Sandwich complexes are an indispensable part of organometallic chemistry, which is becoming increasingly important in the field of lanthanide-based single molecule magnets. Herein, a fundamental class of pure sandwich complexes, [(η 9 -C 9 H 9 )Ln(η 8 -C 8 H 8 )] (Ln=Nd, Sm, Dy, Er), is reported. These neutral and sandwiched lanthanide compounds exclusively contain fully π-coordinated coplanar eight and nine membered CH rings. The magnetic properties of these compounds are investigated, leading to the observation of slow relaxation of the magnetization, including open hysteresis loops up to 10 K for the Er(III) analogue. Fast relaxation of the magnetization is likewise observed near zero field, a highly important characteristic for quantum information processing schemes. Our synthetic strategy is straightforward and utilizes the reaction of [(η 8 -C 8 H 8 )LnI(thf) n ] complexes with [K(C 9 H 9 )]. Although all compounds are fully characterized, structural details of the title compounds can also be deduced by Raman spectroscopy only.

f-element sandwich complexes bearing a η5-plumbole ligand are reported. Quantum chemical calculations suggest that this ligand retains its aromaticity upon coordination. The Er complexes show SMM behavior including magnetic hysteresis.

Novel lanthanide multi-decker complexes were established utilizing dianionic group 14 metallole ligands. The dimensionality of the multidecker species increases from a dimeric structure to 2D depending on the lanthanide ion and the metallole ligand.

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Reduction of [Sm III (COT 1,4-SiiPr3 )(BH 4 )(thf)] (COT 1,4-SiiPr3 = 1,4-( i Pr 3 Si) 3 C 8 H 6 ) with KC 8 resulted in [Sm III/II/III (COT 1,4-SiiPr3 ) 4 ], the first example of a homoleptic lanthanide quadruple-decker. As indicated by an analysis of the bond metrics in the solid-state, the inner Sm ion is present in the divalent oxidation state, while the outer ones are trivalent. This observation could be confirmed by quantum chemical calculations. Mechanistic studies revealed not only insight into possible formation pathways of [Sm III/II/III (COT 1,4-SiiPr3 ) 4 ] but also resulted in the transformation to other mixed metal sandwich complexes with unique structural properties. These are the 1D-polymeric chain structured [KSm III (COT 1,4-SiiPr3 )] n and the hexametallic species [(tol)K(COT 1,4-SiiPr3 )Sm II (COT 1,4- SiiPr3)K] 2 which were initially envisioned as possible building blocks as part of different retrosynthetically guided pathways that we developed.