The Archetypal Homoleptic Lanthanide Quadruple‐Decker—Synthesis, Mechanistic Studies, and Quantum Chemical Investigations

Abstract

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.

Silole and germole complexes of lanthanum and cerium

“…). 11 The chemistry of aromatic group 14 dianionic metalloles has reemerged as a topic of interest in the recent years. 12 In particular, silole and germole dianions have gained attentions not only due to the potentially aromatic character but also the electronic features acting as ligand.…”

“…Recently, our group disclosed the missing structure of the homoleptic mixed-valence tetra-decker species [(η 8 -COT TIPS )Sm(μ-η 8 :η 8 -COT TIPS )Sm(μ-η 8 :η 8 -COT TIPS )Sm(η 8 -COT TIPS )] (COT TIPS = 1,4-Si i Pr 3 C 8 H 6 2− ). 11…”

Heteroleptic Rare-Earth Tris(metallocenes) Containing a Dibenzocyclooctatetraene Dianion

“…The addition of two electrons generates a remarkably planar and aromatic ligand, (COT) 2– , in which its large size, dianionic nature, and ability to occupy several metal coordination sites have resulted in widespread use for the organometallic synthesis of both d - and f-block compounds. − The arguably most famous organoactinide complex is uranocene, U­(COT) 2 , albeit lanthanide variants comprising the bare or functionalized COT ligand have more recently garnered vast attention for their bonding situation and physical properties. , The added stability engendered by the large number of coordination sites blocked by the (COT) 2– ligand affords a synthon which has been used to access complexes that feature heteroleptic ligand scaffolds. , The utility of the (COT) 2– ligand surpasses that of organometallic chemistry; in fact, the implementation of prolate Er III ions gave rise to the highest blocking erbium-based single-molecule magnets (SMMs), due to the equatorial ligand field imposed by the COT-based ligands. − The modular COT scaffold allows for substitution to alter the steric bulk and solubility of the ligand. Thus, numerous derivatives with substituents varying from trimethylsilyl to cycloalkyl have been devised and employed in organometallic synthesis. − Various functionalized COT ligands (Figure ) have been shown to be instrumental in attaining unique geometries such as double-, , triple-, , and quadruple-decker complexes …”

“…11−19 Various functionalized COT ligands (Figure 1) have been shown to be instrumental in attaining unique geometries such as double-, 20,21 triple-, 14,22 and quadruple-decker complexes. 19 Relative to the outlined COT variants, larger arenecontaining COT ligands have been underexplored. 23 A remarkable arene-functionalized COT derivative, dibenzocyclooctatetraene (dbCOT), 24,25 features two fused benzo moieties on a central COT ring.…”

A homoleptic tris(diphosphacyclobutadiene) tripledecker sandwich complex

“…5 In contrast, a variety of rare earth cyclooctatetraenyl tripledeckers were reported by the groups of Edelmann and Murugusu (type C ), 6 and even a homoleptic quadruple-decker of samarium has been reported very recently. 7 In addition, lanthanoid and actinoid cyclobutadiene complexes are currently attracting considerable attention due their desirable single-molecule magnet (SMM) properties (among other reasons). 8,9 However, to the best of our knowledge homoleptic cyclobutadiene complexes of the f-elements are elusive although particularly favourable SMM properties were predicted for such species.…”