Syntheses and characterization of the edge-bridged open metallocenes M(C8H11)2 (C8H11 = cyclooctadienyl; M = Ti, V, Cr or Fe)†

Abstract

The reactions of two equivalents of the cyclooctadienyl anion with various divalent transition metal salts (M = Ti, V, Cr or Fe) led to the formation of the appropriate bis(cyclooctadienyl)metal complexes, isolable as crystalline compounds. Their constitutions have been established through NMR and mass spectroscopies, elemental analyses, and single crystal X-ray diffraction studies. As with the M(2,4-C₇H₁₁)₂ and M(6,6-dmch)₂ (C₇H₁₁ = dimethylpentadienyl; dmch = dimethylcyclohexadienyl) complexes, the titanium and vanadium compounds adopt low spin configurations, thereby differing from their metallocene analogs. The structures observed for these complexes in the solid state are similar to those of the M(2,4-C₇H₁₁)₂ complexes. The low spin titanium complex also forms a mono(ligand) adduct with CO, although the binding appears noticeably weak due to the steric influence of the edge bridge.