Synthesis, structures and magnetic properties of [(η9-C9H9)Ln(η8-C8H8)] super sandwich complexes

Abstract

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.

Size‐Controlled Hapticity Switching in [Ln(C9H9)(C8H8)] Sandwiches

“…In this work, the bis‐Cnt [Ln(Cnt) 2 ] divalent complexes of Ln=Sm, Eu, Tm and Yb have been obtained in good yields through the use of a mixture of two isomers of the Cnt potassium salt: the cis‐cis‐cis‐cis and the cis‐cis‐cis‐trans forms (Scheme 1). A step further was the use of this mono‐anionic ligand in combination with the dianionic Cot ligand to form neutral sandwiches with linear geometry [13] . In this series, the geometry is particularly well adapted for maximizing the anisotropy of the erbium complex and, indeed, the latter was reported to present interesting SMM properties, confirming the adapted Er‐Cnt/Cot pair anisotropy.…”

Chelating Guanidinates for Dysprosium(III) Single‐Molecule Magnets†

“…[ 7‐8 ] The first electron delocalized organometallic SMM is (Cp*)Er(COT) reported in 2011. [ 9 ] From then on, the SMMs based on cyclopentadienyl (Cp – ) [ 10 ] and other related cyclic ligands were explored, such as [C 7 H 7 ] 3– , [ 11 ] [C 8 H 8 ] 2– , [ 12 ] [C 9 H 9 ] – , [ 13 ] [C 8 H 6 ] 2– , [ 14 ] [C 4 P] – , [ 15 ] and [C 2 B 9 H 11 ] 2– , [ 16 ] etc ., so as to achieve high performance SMMs. However, some of them such as [C 8 H 8 ] 2– and [C 9 H 9 ] – and some inorganic chelating ligands, [ 17 ] cannot impose the suitable crystal field on Dy 3+ because the larger coordination area.…”

Bis‐Cyclooctatetraenyl Thulium(II): Highly Reducing Lanthanide Sandwich Single‐Molecule Magnets

“…These ligands are indeed well adapted to access original and useful geometries that are more difficult to obtain with other coordination compounds [1b] . The use of a larger aromatic ligand, the cyclononatetraenyl (Cnt) ligand, recently led to the formation of perfectly linear neutral complexes of divalent lanthanides (Ln II ) [3] and to heteroleptic complexes bearing both the Cot and Cnt ligands [4] . The synthetic description and structural analyses of such compounds remain very challenging in organometallic chemistry but the principal purpose of their reports has moved in the last years from reactivity, redox [5] or polymerization studies to attractive magnetic properties.…”

“…[1b] Theu se of al arger aromatic ligand, the cyclononatetraenyl (Cnt) ligand, recently led to the formation of perfectly linear neutral complexes of divalent lanthanides (Ln II ) [3] and to heteroleptic complexes bearing both the Cot and Cnt ligands. [4] Thes ynthetic description and structural analyses of such compounds remain very challenging in organometallic chemistry but the principal purpose of their reports has moved in the last years from reactivity,redox [5] or polymerization studies to attractive magnetic properties.A s such, organolanthanide complexes with spectacular magnetic properties were until very recently [6] reserved for trivalent lanthanides but not divalent ones.…”