1984;
Kirchhoff et al. 1987, 1988)
Solution
Redox couple
E 1/2
versus Ag,AgCl
(3 M KCl)
0.1 M SDS
+ 0.1 M TEAP
in H 2 O
[Tc(dmpe) 2 Cl 2 ] +/0
−0.396
[Re(dmpe) 2 Cl 2 ] +/0
−0.600
[Tc(dmpe) 2 Br 2 ] +/0
−0.300
[Re(dmpe) 2 Br 2 ] +/0
−0.504
[Tc(depe) 2 Cl 2 ] +/0
−0.404
[Re(depe) 2 Cl 2 ] +/0
−0.592
0.5 M TEAP
in DMF
[Tc(diars) 2 Cl 2 ] +/0
−0.061
[Re(diars) 2 Cl 2 ] +/0
−0.319
[Tc(dppe) 2 Cl 2 ] +/0
−0.010
[Re(dppe) 2 Cl 2 ] +/0
−0.205
[Tc(dmpe) 2 Br 2 ] +/0
−0.098
[Re(dmpe) 2 Br 2 ] +/0
−0.297
dmpe: 1,2-bis(dimethylphosphino)ethane
depe: 1,2-bis(diethylphosphino)ethane
diars = 1,2-bis(dimethylarsino)benzene
dppe = 1,2-bis(diphenylphosphino)ethane
Fig. 2.8 Concentration
dependence of the mean
molal ionic activity
coefficients for aqueous
binary solutions of HClO 4 ,
HTcO 4 , and HReO 4 at 25 °C
(Boyd 1978, reprinted with
permission from Boyd
(1978). Copyright 1978
American Chemical Society)
Boyd (1978) determined the activity coefficient, γ ± , of HTcO 4 and HReO 4 acids.
Figure 2.8 shows that the transport properties of the technetium species are almost
the same as for the respective rhenium compounds and this effect is observed for