Structural Characterization of a Tris‐Agostic LanthanoidHSi Interaction

Rees, William S.; Just, Oliver; Schumann, Herbert; Weimann, Roman

doi:10.1002/anie.199604191

Cited by 59 publications

(46 citation statements)

References 29 publications

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“…FTIR spectroscopy offers another efficient tool to study Ln···H-Si interactions. [9][10][11][12][13] For complexes 2, the peculiar Si-H stretching vibrations are characterized by pronounced low-energy shoulders in the area 1900 to 2000 cm -1 typical of weak agostic interactions (Table 1). [9][10][11][12][13] Generally, strong M···H-Si agostic interactions fall in the range 1700 to 1900 cm -1 .…”

Section: Introductionmentioning

confidence: 99%

Donor and ate‐Coordination in Rare‐Earth Metal Bis(dimethylsilyl)amide Complexes

et al. 2008

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Section: Introductionmentioning

confidence: 99%

Donor and ate‐Coordination in Rare‐Earth Metal Bis(dimethylsilyl)amide Complexes

et al. 2008

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“…35 Particular attention is devoted to investigate the correlation between the main MOCVD process parameters that control interface reactivity, Er 2 O 3 nucleation and growth, and, consequently, film characteristics. Furthermore, the structural, morphological, electrical, and optical properties of Er 2 O 3 films are also reported.…”

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confidence: 99%

“…ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14 35. Downloaded on 2015-03-17 to IP…”

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confidence: 99%

Structural and Optical Properties of Nanocrystalline Er[sub 2]O[sub 3] Thin Films Deposited by a Versatile Low-Pressure MOCVD Approach

Losurdo

Giangregorio

Capezzuto

et al. 2008

J. Electrochem. Soc.

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Nanocrystalline Er 2 O 3 thin films have been grown on Si͑100͒ by low-pressure metallorganic chemical vapor deposition in the temperature range of 450-700°C using the tris͑isopropylcyclopentadienyl͒erbium precursor and O 2 . The growth kinetics has been investigated in real time using laser reflectance interferometry as a function of growth parameters, and three different steps have been highlighted: ͑i͒ the incubation, ͑ii͒ the nucleation, and ͑iii͒ the growth stages. It is demonstrated that functionalization of the Si substrate surface is important for shortening the incubation time and, consequently, reducing subcutaneous oxidation of the Si substrate and for preventing nonhomogeneous nucleation that yields rough films. The growth kinetics has been correlated with film properties. X-ray diffraction patterns show strongly ͑111͒ oriented Er 2 O 3 thin films even at temperature as low as 400°C; however, a deposition temperature of 600°C is optimal for obtaining films with highest refractive index and lowest surface roughness ͑root-mean-square = 0.4 nm͒. Transmission electron microscopy shows very sharp interfaces and compact films. Spectroscopic ellipsometry analysis of the optical properties shows a very high refractive index comparable to that of Er 2 O 3 single crystal and a very high transparency in the visible-ultraviolet energy photon range.Recently, the rare-earth metal oxides ͑REOs͒, either in the form of nanocrystals 1 or thin films, 2-6 have been the subject of intense research efforts because they exhibit interesting chemical and physical properties, such as high transparency from the ultraviolet to the infrared, high refractive index, good dielectric and insulating properties, and a relatively high static dielectric constant. 3,7 Therefore, thin films and coatings of REOs have great potentiality for applications in various fields of science and technology, including photonics, optics, semiconductor devices, and telecommunications. 8 Recently, REO films have also been studied as an alternative gate dielectric to replace SiO 2 in complementary-metal-oxidesemiconductor ͑CMOS͒ devices of the forthcoming generations. 3,9,10 Among these materials, erbium oxide ͑Er 2 O 3 ͒ has been believed to be a promising high-k oxide on silicon substrates. In fact, Er 2 O 3 has a lattice constant of ϳ10.54 Å, which is nearly two times the lattice constant of silicon, and, due to its small ionic radius, Ono and Katsumata 10 have reported that Er 2 O 3 reacts poorly with silicon during annealing, even at 900°C, compared to the other REOs, such as La 2 O 3 and Gd 2 O 3 .Physical approaches, including molecular beam epitaxy, 9,11 sputtering, 8 electron beam evaporation, 12-15 and atomic layer deposition ͑ALD͒, 16,17 have mainly been used to grow Er 2 O 3 thin films. Few reports exist on the metallorganic chemical vapor deposition ͑MOCVD͒ of Er 2 O 3 , which is particularly well suited to large-scale manufacturing procedures for microelectronics. [18][19][20] Thus far, precursors such as alkoxide and ␤-diketonates, which are ...

