Synthesis and crystallographic characterization of a dinuclear 1,2-hydrazido(2-) complex of tungsten(VI), [W(.eta.5-C5Me4(CMe3))(CCMe3)I]2(.mu.-N2H2).CH2Cl2

Churchill, Melvyn Rowen; Li, Yong Ji; Blum, Lauren.; Schrock, Richard R.

doi:10.1021/om00079a020

Cited by 32 publications

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“…Similar W(VI)-alkylidynes featuring WuC t Bu groups, all exhibit a nearly linear ∠WuC-C angle, ranging between 170-175°. [1][2][3]8,30,32,[38][39][40] The closest evidence for a high valent W-alkylidyne that shows significant deviation in its ∠WuC-C angle is the complex CpWuCAd(CH 2 t Bu) 2 reported by Schrock; 41 this complex, bearing an adamantyl unit on the WuC α features an acute ∠WuC-C angle of 166.2 (6)°. The complexes TpWuC t Bu(NHPh) 2 (Boncella et al; ∠WuC-C angle = 166.5(4)°) 42 and Tp*WuCPh(Br) 2 (McCleverty et al; ∠WuC-C angle = 168.0(8)°) 43 also exhibit ∠WuC-C angles that deviate significantly from linearity.…”

Section: Resultsmentioning

confidence: 93%

A new ONO³⁻ trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

et al. 2015

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This report details the synthesis and characterization of the semi-flexible [ON(CH2)O]H3 (1) ligand and its W(vi)-alkylidene and alkylidyne complexes. The alkylidyne complex [ONH(CH2)O]W[triple bond, length as m-dash]C(t)Bu(O(t)Bu) (2) forms as a result of alcoholysis of 1 with ((t)BuO)3W[triple bond, length as m-dash]C(t)Bu. Complex 2 evolves to [ON(CH2)O]W[double bond, length as m-dash]CH(t)Bu(O(t)Bu) (3) through proton migration from the N atom of the pincer ligand to the W[triple bond, length as m-dash]Cα bond. Deprotonation of 2 or 3 with Ph3PCH2 affords the anionic alkylidyne {CH3PPh3}{[ON(CH2)O]W[triple bond, length as m-dash]C(t)Bu(O(t)Bu)} (4). Complex 4 exhibits pincer-ligand-centered reactivity with electrophiles (H(+), Me(+), and TMS(+)), in spite of its enhanced inorganic enamine interaction. Addition of 2 equiv. of HCl to 4 yields the W(vi)-neopentyl complex [ON(CH2)O]W(CH2(t)Bu)(O(t)Bu)(Cl) (5). MeOTf or TMSOTf addition to 4 generates the dianionic pincer ligated alkylidynes [ONR(CH2)O]W[triple bond, length as m-dash]C(t)Bu(O(t)Bu) (R = Me (6-Me); TMS (6-TMS)). Complexes 2-5 were characterized by multinuclear NMR spectroscopy, and combustion analysis. Complexes 4 and 5 were also characterized by single crystal X-ray diffraction. This work bridges the gap in the series involving W(vi)-alkylidynes ligated to the rigid [CF3-ONO](3-), and the flexible [O(CH2)N(CH2)O](3-) ligands. DFT computations permit comparison of the inorganic enamine effect within alkylidynes supported by all three trianionic-pincer type ONO ligands.

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Section: Resultsmentioning

confidence: 93%

A new ONO³⁻ trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

et al. 2015

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“…The stability of a metallacyclobutadiene relative to the alkylidyne precursor is dependent on a combination of steric and electronic contributors. [33][34][35] Schrock and co-workers first demonstrated that poorly basic ancillary ligands stabilize metallacyclobutadienes. [33][34][35] Some relevant examples are the tungstenacyclobutadiene W(κ 2 -C 3 R 3 )(OR) 3 with weakly basic alkoxides -OC(CF 3 ) 2 CH 3 , 35 -OCH(CF 3 ) 2 , 35 and -OC 6 H 3 ( i Pr) 2 .…”

