An Electrochemical Study of Bis(cyclopentadienyl)titanium(IV) Dichloride in the Presence of Magnesium Ions, Amides or Alkynes

Abstract: In tetrahydrofuran, the electrochemical reduction of Cp₂Ti^IVCl₂ (2 mM) generated three titanium(III) complexes which were in equilibrium: [Cp₂TiCl₂]^•−, [Cp₂TiCl]^• and (Cp₂TiCl)₂. Although the anion radical [Cp₂TiCl₂]^•− was the main species produced under these conditions, cyclic voltammetry investigations clearly showed that the proportion of the three electrogenerated Ti^III complexes can be modified as a function of the amounts of chloride ion present in the solution. Accordingly, the presence of Mg²⁺ ions, which led to the consumption of chloride ions through the formation of MgCl₂, favoured the formation of [Cp₂TiCl]^• and, consequently, of the corresponding dimer (Cp₂TiCl)₂. The electrochemical behaviours of Cp₂Ti^IVCl₂ and of the electrogenerated low-valent Ti complexes were also investigated in the presence of amide and alkyne derivatives. Under these conditions, titanium complexes could not only interact with the amide carbonyl group, but also with the alkyne triple bond, provided the latter was not sterically hindered. Interestingly, the carbonyl group and the triple bond had antagonist effects on redox properties of titanium(III) complexes.