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“…The selection of the -N(t-Bu)(SiHMe 2 ) ligand was based on the documented propensity of this substituent to engage in agostic bonding of the Si-H moiety to group 3 metals. 6 After complex formation was completed, THF was removed in vacuo and replaced by C 6 D 6 prior to the addition of the aminoalkenes (Scheme 1).…”

Section: Catalyst Generationmentioning

confidence: 99%

Enantioselective hydroamination/cyclization of aminoalkenes by (bis)-C2 symmetric and (mono)-C2 symmetric anionic tetraamide complexes of La(III)

Huynh

Anderson

Livinghouse

2015

Tetrahedron Letters

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a b s t r a c tEnantioselective hydroamination/cyclizations of several monosubstituted and disubstituted aminoalkenes have been achieved, catalyzed by tetracoordinate anionic La(III) complexes.Ó 2015 Published by Elsevier Ltd.The intramolecular hydroamination of alkenes constitutes a powerful and atom-economical method for the synthesis of nitrogen-containing heterocycles. 1,2 Both neutral and anionic complexes of Y(III) have shown utility in the asymmetric variation of this process. 3a,b We recently disclosed that neutral chelating diamide complexes of several group 3 metals prepared from simple N-(diaryl)methyl substituted diamide motifs derived from (R)-1,1 0 -binapthyl-2-2 0 -diamine are effective catalysts for enantioselective hydroamination/cyclization. 4 We subsequently demonstrated that (R)-N,N 0 -dibenzosuberyl-1,1 0 -binaphthyl-2,2 0 -diamine (1) is a vastly superior proligand for this process and showed that the chelating diamide complexes derived from La(III), the largest lanthanide metal, provided higher enantioselectivities than the more sterically congested Y(III) congeners. 5 In this communication, we describe the reactivity and enantioselectivity for intramolecular hydroamination catalyzed by a new family of Y(III)and La(III) ate-complexes originating from enantiopure 1 and achiral amide ligands. Catalyst generationThe catalytic complexes, 8a,b, 9a,b, and 10a-d utilized in this study were prepared by the following procedure. Sequential treatment of YCl 3 (THF) 3.5 or LaCl 3 (THF) 1.5 (1 equiv each) with Me 3 SiCH 2 Li (4 equiv) in THF generated solutions of the corresponding anionic homoleptic alkyl (Me 3 SiCH 2 ) 4 M À Li + complexes (4a: M = Y, 4b: M = La). Immediate addition of 1 (1 equiv, 20 min, 23°C) delivered the preformed solutions of 4a,b. Addition of supporting ligands 6, 7, or 1 (1 equiv each) subsequently afforded solutions of the anionic complexes 8a,b, 9a,b, and 10a,b. The anionic complex 10c (M 1 = La, M 2 = Na) was generated by the sequential treatment of 1 (2 equiv) with La[N(t-Bu)(TMS)] 3 5 (1 equiv) followed by NaN(TMS) 2 (1 equiv), whereas the neutral complex 10d was prepared by the treatment of 1 (2 equiv) with La[N(t-Bu)(TMS)] 3 (1 equiv). The tetra(amide) complexes 5a and 5b were directly prepared by amine elimination involving the sequential exposure of YCl 3 (THF) 3.5 or LaCl 3 (THF) 1.5 to LiN(t-Bu)(SiHMe 2 ) (4 equiv) followed by 1 (1 equiv). The selection of the -N(t-Bu)(SiHMe 2 ) ligand was based on the documented propensity of this substituent to engage in agostic bonding of the Si-H moiety to group 3 metals. 6 After complex formation was completed, THF was removed in vacuo and replaced by C 6 D 6 prior to the addition of the aminoalkenes (Scheme 1). Enantioselective hydroamination studiesWe initiated this investigation by examining the enantioselective hydroamination/cyclization of aminoalkene 11a catalyzed by anionic ate-complexes 4a and 4b. Cyclization of 11a in the http://dx.

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Structural Characterization of a Tris‐Agostic LanthanoidHSi Interaction

Cited by 59 publications

References 29 publications

Donor and ate‐Coordination in Rare‐Earth Metal Bis(dimethylsilyl)amide Complexes

Donor and ate‐Coordination in Rare‐Earth Metal Bis(dimethylsilyl)amide Complexes

Structural and Optical Properties of Nanocrystalline Er[sub 2]O[sub 3] Thin Films Deposited by a Versatile Low-Pressure MOCVD Approach

Enantioselective hydroamination/cyclization of aminoalkenes by (bis)-C2 symmetric and (mono)-C2 symmetric anionic tetraamide complexes of La(III)

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