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ansa-metallocene derivatives XXXVI. Dimethylsilyl-bridged permethyl chromocene carbonyl complexes : syntheses, crystal structures and interconversion reactions

ansa-metallocene derivatives XXXVI. Dimethylsilyl-bridged permethyl chromocene carbonyl complexes : syntheses, crystal structures and interconversion reactions

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SCHAPER, Frank, Marcus RENTZSCH, Marc-Heinrich PROSENC, Ursula RIEF, Katrin SCHMIDT, Hans-Herbert BRINTZINGER, 1997. ansa-metallocene derivatives XXXVI. Dimethylsilyl-bridged permethyl chromocene carbonyl complexes : syntheses, crystal structures and interconversion reactions. In: Journal of Organometallic Chemistry. 534(1-2), pp. 67-79. ISSN 0022-328X

@article{Schaper1997ansa--23892, title={ansa-metallocene derivatives XXXVI. Dimethylsilyl-bridged permethyl chromocene carbonyl complexes : syntheses, crystal structures and interconversion reactions}, year={1997}, doi={10.1016/S0022-328X(96)06895-7}, number={1-2}, volume={534}, issn={0022-328X}, journal={Journal of Organometallic Chemistry}, pages={67--79}, author={Schaper, Frank and Rentzsch, Marcus and Prosenc, Marc-Heinrich and Rief, Ursula and Schmidt, Katrin and Brintzinger, Hans-Herbert} }

deposit-license Prosenc, Marc-Heinrich Schaper, Frank Prosenc, Marc-Heinrich 2013-08-05T08:57:53Z eng Schmidt, Katrin Schmidt, Katrin Rief, Ursula Rief, Ursula 1997 Journal of Organometallic Chemistry ; 534 (1997), 1-2. - S. 67-79 2013-08-05T08:57:53Z The ring-bridged chromocene carbonyl complex Me<sub>2</sub>Si(C<sub>5</sub>Me<sub>4</sub>)<sub>2</sub>Cr(CO) 1 is obtained by reaction of Me<sub>2</sub>Si(C<sub>5</sub>Me<sub>4</sub>)<sub>2</sub>Li<sub>2</sub> with CrCl<sub>2</sub> · THF in the presence of CO. Reaction with CO transforms the monocarbonyl complex 1 to a dicarbonyl complex Me<sub>2</sub>Si(C<sub>5</sub>Me<sub>4</sub>)(C<sub>5</sub>(endo-3-H)(2-CH<sub>2</sub>)Me<sub>3</sub>)Cr(CO)<sub>2</sub>2; in this reaction, a hydrogen atom is shifted from one of the α-CH<sub>3</sub> groups to the adjacent β-position of a C<sub>5</sub> ring ligand. The rate of this reaction is first order in complex and CO concentration, with an activation enthalpy of H<sup>≠</sup> = 51 ± 3 kJ mol−1 and an activation entropy of S<sup>≠</sup> = 136 ± 10 J mol<sup>−1</sup> K<sup>−1</sup>. In toluene solution at 50°C, complex 2 isomerizes to Me<sub>2</sub>Si(C<sub>5</sub>Me<sub>4</sub>)(C<sub>5</sub>(exo-3-H)(2-CH<sub>2</sub>)Me<sub>3</sub>)Cr(CO)23, then to Me<sub>2</sub>Si(C<sub>5</sub>Me<sub>4</sub>)(C<sub>5</sub>(exo-1-H)(2-CH<sub>2</sub>)Me<sub>3</sub>)Cr(CO)24 and further to Me<sub>2</sub>Si(C<sub>5</sub>Me<sub>4</sub>)(C<sub>5</sub> (endo-5-H)(2-CH<sub>2</sub>)Me<sub>3</sub>)Cr(CO)<sub>2</sub>5. The kinetics of these isomerizations, which involve hydrogen migrations and ring rotation reactions, indicate monomolecular reactions. Possible reaction paths and transition states are discussed. The structures of complexes 1–5 were determined by <sup>1</sup>H NMR spectroscopy, those of 1, 2, 4 and 5 also by single-crystal X-ray diffraction. Complex 1: space group P2<sub>1</sub>/n, a = 13.257(7)Å, b = 10.186(5)Å, c = 14.739(7) Å, β = 90.89(4)°; V = 1990.1(7)Å<sup>3</sup>; Z = 4. Complex 2: space group Pbca, a = 8.699(3) Å, b = 14.713(6) Å, c = 32.801(14)Å; V = 4198(3)Å<sup>3</sup>; Z = 8. Complex 4: space group P2<sub>1</sub>, a = 9.497(2)Å, b = 9.895(3) Å, c = 11.371(2)Å, β = 103.919(8)°; V = 1037.1(4) Å<sup>3</sup>; Z = 2. Complex 5: space group P2<sub>1</sub>/c, a = 16.555(4)Å, b = 13.036(3)Å, c = 10.044(2)Å, β = 107.45(1)°; V = 2067.8(8)Å3; Z = 4. Brintzinger, Hans-Herbert Rentzsch, Marcus ansa-metallocene derivatives XXXVI. Dimethylsilyl-bridged permethyl chromocene carbonyl complexes : syntheses, crystal structures and interconversion reactions Rentzsch, Marcus Schaper, Frank Brintzinger, Hans-Herbert

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