Chiral Bis(η⁵:η¹-pentafulvene)titanium Complexes

The series of bis(pentafulvene)titanium complexes (η⁶-C₅H₄CR₂)₂Ti (CR₂ = C(p-tol)₂ (3), adamantyl (4)) and their corresponding bis(benzofulvene) derivatives (η⁶-C₉H₆CR₂)₂Ti (CR₂ = C(p-tol)₂ (7), adamantyl (8)) have been synthesized by reaction of TiCl₃·3THF with the pentafulvene ligands (2 equiv) and magnesium as reducing agent (1.5 equiv). The bis(fulvene) complexes 7 and 8 have been obtained as diastereomerically pure compounds. All complexes have been characterized by spectroscopy and by single-crystal X-ray diffraction. The bonding situation is best described as a π-η⁵:σ-η¹ coordination mode. The bis(fulvene) complex 3 is approximately C₂ symmetric, whereas 7 crystallizes as a conglomerate in the monoclinic space group P2₁ and one of the enantiomers was identified as a (S,pS,pR) stereoisomer showing C₁ symmetry. The adamantyl benzofulvene complex 8 crystallizes in the monoclinic space group P2₁/c; both benzofulvene ligands are coordinated as optical antipodes, and a (S,pS,pR)/(R,pR,pS) configuration is found in the solid state. Reaction of 3 and 7 with HCl/Et₂O leads to the corresponding bis(cyclopentadienyl)titanium chlorides (η⁵-C₅H₄−CHR₂)₂TiCl₂ (R = p-tol (9)) and the bis(indenyltitanium) derivative (η⁵-C₉H₆−CHR₂)₂TiCl₂ (R = p-tol₂ (10)).