Isolation of +2 rare earth metal ions with three anionic carbocyclic rings: bimetallic bis(cyclopentadienyl) reduced arene complexes of La²⁺ and Ce²⁺ are four electron reductants

Abstract

A new option for stabilizing unusual Ln2+ ions has been identified in the reaction of (C5H4SiMe3)3Ln (Ln = La, Ce) with potassium graphite and 2.2.2-cryptand in benzene.

Reduction of a Cerium(III) Siloxide Complex To Afford a Quadruple‐Decker Arene‐Bridged Cerium(II) Sandwich

“…The mean C−C ring bond length (average 1.441(18) Å) of the coordinating toluene molecules in 3 is similar to those found in the related complexes containing doubly reduced benzene anions, [K(2.2.2‐crypt)] 2 [{La(Cp′) 2 } 2 (μ‐η 6 :η 6 ‐C 6 H 6 )] (average 1.453(5) Å) and [K(18c6)][La(Cp′′) 2 (C 6 H 6 )] (average 1.425(56) Å), and in the anion, [{La(Cp tt ) 2 } 2 (μ‐η 6 :η 6 ‐C 6 H 6 )] − (1.44(1) Å), formulated by Lappert and co‐workers as containing two La II ions and the benzene radical anion C 6 H 6 −. .…”

“…The spectrum features a broad, intense band centered at 582 nm ( ϵ ≈4600 L mol −1 cm −1 ) (see the Supporting Information). Similar features were found in previously reported mononuclear Ce II complexes (absorption maxima in the visible region between 500–650 nm, with related molar extinction coefficients between 4700–7000 L mol −1 cm −1 ), supporting the presence of Ce II in complex 3 …”

“…Formation of arene‐bridged Ln complexes of the general formula [{Ln(Cp′) 2 } 2 (μ‐η 6 :η 6 ‐arene)] 2− (Cp′=C 5 H 4 (SiMe 3 )) and [{Ln(Cp R ) 2 } 2 (μ‐η 6 :η 6 ‐arene)] 1− (Cp R =Cp′ or Cp tt =C 5 H 3 1,3(tBu) 2 ‐1,3 and arene=C 6 H 6 or C 7 H 8 ),, accompanied by loss of an anionic ligand (Cp′=C 5 H 4 (SiMe 3 )), from the reduction of trivalent lanthanides complexes (Ln(Cp R ) 3 ) in carbocyclic solvents was reported, but formation of multi‐decker complexes under these conditions was not observed previously. While assignment of the oxidation state in these systems was difficult, it should be noted that small variation in reaction conditions or in the substituents on the Cp ligand resulted in different products presenting different degrees of reduction of the lanthanide ion and of the bridging arene (2− or 1−), with the latest example reported being unambiguously assigned as a Ln 2+ complex of the (C 6 H 6 ) 2− dianion.…”

A tetranuclear samarium(ii) inverse sandwich from direct reduction of toluene by a samarium(ii) siloxide

“…Reports of the formation of dinuclear arene-bridged Ln II/III complexes from the reduction of trivalent lanthanides complexes are more numerous. 5,[12][13][14][15][16][17] Although Ln II intermediates are likely to be involved in these reactions, the reduction of toluene or benzene by authenticated Ln II complexes has not been confirmed. Here, we report a unique example of an arene-bridged triple-decker Sm II complex that formed upon dissolution of the dinuclear .…”

“…Here, we report a unique example of an arene-bridged triple-decker Sm II complex that formed upon dissolution of the dinuclear . 12,13,20 The solid-state structure of 2 ( Fig. 1) shows a central toluene bridging two identical {KSmL 3 } units.…”