Reactions of zirconium amide amidinates with dioxygen. Observation of an unusual peroxo intermediate in the formation of oxo compounds

Lamb, Adam C.; Lü, Zheng; Chen, Xue-Tai

doi:10.1039/c4cc04032e

Cited by 9 publications

(6 citation statements)

References 52 publications

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“…The presence of one tridentate and four bidentate ligands in the inner sphere creates a rare 11-coordinate environment around the thorium(IV) centers that are best described as augmented sphenocorona. A similar [M 3 (O 2 ) 3 ] core has been observed in several zirconium(IV) fluorides as well as in {Zr[MeC(N i Pr) 2 ] 2 (O 2 )} 3 . , In the latter compound, it was established that the reduction of O 2 to O 2 2– is ligand-based and appropriate ligand decomposition products are observed. However, this cluster is unstable in solution and ultimately decomposes to dimeric and polymeric oxo species via degradation of the peroxide anions.…”

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confidence: 65%

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Understanding the Scarcity of Thorium Peroxide Clusters

et al. 2017

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The reaction of Th(NO)·5HO with 3 equiv of 2,2',6',2″-terpyridine (terpy) in a mixture of acetonitrile and methanol results in formation of the trinuclear thorium peroxide cluster [Th(O)(terpy)(NO)]. This cluster is assembled via bridging by μ-η:η peroxide anions between thorium centers. It decomposes upon removal from the mother liquor to yield Th(terpy)(NO) and Th(terpy)(NO)(EtOH). The peroxide formation appears to be radiolytic in origin and is, most likely, generated from radiolysis of water by short-lived daughters generated from Th decay. This cluster does not form when freshly recrystallized Th(NO)·5HO is used as the starting material and requires an aged source of thorium. Analysis of the bonding in these clusters shows that, unlike uranium(VI) peroxide interactions, thorium(IV) complexation by peroxide is quite weak and largely ionic. This explains its much lower stability, which is more comparable to that observed in similar zirconium(IV) peroxide clusters.

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“…The reaction of Th(NO 3 ) 7,8 In the latter compound, it was established that the reduction of O 2 to O 2 2− is ligand-based and appropriate ligand decomposition products are observed. However, this cluster is unstable in solution and ultimately decomposes to dimeric and polymeric oxo species via degradation of the peroxide anions.…”

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Understanding the Scarcity of Thorium Peroxide Clusters

et al. 2017

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“…Very little is known about the reactions of d 0 transition-metal complexes with O 2 , which is in part due to their air sensitivity, requiring work under inert gases and vacuum . Our group has studied the reaction between the alkyl amide imide complex Ta(CH 2 Bu t ) 2 (NSiMe 3 )[N(SiMe 3 ) 2 ] and O 2.…”

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Syntheses and Characterization of Tantalum Alkyl Imides and Amide Imides. DFT Studies of Unusual α-SiMe₃ Abstraction by an Amide Ligand

et al. 2015

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Reaction of TaCl2(NSiMe3)[N(SiMe3)2] (1) with alkylating reagents form the alkyl amide imide complexes TaR2(NSiMe3)[N(SiMe3)2] (R = Me (2), CH2Ph (3)) and mixed amide imide compounds Ta(NR′2)2(NSiMe3)[N(SiMe3)2] (R′ = Me (4), Et (5)). The reaction of 2 and 0.5 equiv of O2 leads to preferential oxygen insertion into one Ta–Me bond, yielding the alkoxy-bridged alkyl dimer Ta2(μ-OMe)2Me2(NSiMe3)2[N(SiMe3)2]2 (6) as cis and trans isomers. Crystallization of the cis -6 and trans -6 mixture gave only crystals of trans -6. When the crystals of trans -6 were dissolved in benzene-d 6, conversion of trans -6 to cis -6 occurred until the trans -6 ⇌ cis -6 equilibrium was reached with K eq = 0.79(0.02) at 25.0(0.1) °C. Kinetic studies of the exchange gave the rate constants k = 0.018(0.002) min–1 for the trans -6 → cis -6 conversion and k′ = 0.022(0.002) min–1 for the reverse cis -6 → trans -6 conversion at 25.0(0.1) °C. Complex 6 reacts with additional O2, forming the dialkoxy dimer Ta2(μ-OMe)2(OMe)2(NSiMe3)2[N(SiMe3)2]2 (7) as cis and trans isomers. Solid-state structures of 3 and trans -6 have been determined by X-ray diffraction analyses. The mixed amide imide compounds Ta(NR′2)2(NSiMe3)[N(SiMe3)2] (R′ = Me (4), Et (5)) have also been prepared by salt metathesis reactions employing TaCl3[N(SiMe3)2]2 (8). The pathway from 8 to 4 and 5 eliminates Me3Si–NR′2 (R′ = Me, Et), converting the amide N(SiMe3)2 ligand to the imide NSiMe3 ligand. Such intramolecular imidation is rare. The mechanism of this process has been computationally probed, and α-elimination involving the mixed amide species TaCl2(NMe2)[N(SiMe3)2]2 (9) is discussed. Diffusion-ordered spectroscopy (DOSY) studies of 1–6 and 8 show that only the alkoxy-bridged cis- 6 and trans -6 are dimers in benzene-d 6 solution at 25 °C.