Section: Introductionmentioning

confidence: 99%

Unusually stable tungstenacyclobutadienes featuring an ONO trianionic pincer-type ligand

et al. 2013

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This report presents the synthesis of the first neutral trianionic ONO pincer-type tungsten alkylidyne complex, [CF(3)-ONO]W≡C((t)Bu)(OEt(2)) (5) {where CF(3)-ONO = (MeC(6)H(3)[C(CF(3))(2)O])(2)N(3-)}. Treating 5 with 1-phenylpropyne, 4,4-dimethyl-2-pentyne, and cyclooctyne yields the corresponding tungstenacyclobutadiene complexes [CF(3)-ONO]W[κ(2)-C((t)Bu)C(Me)C(Ph)] (6), [CF(3)-ONO]W[κ(2)-C((t)Bu)C(Me)C((t)Bu)] (7), and [CF(3)-ONO]W[κ(2)-C((t)Bu)C(CH(2))(6)C] (8). Complexes 6, 7, and 8 do not undergo retro-[2 + 2]-cycloaddition even at 200 °C or in the presence of PMe(3). DFT methods to elucidate the electronic structure of complexes 5 and 6 reveal important electronic factors that contribute to the lack of reactivity for the tungstenacyclobutadienes. An important bonding combination between the pincer N-atom lone pair and the W[triple bond, length as m-dash]C bond within 5, termed an inorganic enamine, provides an explanation for the lack of retro-[2 + 2]-cycloaddition from 6, 7, and 8. (15)N NMR spectroscopy was used to confirm the computational finding of an inorganic enamine bonding combination. Single crystal X-ray analysis of 5, 6, 7, and 8 provides insight into possible steric inadequacies within the CF(3)-ONO(3-) ligand to promote catalytic metathesis.

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“…The latter complex is unique in that combined structural, spectroscopic, and DFT calculations suggest that the bridging ‘diazene’ is best formulated as N 2 H 2 2- . While this level of diazene activation has been observed in complexes of highly reducing early transition metals [9] it is not well established for the later transition metals, including iron. [7, 10] One-electron reduction of the [Fe 2 (μ-N 2 H 2 )] 2+ complex furnishes the EPR-active mixed-valent [Fe 2 (μ-N 2 H 2 )] 1+ complex, whose electronic structure characterization by combined EPR/ENDOR spectroscopy is described.…”

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confidence: 99%

“…[12] For example, 3 J (H,H) = 28.0 Hz for [(CO) 5 Cr] 2 ( trans -μ-N 2 H 2 ), [13] which has an N-N bond distance of 1.25 Å, [14] while 3 J (H,H) = 9.4 Hz for [(η 5 -C 5 Me 4 H) 2 ZrI] 2 ( trans -μ-N 2 H 2 ), which has an N-N bond distance of 1.414(3) Å. [9b] Hence, the observed 3 J (H,H) coupling in 3 is most consistent with a single bond.…”

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confidence: 99%

Transformation of an [Fe(η²‐N₂H₃)]⁺Species to π‐Delocalized [Fe₂(μ‐N₂H₂)]^2+/+Complexes

Saouma¹,

Kinney²,

Hoffman³

et al. 2011

Angew Chem Int Ed

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A monomeric iron Fe(η2-N2H3) species has been prepared, and exposure to oxygen yields a diiron complex that features five-coordinate iron centers and an activated bridging diazene ligand (NH=NH). Combined structural, theoretical, and spectroscopic data for the redox pair of complexes [Fe2(μ-N2H2)]2+/1+ are consistent with 4-center, 4-electron π-delocalized bonding picture across the Fe-NH-NH-Fe core that finds analogy in butadiene and the butadiene anion.

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Synthesis and crystallographic characterization of a dinuclear 1,2-hydrazido(2-) complex of tungsten(VI), [W(.eta.5-C5Me4(CMe3))(CCMe3)I]2(.mu.-N2H2).CH2Cl2

Cited by 32 publications

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A new ONO³⁻ trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

A new ONO³⁻ trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

Unusually stable tungstenacyclobutadienes featuring an ONO trianionic pincer-type ligand

Transformation of an [Fe(η²‐N₂H₃)]⁺Species to π‐Delocalized [Fe₂(μ‐N₂H₂)]^2+/+Complexes

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Synthesis and crystallographic characterization of a dinuclear 1,2-hydrazido(2-) complex of tungsten(VI), [W(.eta.5-C5Me4(CMe3))(CCMe3)I]2(.mu.-N2H2).CH2Cl2

Cited by 32 publications

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A new ONO3− trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

A new ONO3− trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

Unusually stable tungstenacyclobutadienes featuring an ONO trianionic pincer-type ligand

Transformation of an [Fe(η2‐N2H3)]+Species to π‐Delocalized [Fe2(μ‐N2H2)]2+/+Complexes

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A new ONO³⁻ trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

A new ONO³⁻ trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

Transformation of an [Fe(η²‐N₂H₃)]⁺Species to π‐Delocalized [Fe₂(μ‐N₂H₂)]^2+/+Complexes