| Abstract
| - The formally Ti(I)/Ti(II) mixed-valence toluene complex {2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}Ti(μ,η6-C7H8)Ti[{2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}][K(DME)2]·toluene (1) with an inverse sandwich-type structure has been obtained from the reduction of {2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}TiCl with potassium in toluene.
- The formally Ti(I)/Ti(II) mixed-valence toluene complex {2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}Ti (μ,η6-C7H8)Ti[{2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}][K(DME)2]·toluene (1) with an inverse sandwich type ofstructure has been obtained from the reduction of {2,5-[(C4H3N)CPh2]2[C4H2N(Me)]}TiCl with potassiumin toluene. The bridging molecule of toluene in the paramagnetic 1 shows a visible distortion due to asubstantial amount of metal-to-ring back-bonding. Complex 1 was always the only detectable product,even in cases when lower than stoichiometric amounts of reductant were employed. DFT calculationshave been carried out to elucidate the electronic structure of the mixed-valence 1 in order to clarify thereason for its apparent thermodynamic stability. The most energetically favorable model comprises twodivalent Ti centers connected to an organic radical anion. The olefin adducts {2,5-[(C4H3N)CPh2]2[C4H2N]}Ti(η2-trans-PhHCCHPh)[K(DME)] (2) and {2,5-[(C4H3N)CPh2]2[C4H2N (Me)]}Ti(η2-trans-PhHCCHPh) (3) were obtained from identical reactions carried out in the presence of trans-stilbene.Complexes 2 and 3 may be regarded as the result of the oxidative addition of a transient divalent speciesto the trans-stilbene molecule. In the case of 2 however, the reaction is accompanied by the cleavage ofthe C−N bond of the π-bound alkylated pyrrole ring.
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