Biscyclopentadienyltitanium(III) chloride dimer

Alkyne [2 + 2 + 2] Cyclotrimerization Catalyzed by a Low-Valent Titanium Reagent Derived from CpTiX3 (X = Cl, O-i-Pr), Me3SiCl, and Mg or Zn

“…Low-valent titanium (LVT) reagents, which have been widely utilized in organic synthesis, can be generated by the reaction of TiX n (X = halogen, n = 3 or 4) with a reducing agent or, as more recently reported, from Cp 2 TiCl 2 (Cp = η 5 -cyclopenetadienyl) or Ti­(OR) 4 with an appropriate reductant. Thus, Cp 2 Ti­(III)Cl (and its dimer), Cp 2 TiPh, and Cp 2 Ti­(II)­(L) n (L = ligand) can be generated by reduction of Cp 2 TiCl 2 with Zn, Na­(Hg), Mg, or n -BuLi. , Furthermore, the reaction of Ti­(O- i -Pr) 4 or ClTi­(O- i -Pr) 3 with an alkyl Grignard or lithium reagent can generate a divalent titanium equivalent (η 2 -alkene)­Ti­(O- i -Pr) 2 . These reagents enable a variety of unique molecular transformations.…”