Reactivity Studies of a Bis(π-η5:σ-η1-benzofulvene)titanium Complex Including Simultaneous N-H and C(sp2)-H Activation of Dibenzylamine

The improved multigram synthesis of the bis(pi-eta(5):sigma-eta(1)-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-C-q,(exo) bond(s) were found to diastereoselectively yield complexes 2-5. Compound 1 reacts with molecular hydrogen to afford the formal H-2 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 C(q,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(sp(2))-H (in position y to 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 eta(5) coordination mode. The one exception is complex 8, in which one indenyl ligand shows signs for a haptotropic shift to eta(3).