A Trinuclear Gadolinium Cluster with a Three-Center One-Electron Bond and an = 11 Ground State.

The recent discovery of metal-metal bonding and valence delocalization in the dilanthanide complexes (Cp)LnI (Cp = pentaisopropylcyclopentadienyl; Ln = Y, Gd, Tb, Dy) opened up the prospect of harnessing the 4f5d 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)LnHI (, Ln = Y, Gd), which were synthesized via potassium graphite reduction of the trivalent clusters (Cp)LnHI. Structural, computational, and spectroscopic analyses support valence delocalization in resulting from a three-center, one-electron σ bond formed from the 4d and 5d orbitals on Y and Gd, respectively. Dc magnetic susceptibility data obtained for 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 = 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 = 168(1) cm determined for is only the second largest coupling constant characterized to date for a molecular lanthanide compound.