摘要:
A comparative investigation on five different Cp2Ti(diselenolene) complexes, i.e. Cp2Ti(Se(2)C(2)Z(2)) (Z=-CO2Me), Cp2Ti(Se(2)C(2)Z(CF3), CP2Ti(bds) (bds = 1,2-benzene-diselenato), CP2Ti(dsit) (dsit = 1,3-dithiole-2-thione-4,5-diselenato) and CP2Ti(ddds) (ddds = 5,6-dihydro- 1,4-dithiine-2,3-diselenato) is performed based on structural and variable-temperature NMR data. Preparation Of Cp2Ti[Se(2)C(2)Z(CF3)] involves the reaction of CP2TiSe5 with an excess of methyl-4,4,4-trifluorotetrolate while CP2Ti(bds) is obtained from the bds(2-) diselenolate and Cp2TiCl2. Their X-ray crystal structures have been determined, showing that Cp2Ti(bds) is not isostructural with the sulfur analog Cp2Ti(bdt). Similarly the structures Of Cp2Ti(dsit) and Cp2Ti(Se(2)C(2)Z(2)) were also determined from single crystal X-ray diffraction. All complexes exhibit a strong folding of the metallacycle along the Se center dot center dot center dot Se hinge, ranking from 47.8 degrees in Cp2Ti (Se(2)C(2)Z(2)) to 52.3 degrees in CP2Ti(ddds). VT NMR investigations on CP2Ti[Se(2)C(2)Z(CF3)] and Cp2Ti(ddds), complementing earlier results on the other complexes, show that the largest activation energies and associated folding angles are observed with the most electron rich diselenolenes (ddds, bds), a behavior closely related to that observed earlier in dithiolene complexes. (c) 2007 Elsevier B.V. All rights reserved.