A family of neodymium complexes featuring a redox‐active ligand in three different oxidation states has been synthesized, including the iminoquinone (L0) derivative, (dippiq)2NdI3(
A family of neodymium complexes featuring a redox‐active ligand in three different oxidation states has been synthesized, including the iminoquinone (L0) derivative, (dippiq)2NdI3(
- PAR ID:
- 10039859
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 56
- Issue:
- 40
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 12142-12145
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 1‐iq ), the iminosemiquinone (L1−) compound, (dippisq)2NdI(THF) (1‐isq ), and the amidophenolate (L2−) [K(THF)2][(dippap)2Nd(THF)2] (1‐ap ) and [K(18‐crown‐6)][(dippap)2Nd(THF)2] (1‐ap crown ) species. Full spectroscopic and structural characterization of each derivative established the +3 neodymium oxidation state with redox chemistry occurring at the ligand rather than the neodymium center. Oxidation with elemental chalcogens showed the reversible nature of the ligand‐mediated reduction process, forming the iminosemiquinone metallocycles, [K(18‐crown‐6)][(dippisq)2Nd(S5)] (2‐isq crown ) and [K(18‐crown‐6)(THF)][(dippisq)2Nd(Se5)] (3‐isq crown ), which are characterized to contain a 6‐membered twist‐boat ring. -
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Abstract A family of cerium complexes featuring a redox‐active ligand in different oxidation states has been synthesized, including the the iminosemiquinone (isq)1−compound, Ce(dippisq)3(
1‐Ceisq ), and the amidophenolate (ap)2−species CeIII(dippap)3K3(2‐Ceap ), [CeIII(dippap)3K][K(18‐c‐6)]2(2‐Ceap 18c6 ), and [CeIII(dippap)3K][K(15‐c‐5)2]2(2‐Ceap 15c5 ). Treating2‐Ceap 15c5 with dioxogen furnishes the cerium(IV) derivative [CeIV(dippap)3][K(15‐c‐5)2]2(3‐Ceap 15c5 ), and an analogous synthesis can be used to generate [CeIV(dippap)3][K(crypt)]2(3‐Ceap crypt ). Similarly, addition of hexamethyldisiloxane produces an interesting bis(amidophenolate) species, [(Me3SiO)2CeIV(dippap)2][K(15‐c‐5)2]2(4‐CeOSiMe3 ). Full spectroscopic and structural characterization of each derivative was performed to establish the oxidation states of both the ligands and the cerium ions. -
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Abstract The chemical reduction of π‐conjugated bilayer nanographene
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Abstract The chemical reduction of π‐conjugated bilayer nanographene
1 (C138H120) with K and Rb in the presence of 18‐crown‐6 affords [K+(18‐crown‐6)(THF)2][{K+(18‐crown‐6)}2(THF)0.5][C138H1223−] (2 ) and [Rb+(18‐crown‐6)2][{Rb+(18‐crown‐6)}2(C138H1223−)] (3 ). Whereas K+cations are fully solvent‐separated from the trianionic core thus affording a “naked”1.3 −anion, Rb+cations are coordinated to the negatively charged layers of1.3 −. According to DFT calculations, the localization of the first two electrons in the helicene moiety leads to an unprecedented site‐specific hydrogenation process at the carbon atoms located on the edge of the helicene backbone. This uncommon reduction‐induced site‐specific hydrogenation provokes dramatic changes in the (electronic) structure of1 as the helicene backbone becomes more compressed and twisted upon chemical reduction, which results in a clear slippage of the bilayers. -
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1 , as well as [K(crypt)][Cp*2NdCl2],2 , and the previously reported [K(crypt)][Cp*2Nd(bipy)]. A mono‐Cp* Lu(III) complex, Cp*Lu(bipy)2,3 , was also found in an attempt to make Cp*2Lu(bipy) from LuCl3, 2 equiv. of KCp*, bipy, and K/KI. Surprisingly, the (bipy)1−ligands in neighboring molecules in the structure of3 are oriented in a parallel fashion with intermolecular C⋅⋅⋅C distances of 3.289(4) Å, which are shorter than the sum of van der Waals radii of two carbon atoms, 3.4 Å. Another product with one Cp* ligand per lanthanide was isolated from the reaction of [K(crypt)][Cp*2Eu(bipy)] with azobenzene, which afforded the dimeric Eu(II) complex, [K(crypt)]2[Cp*Eu(THF)(PhNNPh)]2,4 . Attempts to make4 from the reaction between Cp*2Eu(THF)2and a reduced azobenzene anion generated instead the mixed‐valent Eu(III)/Eu(II) complex, [K(crypt)][Cp*Eu(THF)(PhNNPh)]2,5 , which allows direct comparison with the bimetallic Eu(II) complex4 . Mono‐Cp* complexes of Yb(III) are obtained from reactions of the Yb(II) complex, [K(crypt)][Cp*2Yb(bipy)], with trimethylsilylazide, which afforded the tetra‐azido [K(crypt)]2[Cp*Yb(N3)4],6 , or the di‐azido complex [K(crypt)]2[Cp*Yb(N3)2(bipy)],7 a , depending on the reaction stoichiometry. A mono‐Cp* Yb(III) complex is also isolated from reaction of [K(crypt)][Cp*2Yb(bipy)] with elemental sulfur which forms the mixed polysulfido Yb(III) complex [K(crypt)]2[Cp*Yb(S4)(S5)],8 a . In contrast to these reactions that form mono‐Cp* products, reduction of Cp*2Yb(bipy) with 1 equiv. of KC8in the presence of 18‐crown‐6 resulted in the complete loss of Cp* ligands and the formation of [K(18‐c‐6)(THF)][Yb(bipy)4],9 . The (bipy)1−ligands of9 are arranged in a parallel orientation, as observed in the structure of3 , except in this case this interaction is intramolecular and involves pairs of ligands bound to the same Yb atom. Attempts to reduce further the Sm(II) (bipy)1−complex, Cp*2Sm(bipy) with 2 equiv. of KC8in the presence of excess 18‐crown‐6 led to the isolation of a Sm(III) salt of (bipy)2−with an inverse sandwich Cp* counter‐cation and a co‐crystallized K(18‐c‐6)Cp* unit, [K2(18‐c‐6)2Cp*]2[Cp*2Sm(bipy)]2 ⋅ [K(18‐c‐6)Cp*],10 .
