Direct hydrosilylation by a zirconacycle with β-hydrogen

Yan, KaKing; Pindwal, Aradhana; Ellern, Arkady; Sadow, Aaron D.

doi:10.1039/c4dt00658e

Cited by 10 publications

(6 citation statements)

References 40 publications

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“…Thus, the basicity of the bulkier silazido ligand N(SiMe 3 ) t Bu was invoked for reactions of Ln{N(SiMe 3 ) t Bu} 3 (Ln = Y, La) as a precursor to homogeneous hydroamination catalysts . Still, the SiH group in N(SiHMe 2 ) 2 provides a valuable spectroscopic handle for both NMR and IR analysis, stabilization of coordinatively and electronically unsaturated metal centers through labile secondary interactions, ,,, and a site for reactivity. − …”

Section: Introductionmentioning

confidence: 99%

β-SiH-Containing Tris(silazido) Rare-Earth Complexes as Homogeneous and Grafted Single-Site Catalyst Precursors for Hydroamination

et al. 2017

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A series of homoleptic rare-earth silazido compounds and their silica-grafted derivatives were prepared to compare spectroscopic and catalytic features under homogeneous and interfacial conditions. Trivalent tris-(silazido) compounds Ln{N(SiHMe 2 )tBu} 3 (Ln = Sc (1), Y (2), Lu (3)) are prepared in high yield by salt metathesis reactions. Solution-phase and solid-state characterization of 1− 3 by NMR and IR spectroscopy and X-ray diffraction reveals Ln↼H−Si interactions. These features are retained in solventcoordinated 2·Et 2 O, 2·THF, and 3·THF. The change in spectroscopic features characterizing the secondary interactions (ν SiH , 1 J SiH ) from the unactivated SiH in the silazane HN(SiHMe 2 )tBu follows the trend 3 > 2 > 1 ≈ 2·Et 2 O > 2·THF ≈ 3· THF. Ligand lability follows the same pattern, with Et 2 O readily dissociating from 2·Et 2 O while THF is displaced only during surface grafting reactions. 1 and 2·THF graft onto mesoporous silica nanoparticles (MSN) to give Ln{N(SiHMe 2 )tBu} n @MSN (Ln = Sc (1@MSN), Y (2@MSN)) along with THF and protonated silazido as HN(SiHMe 2 )tBu and H 2 NtBu. The surface species are characterized by multinuclear and multidimensional solid-state (SS) NMR spectroscopic techniques, as well as diffuse reflectance FTIR, elemental analysis, and reaction stoichiometry. A key 1 J SiH SSNMR measurement reveals that the grafted sites most closely resemble Ln·THF adducts, suggesting that siloxane coordination occurs in grafted compounds. These species catalyze the hydroamination/bicyclization of aminodialkenes, and both solution-phase and interfacial conditions provide the bicyclized product with equivalent cis:trans ratios. Similar diastereoselectivities mediated by catalytic sites under the two conditions suggest similar effective environments.

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Section: Introductionmentioning

confidence: 99%

β-SiH-Containing Tris(silazido) Rare-Earth Complexes as Homogeneous and Grafted Single-Site Catalyst Precursors for Hydroamination

et al. 2017

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“…The Zr–P distance of 2.71 Å is unexceptional and lies in the typical range observed for Cp 2 Zr–PMe 3 fragments. 47–49 The observation of a longer Zr–W distance in 3a compared to 1 (δ d Zr–W = 0.3 Å) suggests that metal–metal interactions play a negligible role in its bonding (see DFT section). Consistently, electron density corresponding to a bridging hydride was located in the Zr coordination plane, at an approximate distance of 2.0 Å from Zr and 1.7 Å from W, establishing a Zr–H–W angle of about 130° (average between the two independent molecules in the cell).…”

