Expanding Rare-Earth Oxidation State Chemistry to Molecular Complexes of Holmium(II) and Erbium(II)

MacDonald, Matthew R.; Bates, Jefferson E.; Fieser, Megan E.; Ziller, Joseph W.; Furche, Filipp; Evans, William J.

doi:10.1021/ja303357w

Cited by 201 publications

(294 citation statements)

References 49 publications

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“…2 The expected structural changes between Y 3+ and Y 2+ complexes are well reproduced by the calculations. In addition, MPA analysis of the Y 2+ HOMOs was successful in correlating the percent metal and percent s character in the reduced molecules with their experimentally observed EPR hyperfine coupling constants, Table 6.…”

Section: ■ Discussionmentioning

confidence: 52%

Ligand Effects in the Synthesis of Ln²⁺ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion

et al. 2015

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The tris(cyclopentadienyl) yttrium complexes Cp 3 Y-(THF), Cp Me 3 Y(THF), Cp″ 3 Y, Cp″ 2 YCp, and Cp″ 2 YCp Me [Cp = C 5 H 5 , Cp Me = C 5 H 4 Me, Cp″ = C 5 H 3 (SiMe 3 ) 2 ] have been treated with potassium graphite in the presence of 2.2.2-cryptand to search for more stable examples of complexes featuring the recently discovered Y 2+ ion first isolated in [K(18-crown-6)][Cp′ 3 Y] and [K(2.2.2-cryptand)][Cp′ 3 Y], 1-Y (Cp′ = C 5 H 4 SiMe 3 ). Reduction of the tris(cyclopentadienyl) complexes generates dark solutions like that of 1-Y, and the EPR spectra contain doublets with g values between 1.990 and 1.991 and hyperfine coupling constants of 34−47 gauss that are consistent with the presence of Y 2+ . [K(2.2.2-cryptand)][Cp″ 2 YCp], 2-Y, was characterizable by X-ray crystallography. Reduction of the Cp″ 3 Gd, Cp″ 2 GdCp, and Cp″ 2 GdCp Me complexes containing the larger metal gadolinium were also examined. In each case, dark solutions and EPR spectra like that of [K(2.2.2-cryptand)][Cp′ 3 Gd], 1-Gd, were obtained, and [K(2.2.2-cryptand)][Cp″ 2GdCp], 2-Gd, was crystallographically characterizable. None of the new yttrium and gadolinium complexes displayed greater stability than 1-Y and 1-Gd. Exploration of this reduction chemistry with indenyl ligands did not give evidence for +2 complexes. The only definitive information obtained from reductions of the Cp In 3 Ln (Cp In = C 9 H 7 , Ln = Y, Ho, Dy) complexes was the X-ray crystal structure of {K(2.2.2-cryptand)} 2 {[(C 9 H 7 ) 2 Dy(μ−η 5 :η 1 -C 9 H 6 )] 2 }, a complex containing the first example of the indenyl dianion, (C 9 H 6 ) 2− , derived from C−H bond activation of the (C 9 H 7 ) 1− monoanion. Density functional theory analysis of these results provides an explanation for the observed hyperfine coupling constants in the yttrium complexes and for the C−H bond activation observed for the indenyl complex. ■ INTRODUCTIONRecent studies of the reduction chemistry of yttrium and the f elements have shown that the +2 ions are available for yttrium, 1 all the lanthanides 2−4 (except promethium, which was not studied due to its radioactivity), uranium, 5 and thorium. 6 These new oxidation states have been obtained by reduction of the tris(cyclopentadienyl) complexes, Cp′ 3 M and Cp″ 3 M [Cp′ = C 5 H 4 SiMe 3 , M = Y, lanthanide, U; Cp″ = C 5 H 3 (SiMe 3 ) 2 , M = La, Ce, Th] to form (Cp′ 3 M) 1− and (Cp″ 3 M) 1− complexes, Schemes 1 and 2.Structural, spectroscopic, and density functional theory analyses suggest that these new ions could be accessed for the first time because the (Cp′ 3 ) 3− and (Cp″ 3 ) 3− ligand sets allow the d z 2 orbital to be populated such that the new ions have 4f n 5d 1 electron configurations for the lanthanides, 5f 3 6d 1 for uranium, 6d 2 for thorium, and 4d 1 for yttrium. This is consistent with numerous theoretical analyses of the f elements in trigonal tris(cyclopentadienyl) coordination environments. 8−13 Whereas reduction of a 4f n Ln 3+ ion to a 4f n+1 Ln 2+ product would be difficult due to the highly negative calculated generic r...

