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

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 crystalli ne compounds. Their constitutions have been established through NMR and mas s 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=dimethylpent adienyl; dmch=dimethylcyclohexadienyl) complexes, the titanium and vanadium compounds adopt low spin configurations, thereby differing from their meta llocene analogs. The structures observed for these complexes in the solid s tate are similar to those of the M(2,4-C7H11)(2) complexes. The low spin ti tanium complex also forms a mono(ligand) adduct with CO, although the bindi ng appears noticeably weak due to the steric influence of the edge bridge.