Reactivity Studies of a Bis(π-ν5:σ-ν1-benzofulvene)titanium Complex including Simultaneous N-H and C(sp2)-H Activation of Dibenzylamine
Fischer M., Fitschen K., Schmidtmann M., Beckhaus R.
The improved multigram synthesis of the bis(π-ν5:σ-ν1-benzofulvene)titanium complex 1 is reported. On the basis of this, the follow-up chemistry of complex 1 was investigated and selective mono or double insertion reactions with ketones and nitriles into the polarized Ti-Cq,exo bond(s) were found to diastereoselectively yield complexes 2-5. Compound 1 reacts with molecular hydrogen to afford the formal H2 addition products 6a-c of the benzofulvene ligand precursor. The reactions of 1 with selected secondary N-methylamines yield the titanium bisamides 7a and 7b in which both former benzofulvene Cq,exo atoms are protonated. Finally, treatment of 1 with equimolar amounts of dibenzylamine selectively yields the titanaazapentacycle 8. Complex 8 is the result of an unprecedented and simultaneous N-H and C(sp2)-H (in position γto the nitrogen atom) activation reaction. Single-crystal X-ray diffraction analyses of the key complexes reveal that the indenyl ligands in 2, 4a, and 5 consistently show the ν5 coordination mode. The one exception is complex 8, in which one indenyl ligand shows signs for a haptotropic shift to ν3