Reduction of a Cerium(III) Siloxide Complex To Afford a Quadruple‐Decker Arene‐Bridged Cerium(II) Sandwich

Abstract

AbstractOrganometallic multi‐decker sandwich complexes containing f‐elements remain rare, despite their attractive magnetic and electronic properties. The reduction of the CeIII siloxide complex, [KCeL4] (1; L=OSi(OtBu)3), with excess potassium in a THF/toluene mixture afforded a quadruple‐decker arene‐bridged complex, [K(2.2.2‐crypt)]2[{(KL3Ce)(μ‐η6:η6‐C7H8)}2Ce] (3). The structure of 3 features a [Ce(C7H8)2] sandwich capped by [KL3Ce] moieties with a linear arrangement of the Ce ions. Structural parameters, UV/Vis/NIR data, and DFT studies indicate the presence of CeII ions involved in δ bonding between the Ce cations and toluene dianions. Complex 3 is a rare lanthanide multi‐decker complex and the first containing non‐classical divalent lanthanide ions. Moreover, oxidation of 1 by AgOTf (OTf=O3SCF3) yielded the CeIV complex, [CeL4] (2), showing that siloxide ligands can stabilize Ce in three oxidation states.