Half-open-titanocene chemistry: Coupling reactions of pentadienyl ligands with carbon-nitrogen and carbon-oxygen multiple bonds

Article abstract of DOI:10.1021/om00046a015

The reactions of Ti(C₅H₅)(2,4-C₇H₁₁)(PEt₃) (C₇H₁₁ = dimethylpentadienyl) with imines, ketones, and aryl isocyanides have been studied. In each case, the PEt₃ ligand is lost. In the reaction with benzylidenemethylamine, spectroscopic data indicate that coupling of the imine with one end of the 2,4-C₇H₁₁ ligand has occurred. With acetone or 3-pentanone, 2 equiv is incorporated, leading to couplings with each end of the open dienyl ligand. A single-crystal X-ray diffraction study has been carried out for the latter. The space group is P2₁/c with a = 11.467 (3) ?, b = 7.647 (2) ?, c = 23.981 (7) ?, β = 92.11 (3)°, and V = 2101.3 ?³ for Z = 4. The structure was refined to discrepancy indices of R = 0.042 and R_w = 0.042 and revealed σ-allyl coordination as well as evidence for π-alkoxide donation. The reactions with RNC (R = C₆H₅, p-CH₃C₆H₄, p-C₂H₅C₆H₄) were found to lead to the incorporation of 4 equiv of RNC. In each case, two of the isocyanides have, with the pentadienyl ligand, formed a coordinated diazabutadiene ligand and a seven-carbon-atom ring, while the other two have formed an unusual indole which is attached to the former pentadienyl ligand and to an amide which is coordinated to the metal center. For the p-C₂H₅C₆H₄NC product, the space group is P1 with a = 10.858 (11) ?, b = 11.103 (5) ?, c = 17.552 (8) ?, α = 90.35 (3)°, β = 96.80 (3)°, γ = 104.28 (6)°, and V = 2034.8 ?³ for Z = 2. The structure was refined to discrepancy indices R = 0.057 and R_w = 0.059.