Cycloheptatrienyl-Bridged Triple-Decker Complexes.

The first structurally characterized organometallic multidecker sandwich complexes featuring a cycloheptatrienyl ring (Cht, C 7 H 7 3- ) in the coordination sphere are presented. The synthesis of inverse sandwich complexes of the rare earth elements Y III and Er III with a bridging cycloheptatrienyl ligand of the type [(thf)(BH 4 ) 2 Ln III (μ-η 7 :η 7 -Cht)Ln III (BH 4 )(thf) 2 ] is described first. The subsequent introduction of the Cot TIPS ligand (Cot TIPS = 1,4-( i Pr 3 Si) 2 C 8 H 6 2- ) into the coordination sphere of the rare earth cations resulted in the isolation of unprecedented triple-decker compounds with the formula [(thf) 3 K{(η 8 -Cot TIPS )Ln III } 2 (μ-η 7 :η 7 -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 Er III congeners were investigated in detail, leading to the observation of antiferromagnetic coupling of the Er III cations and a blocking temperature of 13.5 K. The conversion of the Y III compound [(thf) 3 K{(η 8 -Cot TIPS )Y III } 2 (μ-η 7 :η 7 -Cht)] with [Y III (Cot)I(thf) 2 ] resulted in ligand rearrangement and the selective formation of the first triple-decker complex ([(η 8 -Cot TIPS Y III ) 2 (μ-η 8 :η 8 -Cot)]) featuring two Cot ligands with different substituents in its coordination sphere.