Low-valent titanium-pentafulvene complexes - Formation of dinuclear titanium-nitrogen complexes

Article abstract of DOI:10.1002/ejic.200400938

Sodium amalgam reduction of [(η5-C₅Me₅)TiCl ₃] (1) in the presence of the pentafulvenes {C₅H ₄=CR₂, R: p-tol (2), p-FPh (3), CR₂: adamantyl (4)} under nitrogen smoothly produces dark green or dark blue dinuclear low-valent titanium complexes [{(η⁵-C₅Me ₅)Ti(η⁶-C₅H₄=CR ₂)}₂(μ₂,η¹, η¹-N₂)] {R: p-tol (6), p-FPh (7), CR₂: adamantyl (8)}, characterized by a bridging end-on coordinated dinitrogen ligand, in high yield. In the same way, the nitrogen-free, low-coordinated complex [(η⁵-C₅Me₅)Ti(η⁶- C₉H₆=C(p-tol)₂)] (10) is obtained by using the more sterically demanding benzofulvene C₉H₆=C(P-tol) ₂ (5) instead of 2-4. The solid-state structures of the dinitrogen compounds reveal weakly activated end-on bound N₂ ligands with identical N-N distances of 1.160(3) A (6) and 1.160(5) A (8). The dinitrogen complexes 6, 7 and 8 show diamagnetic behaviour, which allowed a complete NMR spectroscopic characterization. So a correlation between the situation in solution, measured by NMR, and in the solid state (X-ray diffraction) becomes possible and shows a congruent picture. A broad range of reactions can be imagined concerning the easily replaceable dinitrogen ligand as well as the known reactivity of fulvene ligands in complexes of early transition metals. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.