A Trinuclear Gadolinium Cluster with a Three-Center One-Electron Bond and an <i>S</i> = 11 Ground State
K. Randall McClain, Hyunchul Kwon, Khetpakorn Chakarawet, Rizwan Nabi, Jon G. C. Kragskow, Nicholas F. Chilton, R. David Britt, Jeffrey R. Long, Benjamin G. Harvey
Abstract
High Resolution Image Download MS PowerPoint Slide The recent discovery of metal–metal bonding and valence delocalization in the dilanthanide complexes (Cp iPr5 ) 2 Ln 2 I 3 (Cp iPr5 = pentaisopropylcyclopentadienyl; Ln = Y, Gd, Tb, Dy) opened up the prospect of harnessing the 4f n 5d z 2 1 electron configurations of non-traditional divalent lanthanide ions to access molecules with novel bonding motifs and magnetism. Here, we report the trinuclear mixed-valence clusters (Cp iPr5 ) 3 Ln 3 H 3 I 2 ( 1-Ln, Ln = Y, Gd), which were synthesized via potassium graphite reduction of the trivalent clusters (Cp iPr5 ) 3 Ln 3 H 3 I 3 . Structural, computational, and spectroscopic analyses support valence delocalization in 1-Ln resulting from a three-center, one-electron σ bond formed from the 4d z 2 and 5d z 2 orbitals on Y and Gd, respectively. Dc magnetic susceptibility data obtained for 1-Gd reveal that valence delocalization engenders strong parallel alignment of the σ-bonding electron and the 4f electrons of each gadolinium center to afford a high-spin ground state of S = 11. Notably, this represents the first clear instance of metal–metal bonding in a molecular trilanthanide complex, and the large spin–spin exchange constant of J = 168(1) cm –1 determined for 1-Gd is only the second largest coupling constant characterized to date for a molecular lanthanide compound.