Multiple-Decker Sandwich Complexes of Lanthanide−1,3,5,7-Cyclooctatetraene [Lnn(C₈H₈)m] (Ln = Ce, Nd, Eu, Ho, and Yb); Localized Ionic Bonding Structure

Organometallic lanthanide complexes of Ln n (C 8 H 8 ) m (Ln = lanthanide metals of Ce, Nd, Eu, Ho, and Yb; C 8 H 8 = 1,3,5,7-cyclooctatetraene) were produced by a combination of laser vaporization and molecular beam methods. The complexes having ( n, m ) = ( n, n + 1) for n = 1−5 were prominently produced as magic numbers in the mass spectra. Using mass spectrometry, photoionization spectroscopy, and photoelectron spectroscopy, it is concluded that these magic-numbered complexes form multiple decker sandwich structures in which Ln atoms and C 8 H 8 molecules are alternately piled up. The obtained spectroscopic data show that these sandwich complexes are formed through ionic bonds and are charge transfer complexes, where the Ln atoms are multiply charged cations of Ln k + ( k = 2 and 3) and C 8 H 8 molecules are multiply charged anions.