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

Abstract

Organometallic 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 [{(KL3 Ce)(μ-η6 :η6 -C7 H8 )}2 Ce] (3). The structure of 3 features a [Ce(C7 H8 )2 ] sandwich capped by [KL3 Ce] 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=O3 SCF3 ) yielded the CeIV complex, [CeL4 ] (2), showing that siloxide ligands can stabilize Ce in three oxidation states.