Titanium complexes cycloheptatrienyl

The mixed cyclopentadienyl-cycloheptatrienyl ( 5-7 ) titanium complex Cp( -C7H7)Ti has been prepared in 33 -40% yield by the reduction of CpTiCb with isopropylmag-nesium bromide or Mg in the presence of cycloheptatriene. Reduction of Cp TiCb in THF with Mg in the presence of cycloheptatriene gives Cp ( -C7H7)Ti in 68% yield. Titanium 5-7 complexes exhibit sandwich structures see Sandwich Compound) with the five-membered and seven-membered rings nearly parallel to each other. 

The complex shown in Scheme 670 appears to be the first example of an titanium complex. Its reactivity toward cr-donor and 7r-acceptor ligands demostrates that this complex does not behave like a low-valent titanium compound but rather bears a closer resemblance to a Lewis-acidic Ti(iv) complex. Based on theoretical calculations, this behavior can be attributed to a strong and appreciably covalent Ti-cycloheptatrienyl interaction, which leads to highly stabilized frontier orbitals and consequently to a diminishing 7r-electron donor ability.1706... 

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