Unequivocal assignments of C(2,5) and C(3,4) on the cyclopentadienyl ring of Cp2Fe, CpCr(CO)(2)(NO), and CpW(CO)(3)(CH3) bearing an electron-donating or electron-withdrawing substituent via resonance in C-13 NMR spectra

摘要

Complexes (NO)(2)(X)Cr(eta(5)-C5H4NHCOOCH2C6H5) (X = Cl 2; I, 3; CH3, 4) were synthesized. A reaction between (CO)(3)(CH3)W(eta(5)-C5H4COY) 8 (Y = OH) and PCl5 yielded 9 (Y = Cl). 9 was converted to 10 (Y = N-3) with NaN3. 10 underwent Curtius rearrangement in the presence of CH3OH to give (CO)(3)(CH3) W(eta(5)-C5H4NHCOOCH3) 7. Reaction of 9 with aniline led to carboxamide 11 (Y = NHC6H5). We observed that C(3,4) resonates at a lower field than C(2,5) in all Cp(M) (M = W. Fe) metallocene derivatives bearing either an electron-donating substituent or an electron-withdrawing substituent via resonance. The hypothesis to elucidate these data assignments was proposed. The electron density distribution in the cyclopentadienyl ring was discussed on the basis of C-13 NMR data and those of 5-7, 10, 11, 13, 16, and 17 were compared with calculations using the density functional B3LYP exchange-correlation method based on their X-ray structural data. (C) 2015 Elsevier B.V. All rights reserved.