Low‐Valent Titanium–Pentafulvene Complexes — Formation of Dinuclear Titanium–Nitrogen Complexes

Sodium amalgam reduction of [(η 5 ‐C 5 Me 5 )TiCl 3 ] ( 1 ) in the presence of the pentafulvenes {C 5 H 4 =CR 2 , R: p ‐tol ( 2 ), p ‐FPh ( 3 ), CR 2 : adamantyl ( 4 )} under nitrogen smoothly produces dark green or dark blue dinuclear low‐valent titanium complexes [{(η 5 ‐C 5 Me 5 )Ti(η 6 ‐C 5 H 4 =CR 2 )} 2 (μ 2 ,η 1 ,η 1 ‐N 2 )] {R: p ‐tol ( 6 ), p ‐FPh ( 7 ), CR 2 : adamantyl ( 8 )}, characterized by a bridging end‐on coordinated dinitrogen ligand, in high yield. In the same way, the nitrogen‐free, low‐coordinated complex [(η 5 ‐C 5 Me 5 )Ti(η 6 ‐C 9 H 6 =C( p ‐tol) 2 )] ( 10 ) is obtained by using the more sterically demanding benzofulvene C 9 H 6 =C( p ‐tol) 2 ( 5 ) instead of 2 – 4 . The solid‐state structures of the dinitrogen compounds reveal weakly activated end‐on bound N 2 ligands with identical N–N distances of 1.160(3) Å ( 6 ) and 1.160(5) Å ( 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, 69451 Weinheim, Germany, 2005)