The catalytic system [(Cp2TiCl)2]:LiAlH4 in aromatic solvents,Part II. Formation of η3-allyltitanocene derivatives in the presence of dienes — their structure and e.s.r. spectra

Summary The addition of dienes to the system (Cp₂TiCl)₂] LiAlH₄toluene changes the system so that the complex Cp₂TiAlH₄] is quantitatively formed instead of a titanocene hydride — aluminium hydride cluster. The complex Cp₂TiAlH₄] is further converted into ³-allyltitanocene derivatives (Cp₂TiA]) if the diene structure is suitable for formation of stable Cp₂TiA] compounds and if the equilibrium Cp₂TiAlH₄]+dieneCp₂TiA]+A1H₃ is shifted towards the formation of Cp₂TiA] by the excess of diene. All the compounds Cp₂TiA] exhibit high-resolution e.s.r. spectra at g=1.993, showing interaction of the unpaired electron with the cyclopentadienyl and ³-allyl protons. The e.s.r. spectra clearly reveal the presence of alkyl substituents atsyn-1,3-positions of ³-allyl ligand, and show a triplet of multiplets for (³-allyl)titanocene, doublets of multiplets for (1-alkyl-³-allyl)titanocenes and single multiplets for (1,3-dialkyl-³-allyl)-titanocenes. thermal isomerization of (1,3-dimethyl-³-allyl)-titanocene and (1-methyl-3-ethyl-³-allyl)titanocene, hitherto considered as the stable Cp₂TiA compounds, into (1-alkyl-³-allyl)titanocenes was confirmed by e.s.r. and electronic absorption spectroscopy as well as by chemical means.