Homoleptic Rare-Earth Metal Complexes Containing Ln−C σ-Bonds

Zimmermann, Melanie; Anwander, Reiner

doi:10.1021/cr1001194

Cited by 277 publications

(227 citation statements)

References 450 publications

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“…The 1 H NMR spectrum of 1b (all NMR spectra reported were acquired in benzene-d 6 at room temperature unless otherwise specified) contained signals assigned on the basis of their relative integrated ratio, chemical shifts, and line widths. The last two properties are influenced by the nuclei's interaction with the paramagnetic center.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Homoleptic Divalent Dialkyl Lanthanide-Catalyzed Cross-Dehydrocoupling of Silanes and Amines

2016

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The rare-earth bis(alkyl) compound Sm{C-(SiHMe 2 ) 3 } 2 THF 2 (1b) is prepared by the reaction of samarium(II) iodide and 2 equiv of KC(SiHMe 2 ) 3 . This synthesis is similar to that of previously reported Yb{C-(SiHMe 2 ) 3 } 2 THF 2 (1a), and compounds 1a,b are isostructural. Reactions of 1b and 1 or 2 equiv of B(C 6 F 5 ) 3 afford SmC(SiHMe 2 ) 3 HB(C 6 F 5 ) 3 THF 2 (2b) or Sm{HB-(C 6 F 5 ) 3 } 2 THF 2 (3b), respectively, and 1,3-disilacyclobutane {Me 2 Si-C(SiHMe 2 ) 2 } 2 as a byproduct. Bands from 2300 to 2400 cm −1 assigned to ν BH in the IR spectra and highly paramagnetically shifted signals in the 11 B NMR spectra of 2b and 3b provided evidence for Sm-coordinated HB(C 6 F 5 ) 3 . Compounds 1a,b react with the bulky N-heterocyclic carbene (NHC) 1,3-di-tert-butylimidazol-2-ylidene (ImtBu) to displace both THF ligands and give three-coordinate monoadducts Ln{C-(SiHMe 2 ) 3 } 2 ImtBu (Ln = Yb (4a), Sm (4b)). Complexes 4a,b catalyze cross-dehydrocoupling of organosilanes with primary and secondary amines at room temperature to give silazanes and H 2 , whereas 1a,b are not effective catalysts under these conditions. Second-order plots of ln{[Et 2 NH]/[Ph 2 SiH 2 ]} vs time for 4a-catalyzed dehydrocoupling are linear and indicate first-order dependences on silane and amine concentrations. However, changes in the experimental rate law with increased silane concentration or decreased amine concentration reveal inhibition by silane. In addition, excess ImtBu or THF inhibit the reaction rate. These data, along with the structures of 4a,b, suggest that the bulky carbene favors low coordination numbers, which is important for accessing the catalytically active species.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Homoleptic Divalent Dialkyl Lanthanide-Catalyzed Cross-Dehydrocoupling of Silanes and Amines

2016

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“…These characteristics are also reflected in the organometallic chemistry of these elements: Eu(II) is so stable that it is just as common as Eu(III) in organometallic rare earth chemistry (Bombieri and Paolucci, 1998;Zimmermann and Anwander, 2010). Indeed, no homoleptic Eu(III) alkyl complexes have been reported yet (Zimmermann and Anwander, 2010), likely because the alkyl group is readily oxidized by Eu(III). Yb(II) is also common (Bombieri and Paolucci, 1998;Zimmermann and Anwander, 2010).…”

Section: Reduction Chemistry Of Organometallic Rare Earth Complexesmentioning

confidence: 99%

“…Indeed, no homoleptic Eu(III) alkyl complexes have been reported yet (Zimmermann and Anwander, 2010), likely because the alkyl group is readily oxidized by Eu(III). Yb(II) is also common (Bombieri and Paolucci, 1998;Zimmermann and Anwander, 2010). A major breakthrough in this field was the isolation of organosamarium(II) complexes.…”

Section: Reduction Chemistry Of Organometallic Rare Earth Complexesmentioning

confidence: 99%

“…Scandium(III) is the smallest among rare earths: its ionic radius of 0.74 Å is 0.12 Å smaller than that of lutetium(III) (Shannon, 1976). The large difference in ionic radius between scandium and other rare earths leads to special properties and reactivity of scandium complexes (Moeller et al, 1965;Zimmermann and Anwander, 2010). This is best illustrated by the product from the co-condensation of scandium metal and 1,3,5-t-Bu3C6H3 (Cloke et al, 1991).…”

Section: Scandium Fused-arene Complexes: Synthesis Characterizationmentioning

confidence: 99%

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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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“…[11][12][13] Although cyclopentadienyl ligands have dominated the chemistry of yttrium alkyl complexes for a long time, [3][4][5] recently, several groups have reported the synthesis of such compounds supported by noncyclopentadienyl ligands. [14][15][16] Our group has studied extensively the reactivity of group 3 metals and uranium alkyl complexes supported by diamide ligands towards heterocyclic aromatic compounds. [17][18] Benzyl complexes were found to ring open 1-methylimidazoles, [19][20][21][22][23] effect C-C coupling of pyridines, [24][25] and alkyl transfer to isoquinoline.…”

Section: Introductionmentioning

confidence: 99%

Yttrium-Alkyl Complexes Supported by a Ferrocene-Based Phosphinimine Ligand

Brosmer

Diaconescu

2015

Organometallics

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The synthesis and characterization of two yttrium alkyl complexes supported by a bisphosphinimine ferrocene ligand, NP by NMR spectroscopy, electrochemical measurements, and elemental analysis. Reactivity studies were also carried out, however, the lack of prolonged thermal stability at ambient temperature of these molecules led to decomposition before the clean formation of reaction products could be observed.1

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Homoleptic Rare-Earth Metal Complexes Containing Ln−C σ-Bonds

Cited by 277 publications

References 450 publications

Homoleptic Divalent Dialkyl Lanthanide-Catalyzed Cross-Dehydrocoupling of Silanes and Amines

Homoleptic Divalent Dialkyl Lanthanide-Catalyzed Cross-Dehydrocoupling of Silanes and Amines

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

Yttrium-Alkyl Complexes Supported by a Ferrocene-Based Phosphinimine Ligand

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