Charge transfer effects on the paramagnetic properties of the [M(C8H8)2] and M(C5H5)(C8H8); M = Ti, Zr, Hf and Th, complexes

A systematic study of a series of (19e) [M(COT)2]n, (n = −1 for Th and n = +1 for Ti, Zr, Hf) and (17e) MCpCOT, where Cp and COT represent cyclopentadienyl [C5H5]− and cyclooctatetraene [C8H8]−2, respectively, has been performed using relativistic density functional theory with the two components ZORA Hamiltonian for the inclusion of scalar and spin–orbit effects. The EPR parameters were obtained as second order properties employing the EPR/NMR algorithms with an inclusion of spin–orbit coupling. The obtained g   tensor values are in good agreement with the experimental results and the calculations reveals that each ground state in all systems are nonbonding and of mostly of dz2 character. There is a low spin density at protons site resulting from a direct delocalization of the unpaired electron spin on the 1s orbitals.

Graphical abstractWe found that the positive spin density at the (COT) protons is due to the direct delocalization of the unpaired electron spin on the 1s hydrogen orbitals of (COT) fragment. It is noteworthy that this positive value increases in the group for the M(COT)2 systems, although the metal-proton distance is smaller in Ti and increases for the other heavier elements.Figure optionsDownload full-size imageDownload as PowerPoint slide