Section: Resultsmentioning

confidence: 99%

Tweaking the bridge in metallocene Zr(iv)/W(iv) bimetallic hydrides

et al. 2023

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“…Instead, Ln↼E–Si interactions typically are structural features of electron-poor complexes. , Recently, a few examples reveal that d 0 M↼H–Si or Ln↼H–Si interactions are reactive. The cationic or zwitterionic zirconium disilazidos [Cp 2 ZrN(SiHMe 2 ) 2 ] + and Cp 2 Zr{N(SiHMe 2 )(SiHMeCH 2 B(C 6 F 5 ) 3 )} react with acetone and formaldehyde to give hydrosilylation products [Cp 2 ZrN(SiMe 2 OR) 2 ] + (R = Me, CHMe 2 ) or Cp 2 Zr{N(SiMe 2 OR)(Si(OR)MeCH 2 B(C 6 F 5 ) 3 )}. , In addition, [Cp 2 ZrN(SiHMe 2 ) 2 ] + and 4-dimethylaminopyridine (dmap) react to give a zirconium hydride containing a dmap-coordinated silazido, [Cp 2 ZrH{N(SiHMe 2 )(SiMe 2 dmap)}] + , suggesting that the silicon is the most accessible electrophilic site in [Cp 2 ZrN(SiHMe 2 ) 2 ] + . In the initial communication of the present work, we reported that Y{N(SiHMe 2 )dipp} 3 (dipp = 2,6-diisopropylphenyl) and acetophenone react via hydrosilylation .…”

Section: Introductionmentioning

confidence: 99%

Ancillary Steric Effects on the Activation of SiH Bonds in Arylsilazido Rare-Earth Compounds

et al. 2021

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Three new hydridosilazido ligands, -N(SiHMe2)Aryl (Aryl = Ph, 2,6-C6Me2H3 (dmp), 2,6-C6iPr2H3 (dipp)) and their rare earth complexes Ln{N(SiHMe2)Aryl}3(THF)n (Ln = Sc, Y, Lu; Aryl = Ph, n = 2; Aryl = dmp, n = 1; Aryl = dipp, n = 0) were synthesized to study the relationships between ligand steric properties, secondary Ln↼H-Si bonding, and the reactivity of amide and SiH groups. In these compounds, the steric encumbrance of the aryl group was systematically increased from phenyl to 2,6-dimethylphenyl to 2,6-diisopropylphenyl. NMR, IR and X-ray diffraction studies of the complexes characterize the number of secondary interactions and additional THF ligands coordinated to the rare earth centers. The complexes with the smallest phenylsilazido ligands, Ln{N(SiHMe2)Ph}3(THF)2, contain features associated with three non-bridging 2c-2e Si-H. Characterization of intermediate-sized Ln{N(SiHMe2)dmp}3THF reveals three and two Ln↼H-Si interactions for yttrium and lutetium analogues, respectively, with both metals having one coordinated THF per complex. Ln{N(SiHMe2)dipp}3 is formed solvent-free, and all three ligands adopt Ln↼H-Si bonding modes. The reaction between Ln{N(SiHMe2)dipp}3 and ketones provides the hydrosilylated product via addition of C=O and Si-H bonds, which occurs rapidly even at low temperature. This reaction is proposed to occur through an associative mechanism on the basis of negative activation entropy measured for substitution of pyridine in Ln{N(SiHMe2)dipp}3•NC5H5.

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Direct hydrosilylation by a zirconacycle with β-hydrogen

Cited by 10 publications

References 40 publications

β-SiH-Containing Tris(silazido) Rare-Earth Complexes as Homogeneous and Grafted Single-Site Catalyst Precursors for Hydroamination

β-SiH-Containing Tris(silazido) Rare-Earth Complexes as Homogeneous and Grafted Single-Site Catalyst Precursors for Hydroamination

Tweaking the bridge in metallocene Zr(iv)/W(iv) bimetallic hydrides

Ancillary Steric Effects on the Activation of SiH Bonds in Arylsilazido Rare-Earth Compounds

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