Redox potentials and reduction experiments

The stability of oxidation states of the heaviest elements, and the influence of relativistic effects, can be investigated by reduction experiments. For that purpose, knowledge of relative stabilities of oxidation states, redox potentials E°, is of crucial importance E° is needed to decide which reducing or oxidizing agent should be chosen to reach the desired state. 

One of the first ideas to study unusual oxidation states caused by relativistic effects was an attempt to reduce Lr The relativistic stabilization of the 7pi/2 electron in the ground state of Lr (7s 7pi/2) was the reason to expect an enhanced stability of the 1+ oxidation state in contrast to the stable 3+ state of the lanthanides. Attempts to reduce Lr with and Cr in dilute HCl were, however, unsuccessful and a limit on the reduction potentials of the Lr /Lr couple was estimated as -0.44 V [204]. Later attempts to reduce Lr with Sm and coprecipitate Lr with Rb by using sodium tetraphenylborate or chloroplatinic acid were also unsuccessful, and the upper limit for the Lr /Lr couple of -1.56 V was estimated making it unlikely that Lr can exist in aqueous solutions [205]. There were similar ideas to reduce Db to Db and Sg to to check the stability of the lower oxidation states caused, as was 

A way to obtain the redox potential is to calculate the fi ee energy change AG° of an oxidation-reduction reaction 

The redox potential E° is then defined by the well-known equation 

Results of those investigations have, indeed, shown that the stability of the maximum oxidation state increases in group 4 through 6, while that of lower oxidation states decreases. Along the 6d series, the stability of the maximum oxidation state decreases = -2.6 V, (Rf /Rf ) = -1.5 V, 

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