Synthesis, Crystal Structure, EPR and DFT Studies, and Redox Properties of [2]Tetramethyldisilacobaltocenophane
摘要:
The first [2]silacobaltocehophane, [(Me2Si)(2)(eta(5)-C5H4)(2)Co] (1), was synthesized by dilithiation of 1,2-bis(cyclopentadienyl)-1,1,2,2-tetramethyldisilane with BuLi and subsequent reaction with [CoBr2(dme)]. EPR spectroscopic investigations of frozen pentane solutions of 1 at X-band showed a fully anisotropic g tensor (g(1) = 1.914, g(2) = 2.005, and g(3) = 2.084) with hyperfine couplings on all three components (A(1) = 145 MHz, A(2) = 67 MHz, and A(3) = 424 MHz). DFT studies using the B3LYP functional with its 20% exact exchange provide the best agreement with experiment and reproduce the g and A tensors well. Spin-orbit contributions to the isotropic coupling (A(PC)) and to the anisotropies (A(i)(dip,2)) were found to be significant. As was shown by cyclic voltammetry in THF, 1 is quasi-reversibly oxidized to the neutral cobaltocenium cation [(Me2Si)(2)(eta(5)-C5H4)(2)Co](+) (8) at a potential of E-1/2 degrees = -1.27 V (vs the Fc/Fc(+) couple) and quasi-reversibly reduced to the corresponding anion [(Me2Si)(2)(eta(5)-C5H4)(2)Co](-) (9) at E-1/2 degrees = -2.40 V. The preparative oxidation of 1 with 1 equiv of feffocenium hexafluorophosphate ([Fc][PF6]) provided the diamagnetic [PF6](-) salt of the cation 8 in high yields. The molecular structures of both complexes (1 and 8) were confirmed by X-ray diffraction analysis, and a significant decrease in molecular strain was depicted. DFT findings support the experiments.
Synthesis, Crystal Structure, EPR and DFT Studies, and Redox Properties of [2]Tetramethyldisilacobaltocenophane
摘要:
The first [2]silacobaltocehophane, [(Me2Si)(2)(eta(5)-C5H4)(2)Co] (1), was synthesized by dilithiation of 1,2-bis(cyclopentadienyl)-1,1,2,2-tetramethyldisilane with BuLi and subsequent reaction with [CoBr2(dme)]. EPR spectroscopic investigations of frozen pentane solutions of 1 at X-band showed a fully anisotropic g tensor (g(1) = 1.914, g(2) = 2.005, and g(3) = 2.084) with hyperfine couplings on all three components (A(1) = 145 MHz, A(2) = 67 MHz, and A(3) = 424 MHz). DFT studies using the B3LYP functional with its 20% exact exchange provide the best agreement with experiment and reproduce the g and A tensors well. Spin-orbit contributions to the isotropic coupling (A(PC)) and to the anisotropies (A(i)(dip,2)) were found to be significant. As was shown by cyclic voltammetry in THF, 1 is quasi-reversibly oxidized to the neutral cobaltocenium cation [(Me2Si)(2)(eta(5)-C5H4)(2)Co](+) (8) at a potential of E-1/2 degrees = -1.27 V (vs the Fc/Fc(+) couple) and quasi-reversibly reduced to the corresponding anion [(Me2Si)(2)(eta(5)-C5H4)(2)Co](-) (9) at E-1/2 degrees = -2.40 V. The preparative oxidation of 1 with 1 equiv of feffocenium hexafluorophosphate ([Fc][PF6]) provided the diamagnetic [PF6](-) salt of the cation 8 in high yields. The molecular structures of both complexes (1 and 8) were confirmed by X-ray diffraction analysis, and a significant decrease in molecular strain was depicted. DFT findings support the experiments.