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The formation, crystal and molecular structure of (η5-pentamethylcyclopentadienyl)(η7-cycloheptatrienyl)titanium and (η5-pentamethylcyclopentadienyl)(η8-cyclooctatetraene)titanium

1985; Elsevier BV; Volume: 297; Issue: 3 Linguagem: Inglês

10.1016/0022-328x(85)80430-7

1872-8561

Larry B. Kool, Marvin D. Rausch, Robin D. Rogers,

Rare-earth and actinide compounds

(η5-C5Me5)(η8-C8H8)Ti was prepared in 34% yield from a reaction between (η5-C5Me5)TiCl3 and K2C8H8 in THF solution, and in 31% yield from reduction of (η5-C5Me5)TiCl3 in THF solution by magnesium metal in the presence of cyclooctatetraene. The latter synthesis could be extended to the synthesis of (η5-C5H5)(η8-C8H8)Ti in 38% yield. Reduction of (η5-C5Me5TiCl3 in THF solution by metallic magnesium in the presence of cycloheptatriene produced (η5-C5Me5)(η7-C7H7)Ti in 68% yield. The structure of (η5-C5Me5)(η8-C8H8)Ti, at room temperature, was examined. This compound crystallizes in the orthorhombic space group Pnma with unit cell constants, a 9.946(7), b 13.597(4), c 11.513(9) Å and D(calc) 1.23 g cm−3 for Z = 4. Full matrix least-squares refinement using 915 independent observed reflections resulted in a final R value of 0.032. The titanium atom is located on a crystallographic mirror plane which bisects the two aromatic rings. The eight membered ring is disordered into two orientations. The average TiC(η8) and TiC(η5) distances are 2.34(2) and 2.338(5) Å, respectively. A low temperature (−90°C) X-ray diffraction study of (η5-C5Me5)(η7-C7H7)Ti resolved the disorder problem found for the C8H8 analogue. (η5-C5Me5)(η7-C7H7)Ti crystallizes in the orthorhombic space group Pnma with a 10.327(2), b 12.441(3), c 11.025(1) Å (at −90±2°C) and D(calc) 1.29 g cm−3 for Z = 4. A final R value of 0.048 was obtained from full matrix least-squares refinement based on 1143 independent observed reflections. The titanium atom resides on a crystallographic mirror plane which bisects the two aromatic rings. The TiC(η7) distances average 2.21(1) Å, the TiC(η5) separations average 2.32(1) Å, and the Cent(η5)TiCent(η7) angle is 176.2°.