The First Linear, Homoleptic Triple-Decker Sandwich Complex of an f-Element: A Molecular Model for Organolanthanide Nanowires

Abstract

The first structurally authenticated linear, homoleptic triple-decker sandwich complex of an f-element, (η8-COT′′)Nd(μ-η8:η8-COT′′)Nd(η8-COT′′) (2; COT′′ = [C8H6(SiMe3)2-1,4]2−) has become available through a rather unexpected synthetic pathway. Treatment of [Li(THF)4][Nd(COT′′)2] (1) with anhydrous cobalt(II) chloride (molar ratio ca. 2:1) in a toluene suspension afforded 2 in 72% isolated yield. The most notable structural feature of 2 is the near-linear arrangement of the COT′′ rings with (ring centroid)−Nd−(ring centroid) angles of 176.1 and 175.6°, respectively, and a Nd−(ring centroid)−Nd angle of 177.9°, making the title compound the first true molecular model for lanthanide-based nanowires.

Five different types of η8-cyclooctatetraenyl-lanthanide half-sandwich complexes from one ligand set, including a “giant neodymium wheel”

“…The average Nd−C(COT) distances range from 2.826 Å to 2.835 Å, similar to those found in (in the triple-decker sandwich-complex (η 8 -COT″)Nd((µη 8 :η 8 -COT″)Nd(η 8 -COT″) with a range from 2.815(3) to 2.922(3) Å 33. Ellipsoids of the heavier atoms with 50% probability, H atoms and peripheral C atoms of the cyclohexyl groups omitted for clarity.…”

Lanthanide(III) Sandwich and Half‐Sandwich Complexes with Bulky Cyclooctatetraenyl Ligands: Synthesis, Structures, and Magnetic Properties

“…Most of them have been isolated as crystalline salts with either [Li(THF) 4 ] + or [Li(DME) 3 ] + , although differently solvated species such as [Li(THF)(DME)Dy(COT′′) 2 ] and Li(DME)[Tb(COT′′) 2 ] have also been described. As mentioned above, these complexes are key precursors for the preparation of the homoleptic triple‐decker sandwich complexes [Ln 2 (COT′′) 3 ] . To extend the number of available starting materials, we prepared three [Ln(COT′′) 2 ] – complexes as solvates with three different donor solvents, namely THF, DME (1,2‐dimethoxyethane), and TMEDA ( N , N , N′ , N′ ‐tetramethylethylenediamine), as illustrated in Scheme .…”

“…As mentioned above, these complexes are key precursors for the preparation of the homoleptic triple-decker sandwich complexes [Ln 2 (COT′′) 3 ]. [38][39][40][41] To extend the number of available starting materials, we prepared three [Ln(COT′′) 2 ]complexes as solvates with three different donor solvents, namely THF, DME (1,2dimethoxyethane), and TMEDA (N,N,N′,N′-tetramethylethylenediamine), as illustrated in Scheme 1. The lithium reagent Li 2 (COT′′) was prepared from the cyclooctatriene derivative 1,4-C 8 H 6 (SiMe 3 ) 2 by reaction with 2 equiv.…”

“…These anionic species are interesting precursors as they can undergo clean redox reactions with anhydrous CoCl 2 with the formation of the linear, homoleptic triple‐decker sandwich complexes [Ln 2 (COT′′) 3 ]. Thus far, binuclear [Ln 2 (COT′′) 3 ] complexes have been reported for Ln = Nd, Gd, Dy, Ho, and Er . Single‐ion magnet (SIM) or SMM behavior has been reported for various Ln(COT′′) compounds of these types, including, for example, [Li(THF)(DME)][Dy(COT′′) 2 ], [Li(DME) 3 ][Nd(COT′′) 2 ], [Li(DME) 3 ][Dy(COT′′) 2 ], [Ln 2 (COT′′) 3 ] (Ln = Gd, Dy), [Er 2 (COT′′) 3 ], and [Cp*Ln(COT)] (Ln = Dy, Ho, Er; Cp* = η 5 ‐pentamethylcyclopentadienyl) .…”

“…Thus far, binuclear [Ln 2 (COT′′) 3 ] complexes have been reported for Ln = Nd, Gd, Dy, Ho, and Er. [38][39][40][41] Single-ion magnet (SIM) or SMM behavior has been reported for various Ln(COT′′) compounds of these types, including, for example, [Li(THF)(DME)][Dy (COT′′) 2 ], [42] [Li(DME) 3 ][Nd(COT′′) 2 ], [37] [Li(DME) 3 ][Dy (COT′′) 2 ], [40] [Ln 2 (COT′′) 3 ] (Ln = Gd, Dy), [40] [Er 2 (COT′′) 3 ], [41] and [Cp*Ln(COT)] (Ln = Dy, Ho, Er; Cp* = η 5 -pentamethylcyclopentadienyl). [43] In the last case, the corresponding Tb and Tm complexes did not show slow relaxation behavior.…”