The Solution Structures and Dynamics and the Solid-State Structures of Substituted Cyclopentadienyltitanium(IV) Trifluorides
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- 作者：Franc Perdih ; Andrej Pevec ; Sa
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- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：September 18, 2006
- 年：2006
- 卷：45
- 期：19
- 页码：7915 - 7921
- 全文大小：140K
- 年卷期：v.45,no.19(September 18, 2006)
- ISSN：1520-510X
文摘
Organotitanium fluorides (C5Me4R)TiF3 (R = H, Me, Et) sublimate with formation of crystalline dimers. From solution,we obtained crystals of dimers and tetramers. The tetramer [{(C5Me5)TiF3}4] irreversibly dissociates in the solidstate to dimers (
H = 8.33 kcal mol-1). The variable-temperature 1H and 19F NMR spectroscopy measurementsof the toluene-d8 solution of [{(C5Me5)TiF3}2] revealed at 202 K one monomeric, two dimeric (with C2h and Cssymmetry), two tetrameric (with D2 and C2v symmetry), and two trimeric (both C2 symmetry) molecules. With theincrease in temperature and dilution of the solution, the composition of the solution shifts to the smaller molecules.The thermodynamic and activation parameters for the reversible dissociation of dimers to monomers in the solutionare H = 9.2 kcal mol-1, S = 24.2 cal mol-1 K-1, H
= 12.2 kcal mol-1, S = 9.7 cal mol-1 K-1. Thedissociation path with a weakly double-bridged transition-state dimer was proposed. The thermodynamic parametersfor the reversible dissociation of the C2v tetramer to the dimers in solution are H = 7.9 kcal mol-1 and S =26.8 cal mol-1 K-1. From both tetramers, the D2 molecule is 0.34(5) kcal mol-1 lower in enthalpy and 6.5(5) calmol-1 K-1 lower in entropy than the C2v molecule. The structures of both trimers were proposed. The low-temperature19F NMR spectra of the CDCl3 solution of [{(C5Me5)TiF3}2] are consistent with equilibria of a monomer, two dimers(with C2h and Cs symmetry), and a trimer. The vapor pressure osmometric molecular mass determination of CDCl3solution of [{(C5Me5)TiF3}2] at 302 K is consistent with the equilibrium of the dimer and the monomer.
H = 8.33 kcal mol-1). The variable-temperature 1H and 19F NMR spectroscopy measurementsof the toluene-d8 solution of [{(C5Me5)TiF3}2] revealed at 202 K one monomeric, two dimeric (with C2h and Cssymmetry), two tetrameric (with D2 and C2v symmetry), and two trimeric (both C2 symmetry) molecules. With theincrease in temperature and dilution of the solution, the composition of the solution shifts to the smaller molecules.The thermodynamic and activation parameters for the reversible dissociation of dimers to monomers in the solutionare H = 9.2 kcal mol-1, S = 24.2 cal mol-1 K-1, H = 12.2 kcal mol-1, S = 9.7 cal mol-1 K-1. Thedissociation path with a weakly double-bridged transition-state dimer was proposed. The thermodynamic parametersfor the reversible dissociation of the C2v tetramer to the dimers in solution are H = 7.9 kcal mol-1 and S =26.8 cal mol-1 K-1. From both tetramers, the D2 molecule is 0.34(5) kcal mol-1 lower in enthalpy and 6.5(5) calmol-1 K-1 lower in entropy than the C2v molecule. The structures of both trimers were proposed. The low-temperature19F NMR spectra of the CDCl3 solution of [{(C5Me5)TiF3}2] are consistent with equilibria of a monomer, two dimers(with C2h and Cs symmetry), and a trimer. The vapor pressure osmometric molecular mass determination of CDCl3solution of [{(C5Me5)TiF3}2] at 302 K is consistent with the equilibrium of the dimer and the monomer.