KINETIC AND EQUILIBRIUM STUDY OF SUBSTITUTION-REACTIONS OF TRANS-TETRACYANODIOXORHENATE(V) IONS WITH MONODENTATE NUCLEOPHILES

The kinetics of the substitution reactions of the protonated forms of trans-tetracyanodioxorthenate(V) with thiourea (TU), N-methylthiourea (NMTU), N,N'-dimethylthiourea (NNDMTU) and hydrazoic acid (HN3) were studied. The results were compared with those obtained for similar reactions of [WO2(CN)4]4-. This study showed that the diprotonated form [ReO(H2O)(CN)4]- is the only species reactive towards substitution reactions (and not the [ReO(OH)(CN)4]2- ion) and that only the aqua ligand in [ReO(H2O)(CN)4]- is substituted by the incoming group. A dissociative mechanism is proposed for the substitution reactions between [ReO(H2O)(CN)4]- and the monodentate nucleophiles. The i.r. data for these Re(V) complexes are reported and discussed in terms of the relative trans influence of the various monodentate ligands.