Homoleptic Rare-Earth-Metal Sandwiches with Dibenzo[a,e]cyclooctatetraene Dianions

Abstract

A family of rare-earth complexes [RE(III) = Y, La, Gd, Tb, Dy, and Er] with doubly reduced dibenzo[a,e]cyclooctatetraene (DBCOT) has been synthesized and structurally characterized. X-ray diffraction analysis confirms that all products of the [RE(DBCOT)(THF) 4 ][RE(DBCOT) 2 ] composition consist of the anionic sandwich [RE(DBCOT) 2 ] − and the cationic counterpart [RE(DBCOT)(THF) 4 ] + . Within the sandwich, two elongated π decks are slightly bent toward the metal center (avg. 7.3°) with a rotation angle of 35.9−37.6°. The RE(III) ion is entrapped between the central eight-membered rings of DBCOT 2− in a η 8 fashion.The trends in the RE−COT bond lengths are consistent with the variations of the ionic radii of RE(III) centers. The 1 H NMR spectra of the diamagnetic Y(III) and La(III) analogues illustrate the distinct solution behavior for the cationic and anionic parts in this series. Magnetic measurements for the Dy analogue reveal single-molecule magnetism, which was rationalized by considering the effect of crystal-field splitting for both building units analyzed by electronic structure calculations.

Ligand–Metal Complementarity in Rare-Earth and Actinide Chemistry

“…In their work, Ding, Zhu, and Zheng’s team presented a unique twist on the area by exploring the differences between 1,3-, 1,4-, and also 1,5-substituted analogues of the {C 8 H 6 -(SiMe 3 ) 2 } ligand on the SMM properties of Er III complexes . Rogachev, Shatruk, Petrukhina, and their team continued the COT sandwich complex theme but instead have focused on a benzannulated analogue, dibenzo­[ a , e ]­cyclooctatetraene (DBCOT), which forms charge-separated ion pairs, [RE­(DBCOT)­(THF) 4 ]­[RE­(DBCOT) 2 ] (RE = Y, La, Gd, Tb, Dy, Er) . The SMM properties of the Dy III analogue were explored and showed a complicated relaxation pathway due to the presence of structurally dissimilar anionic and cationic Dy III fragments within the complex …”

“…Rogachev, Shatruk, Petrukhina, and their team continued the COT sandwich complex theme but instead have focused on a benzannulated analogue, dibenzo­[ a , e ]­cyclooctatetraene (DBCOT), which forms charge-separated ion pairs, [RE­(DBCOT)­(THF) 4 ]­[RE­(DBCOT) 2 ] (RE = Y, La, Gd, Tb, Dy, Er) . The SMM properties of the Dy III analogue were explored and showed a complicated relaxation pathway due to the presence of structurally dissimilar anionic and cationic Dy III fragments within the complex …”