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Section: ■ Discussionmentioning

confidence: 52%

Ligand Effects in the Synthesis of Ln²⁺ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion

et al. 2015

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“…106 However, chemists never stopped pushing synthetic limits and, recently, low valent lanthanide chemistry has emerged as a fast developing field. [107][108][109] Recent advancements feature the synthesis and characterization of divalent lanthanide complexes for the complete lanthanide series, [110][111][112][113][114][115][116] reduced dinitrogen complexes, [117][118][119][120][121] reduced arene complexes, 26-29, 57, 122-126 and bimetallic reductive cleavage of aromatic C-H bonds. 40,44 Our group focused on the reduction chemistry of rare-earth metal complexes with non-innocent  ligands, followed by a small molecule activation study.…”

Section: Reduction Chemistry With  Ligands and Small Molecule Actmentioning

confidence: 99%

Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Huang

Diaconescu

2016

Inorg. Chem.

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Our group has focused on the organometallic chemistry of rare-earth metals and actinides for a decade. By installing ferrocene diamide ligands at electropositive metal centers, we have been able to disclose unprecedented reactivity toward aromatic N-heterocycles, arenes, and other small molecules such as P 4 . Systematic studies employing X-ray crystallography, spectroscopy, cyclic voltammetry, and DFT calculations revealed that the ferrocene backbone could stabilize the electron-deficient metal through a donor-acceptor type interaction. Most noteworthy is that this interaction can be readily turned on or off by the addition or removal of a Lewis base. In addition to its flexible coordination, the redox active nature of the ferrocene backbone enabled us to explore redox-switchable transformations. The introduction of ferrocene-based ligands into organolanthanide chemistry not only helped to study intriguing fundamental problems but also led to fruitful chemistry including small molecule activation and controlled co-polymerization reactions.3

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“…The authors proposed that it contains a lanthanum(II) ion. Recently, Evans extended this chemistry to almost all the lanthanides (Chart 10) (MacDonald et al, 2011;MacDonald et al, 2012;MacDonald et al, 2013a). The charge balance requires the lanthanide ion to be in +2 oxidation state.…”

Section: Reduction Chemistry Of Organometallic Rare Earth Complexesmentioning

confidence: 99%

Rare Earth Arene-Bridged Complexes Obtained by Reduction of Organometallic Precursors

Huang

Diaconescu

2014

Including Actinides

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Rare earth chemistry has witnessed remarkable advances in recent years. In particular, ancillary ligands other than cyclopentadienyl derivatives have been introduced to the organometallic chemistry and their complexes exhibit distinct reactivity and properties compared to the metallocene or half-sandwiched analogues. The present chapter reviews arene-bridged rare earth complexes with an emphasis on those compounds obtained by reduction reactions. A particular emphasis is placed on rare earth complexes supported by 1,1′-ferrocenediyl diamides since they show the most diverse chemistry with arenes: fused arenes, such as naphthalene and anthracene, formed inverse-sandwiched complexes, in which the arene is dianionic; weakly conjugated arenes, such as biphenyl, p-terphenyl, and 1,3,5-triphenylbenzene, were unexpectedly reduced by four electrons and led to 6-carbon, 10- electron aromatic systems; on the contrary, (E)-stilbene, which has a carbon-carbon double bond between the two phenyl rings, could only be reduced by two electrons, which were located on the carbon-carbon double bond instead of the phenyl rings.

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Expanding Rare-Earth Oxidation State Chemistry to Molecular Complexes of Holmium(II) and Erbium(II)

Cited by 201 publications

References 49 publications

Ligand Effects in the Synthesis of Ln²⁺ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion

Ligand Effects in the Synthesis of Ln²⁺ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion

Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Rare Earth Arene-Bridged Complexes Obtained by Reduction of Organometallic Precursors

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Expanding Rare-Earth Oxidation State Chemistry to Molecular Complexes of Holmium(II) and Erbium(II)

Cited by 201 publications

References 49 publications

Ligand Effects in the Synthesis of Ln2+ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion

Ligand Effects in the Synthesis of Ln2+ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion

Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Rare Earth Arene-Bridged Complexes Obtained by Reduction of Organometallic Precursors

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Ligand Effects in the Synthesis of Ln²⁺ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion

Ligand Effects in the Synthesis of Ln²⁺ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C–H Bond Activation of an Indenyl Anion