Thermal Decomposition of Aryl- and Benzyl-dicyclopentadienyltitanium(III) Compounds and their Dinitrogen Complexes

The compounds Cp2TiR and their dinitrogen complexes (Cp2TiR)2N2 (R = benzyl, aryl) were investigated by differential thermal analysis and analysis of the products of thermolysis. The following stability sequences were found: for Cp2TiR: R = C6H5 ≈ m-CH3C6H4 ≈ p-CH3C6H4 < CH2C6H5 < o-CH3C6H4 ≈ C6F5 < 2,6-(CH3)2C6H3 ≈ 2,4,6-(CH3)3C6H2; for (Cp2TiR)2N2: R = o-CH3C6H4 < C6F5 < CH2C6H5 < C6H5 ≈ m-CH3C6H4 ≈ p-CH3C6H4. The complexes (Cp2TiR)2N2 lose the complexed N2 molecule with formation of Cp2TiR. The compounds Cp2TiR (R = C6F5 being an exception) decompose on heating with formation of RH (essentially quantitative) and a Ti-containing residue of complex nature. The Cp2Ti structure is lost. Experiments using deuterated ligands and solvents show the thermal decomposition to be intermolecular in aromatic solutions. An explanation of the observed variation of the thermal stabilities of the compounds Cp2TiR and (Cp2TiR)2N2 is given.