Cycloheptatrienyl-Bridged Triple-Decker Complexes.

The first structurally characterized organometallic multidecker sandwich complexes featuring a cycloheptatrienyl ring (Cht, C7H73-) in the coordination sphere are presented. The synthesis of inverse sandwich complexes of the rare earth elements YIII and ErIII with a bridging cycloheptatrienyl ligand of the type [(thf)(BH4)2LnIII(μ-η7:η7-Cht)LnIII(BH4)(thf)2] is described first. The subsequent introduction of the CotTIPS ligand (CotTIPS = 1,4-(iPr3Si)2C8H62-) into the coordination sphere of the rare earth cations resulted in the isolation of unprecedented triple-decker compounds with the formula [(thf)3K{(η8-CotTIPS)LnIII}2(μ-η7:η7-Cht)], bearing a seven-membered aromatic carbon ring as a middle deck. These compounds are also the first examples of rare earth triple-decker complexes not bridged by a Cot derivative, based on purely carbon-based ligands. The magnetic properties of the respective ErIII congeners were investigated in detail, leading to the observation of antiferromagnetic coupling of the ErIII cations and a blocking temperature of 13.5 K. The conversion of the YIII compound [(thf)3K{(η8-CotTIPS)YIII}2(μ-η7:η7-Cht)] with [YIII(Cot)I(thf)2] resulted in ligand rearrangement and the selective formation of the first triple-decker complex ([(η8-CotTIPSYIII)2(μ-η8:η8-Cot)]) featuring two Cot ligands with different substituents in its coordination sphere.