Steric Effects in Lanthanide Sandwich Complexes Containing Bulky Cyclooctatetraenyl Ligands

Edelmann, Anja; Lorenz, Volker; Hrib, Cristian G.; Hilfert, Liane; Blaurock, Steffen; Edelmann, Frank T.

doi:10.1021/om3010993

Cited by 41 publications

(46 citation statements)

References 56 publications

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“…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) .…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Five new lanthanide(III) sandwich and half‐sandwich complexes with bulky cyclooctatetraenyl ligands have been prepared and fully characterized, including single‐crystal X‐ray structure determination. The treatment of anhydrous lanthanide(III) chlorides, LnCl3 (Ln = Pr, Tb, Yb), with 2 equivalents of Li2COT′′ [COT′′ = 1,4‐bis(trimethylsilyl)cyclooctatetraene dianion] followed by crystallization in the presence of a coordinating solvent afforded the anionic sandwich complexes [Li(THF)4][Pr(COT′′)2] (1), [Li(DME)3][Tb(COT′′)2] (2; DME = 1,2‐dimethoxyethane), and [Li(TMEDA)2][Yb(COT′′)2] (3; TMEDA = N,N,N′,N′‐tetramethylethylenediamine). Attempted oxidation of 2 with silver iodide did not afford the neutral terbium(IV) sandwich complex [Tb(COT′′)2]. Instead, the tri(µ‐iodido)‐bridged dinuclear half‐sandwich complex [Li(DME)2][Tb2(µ‐I)3(COT′′)2] (4) was isolated in 72 % yield. In this complex, the Li(DME)2 fragment is attached to one of the µ‐iodido ligands. A closely related binuclear lutetium complex, [Li(DME)3][Lu2(µ‐Cl)3(COTbig)2]·DME (5), was obtained by using the “superbulky“ COTbig ligand [COTbig = 1,4‐bis(triphenylsilyl)cyclooctatetraenyl dianion]. In addition to the spectroscopic and structural characterization, the magnetic properties of the paramagnetic terbium(III) derivative 2 have been investigated and further complemented by ab initio computational methods. These results have been used to discuss the structural requirements for potential terbium(III) single‐ion magnets.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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“…Uranocene is unreactive to lithiation, 9 and all reported trivalent uranocene-type complexes have been prepared via reduction of [U IV (COT-R) 2 ] (R = CH 3 , 10 13 Single crystals of 3 were grown in a concentrated solution of a 50:50 mixture of DME/hexanes. Complex 1 crystallizes in the triclinic P1̅ space group where the U III ion is bound to two COT″ ligands in a η 8 -fashion to form a distorted sandwich complex.…”

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Slow Magnetic Relaxation in Uranium(III) and Neodymium(III) Cyclooctatetraenyl Complexes

et al. 2015

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The synthesis, structure, and magnetic properties of a uranium(III) sandwich complex, [Li(DME) 3 ][U III (COT″) 2 ] (COT″ = bis(trimethylsilyl)cyclooctatetraenyl dianion), and its coordinatively analogous tetravalent equivalent, [U IV (COT″) 2 ], were investigated. Additionally, a full structural and magnetic comparison to the isostructural and isoelectronic lanthanide complex, [Li(DME) 3 ][Nd III (COT″) 2 ], is provided. DFT calculations reveal that the U III complex leads to weaker ligand-to-metal donation as compared with the tetravalent equivalent complex. Alternating current magnetic susceptibility results reveal slow magnetic relaxation in both U III and Nd III complexes. The enhanced magnetic performance of the U III congener further encourages the use of actinides in the design of single-molecule magnets.T remendous effort has been put forth toward improving lanthanide single-molecule magnets (SMMs) for their use in magnetic materials. 1 Many of the best candidates thus far have been single-ion lanthanide complexes, which display remarkable magnetic properties due to unquenched orbital angular momentum. 2 However, the operating temperature of even the best lanthanide SMMs is well below what is required for practical applications. One of the main challenges toward higher temperature lanthanide SMMs is synthesizing magnetic complexes with strong superexchange-type metal−metal interactions, where metals are strongly coupled through diamagnetic bridging ligands. This requires strong metal−ligand covalency, which is challenging due to the poor radial extension of 4f orbitals.Uranium complexes have tremendous potential as SMMs, as they possess the key physical properties of large intrinsic total ground state spin (S) and more importantly uniaxial magnetic anisotropy (D) required for magnet-like behavior of slow relaxation of the magnetization. 3 Akin to lanthanide ions, the heavy-element nature of uranium can additionally result in significant spin−orbit coupling constants. 4 However, unlike lanthanides, actinides have enhanced 5f radial extension, which leads to substantial metal−ligand covalency, allowing for strong exchange coupling (J) between metals in multimetallic complexes.Despite the many obvious advantages, only a handful of actinide SMMs have been reported, none of which have shown enhance magnetic properties over the best performing lanthanide SMMs. 5 It is well established that even subtle variations in the ligand field can drastically change the magnetic properties of lanthanide SMMs. 6 Therefore, in order to isolate new uranium SMMs with large anisotropic barriers, it is important to explore how new ligand fields effect the magnetic properties of actinides.With this in mind we have turned our attention toward uranocene-type sandwich complexes. The influence of a sandwich-type ligand field is unknown on the SMM properties of uranium. Moreover, strong ligand donation has been well established in uranocene [U VI (COT) 2 ], which is a desirable property in a magnetic building block. 7 However, magnet...

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“…In this compound the bulky COT leads to coordination of only one THF per Ln in comparison to the long-known parent chloro-bridged dimers [(COT)Ln(-Cl)(THF) 2 ] 2 [87].…”

Section: Lanthanide Cyclooctatetraenyl Complexesmentioning

confidence: 98%

“…It was found that the steric effect of either COT or COT TBS on the molecular structures of the anionic sandwich complexes with coplanar ring ligands is rather small. In (COT )Yb(DippForm)(THF), the combination of COT with a sterically demanding formamidinate ligand in the coordination sphere of Yb 3+ still leaves room for THF coordination [87].…”

Section: Lanthanide Cyclooctatetraenyl Complexesmentioning

confidence: 99%

“…Quite surprisingly, an attempt to prepare the holmium analog of the known linear triple-decker sandwich complex (COT )Nd(-8 : 8 -COT )Nd(COT ) led to formation of the isomerized triple-decker (COT )Ho[-8 : 8 -C 8 H 6 (SiMe 3 ) 2 -1,5]Ho(COT ), as a result of steric pressure-induced silyl group migration (Scheme 112)[87].Single-ion magnet (SIM) and single-molecule magnet (SMM) behavior have also be found for the new homoleptic [Li(THF) 4 ][Dy(COT ) 2 ] and Ln 2 (COT ) 3 (Ln = Gd, Dy) complexes which have been synthesized according to Scheme 113. The tripledecker sandwich complexes were prepared using the previously reported CoCl 2 oxidation method (cf.…”

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confidence: 99%

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Steric Effects in Lanthanide Sandwich Complexes Containing Bulky Cyclooctatetraenyl Ligands

Cited by 41 publications

References 56 publications

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

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

Slow Magnetic Relaxation in Uranium(III) and Neodymium(III) Cyclooctatetraenyl Complexes

Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2013

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