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“…Group 4 complexes with multiple amidinate ligands have been previously reported including a small number of tris , and tetrakis amidinate complexes, although these are limited to small N -alkyl groups. , Bis(amidinate) complexes are more common, including those whereby the ligating groups are tethered by a bridge, , although the choice of N , N ′-substituents is relatively limited (SiMe 3 , − i Pr, − Cy, − C(Me)Ph, C 6 F 5 , Dipp, and Xyl) . Depending on the nature of the amidinate ligand, the N , N ′ groups can also be C–H-activated; Hessen and co-workers reported that Zr{N(2,6- i Pr-C 6 H 3 ) 2 CH}Me 2 can be thermolyzed at 50 °C, resulting in double C–H bond activation of the isopropyl methyl groups and cyclometallation to afford Zr{N(2- i Pr-6-CMe 2 -C 6 H 3 ) 2 CH} 2 .…”

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Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

et al. 2022

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The synthesis and characterization of new zirconium permethylpentalene (form)amidinate complexes are described: Pn*Zr{N(Dipp)2CH}Cl (1), Pn* = η8-C8Me6 and Dipp = 2,6- i Pr-C6H3; [Pn*Zr{N(p-tol)2CH}Cl]2 (2), p-tol = 4-Me-C6H4; [Pn*Zr{N( i Pr)2CMe}Cl]2 (3); Pn*Zr{N( i Pr)2CPh}Cl (4); Pn*Zr{N(4-Me-C6H4)2CH}2 (5); [Pn*Zr{N( i Pr)2CCH2}]2 (6); and Pn*Zr{N( i Pr)2CPh}(O-2,6,-Me-C6H3) (7). The monohalide derivatives 1–4 demonstrate considerable structural diversity as the nature of the (form)amidinate-supporting ligand is changed. While complexes with acidic backbone protons proved susceptible to deprotonation using mild bases, those without underwent straightforward salt metathesis reactions with alkali metal salts, leading to complexes [Pn*Zr{N( i Pr)2CCH2}]2 (6) and Pn*Zr{N( i Pr)2CPh}(O-2,6-Me-C6H3) (7). Preliminary slurry-phase ethylene polymerization studies are also reported using complexes 2, 4, 5, and 7 to gain a direct comparison to the highly active, yet electronically saturated, Pn*Zr(CpR)Cl catalyst family.

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Reactions of zirconium amide amidinates with dioxygen. Observation of an unusual peroxo intermediate in the formation of oxo compounds

Cited by 9 publications

References 52 publications

Understanding the Scarcity of Thorium Peroxide Clusters

Understanding the Scarcity of Thorium Peroxide Clusters

Syntheses and Characterization of Tantalum Alkyl Imides and Amide Imides. DFT Studies of Unusual α-SiMe₃ Abstraction by an Amide Ligand

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

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Reactions of zirconium amide amidinates with dioxygen. Observation of an unusual peroxo intermediate in the formation of oxo compounds

Cited by 9 publications

References 52 publications

Understanding the Scarcity of Thorium Peroxide Clusters

Understanding the Scarcity of Thorium Peroxide Clusters

Syntheses and Characterization of Tantalum Alkyl Imides and Amide Imides. DFT Studies of Unusual α-SiMe3 Abstraction by an Amide Ligand

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

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Syntheses and Characterization of Tantalum Alkyl Imides and Amide Imides. DFT Studies of Unusual α-SiMe₃ Abstraction by an Amide Ligand