Complexes of tantalum with triaryloxides: Ligand and solvent effects on formation of hydride derivatives

Kawaguchi, Hiroyuki; Matsuo, Tsukasa

doi:10.1016/j.jorganchem.2005.05.002

Cited by 18 publications

(7 citation statements)

References 59 publications

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“…5 (c), in accordance with previous observations of Ti substituting for Ta in Ta/Ti oxides [25,26]. The TaTiO 2 ring fragments became The angle type distributions show clear variations between the two different coatings as discussed above and shown in Fig.…”

Section: Correlations Between Structural Parameters and Mechanical Losupporting

confidence: 91%

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Bassiri¹,

Evans²,

Borisenko³

et al. 2013

Acta Materialia

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can drop by as much as 40 % when it is doped with TiO 2 . We use a combination of electron diffraction data and atomic modeling using molecular dynamics to probe the atomic structure of these coatings, and examine the correlations between changes in the atomic structure and changes in the mechanical loss of these coatings. Our results show the first correlation between changes in the mechanical loss and experimentally measured changes in the atomic structure resulting from variations in the level of TiO 2 doping in TiO 2 doped Ta 2 O 5 coatings, in that increased homogeneity at the nearest neighbour level appears to correlate with reduced mechanical loss. It is demonstrated that subtle but measurable changes in the nearest neighbour homogeneity in an amorphous material

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Section: Correlations Between Structural Parameters and Mechanical Losupporting

confidence: 91%

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Bassiri¹,

Evans²,

Borisenko³

et al. 2013

Acta Materialia

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“…In the solid state (Fig. 3; Table 1), complex 3 is a six coordinate 'ate' complex with a K(DME) 3 + counterion coordinated to Cl(3); the K-Cl distance is 3.151(2) Å. X-ray crystal structures containing M-(μ-Cl)-K(DME) 3 linkages have not previously been reported, although comparable K-Cl distances are observed in 21 [Cp 3 Ho(μ-Cl)K(18-C-6)] [3.131 and 3.151 Å], 22 and [{κ 3 23 As a result of K(DME) 3 + 24 perhaps due to closer approach of the amido donors in the latter more flexible NON-donor ligand; U-N avg is 2.19 Å versus 2.30 Å in 3. However, a wide range of U IV -NR 2 bond distances have been reported, for example 2.18(2)-2.…”

Section: Uranium(iv) Xa 2 and Txa 2 Complexesmentioning

confidence: 93%

Rigid NON- and NSN-ligand complexes of tetravalent and trivalent uranium: comparison of U–OAr2 and U–SAr2 bonding

et al. 2012

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A rigid NSN-donor proligand, 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylthioxanthene (H(2)[TXA(2)], 1) was prepared by palladium-catalyzed coupling of 2,6-diisopropylaniline with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylthioxanthene. Deprotonation of 1 using (n)BuLi provided Li(2)(DME)(2)[TXA(2)] (2), and subsequent reaction with UCl(4) afforded [Li(DME)(3)][(TXA(2))UCl(3)] (4). The analogous NON-donor ligated complex [(XA(2))UCl(3)K(DME)(3)] [3; XA(2) = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene] was prepared by the reaction of K(2)(DME)(x)[XA(2)] with UCl(4). A cyclic voltammogram (CV) of 3 in THF/[NBu(4)][B(C(6)F(5))(4)] at 200 mV s(-1) showed an irreversible reduction to uranium(III) at E(pc) = -2.46 V versus FeCp(2)(0/+1), followed by a product wave at E(1/2) = -1.83 V. Complex 4 also underwent irreversible reduction to uranium(iii) [E(pc) = -2.56 V], resulting in an irreversible product peak at E(pa) = -1.83 V. One-electron reduction of complexes 3 and 4 using K(naphthalenide) under an argon atmosphere in DME yielded 6-coordinate [(XA(2))UCl(DME)] (5) and the thermally unstable 7-coordinate [(TXA(2))U(DME)Cl(2)Li(DME)(2)] (6), respectively. The U-S distances in 4 and 6 are uncommonly short, the C-S-U angles are unusually acute, and the thioxanthene backbone of the TXA(2) ligand is significantly bent. By contrast, the xanthene backbone in XA(2) complexes 3 and 5 is planar. However, κ(3)-coordination and an approximately meridional arrangement of the ancillary ligand donor atoms is maintained in all complexes. DFT and Atoms in Molecules (AIM) calculations were carried out on 3, 4, 5, 6, [(XA(2))UCl(3)](-) (3B), [(TXA(2))UCl(2)(DME)](-) (6B) and [(TXA(2))UCl(DME)] (6C) to probe the extent of covalency in U-SAr(2) bonding relative to U-OAr(2) bonding.

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“…For example, Wolczanski and co-workers have extensively studied the reactivity of Ta tetrahydride complexes prepared via the hydrogenolysis of low-valent Ta(III) siloxide precursors. 18−21 Similarly, Kawaguchi and co-workers have synthesized a series of group 5 polyhydrides via the reduction of Ta and Nb aryloxide chloride complexes with borohydride reagents; 22,23 several of these polyhydrides react spontaneously with N 2 gas to afford complexes featuring strongly reduced dinitrogen ligands. 24−26 In an effort to further develop the hydride route shown in Scheme 1 for the preparation of dinitrogen complexes, we have been examining new ligand systems that contain two amido units flanking a phosphine donor: i.e., NPN donor sets.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In addition to our own work, several other groups have investigated the potential applications of dinuclear group 5 polyhydrides as reductants for small molecules. For example, Wolczanski and co-workers have extensively studied the reactivity of Ta tetrahydride complexes prepared via the hydrogenolysis of low-valent Ta(III) siloxide precursors. − Similarly, Kawaguchi and co-workers have synthesized a series of group 5 polyhydrides via the reduction of Ta and Nb aryloxide chloride complexes with borohydride reagents; , several of these polyhydrides react spontaneously with N 2 gas to afford complexes featuring strongly reduced dinitrogen ligands. − …”

Section: Introductionmentioning

confidence: 99%

Hydrogenolysis of Tantalum Hydrocarbyl Complexes: Intermediates on the Road to a Dinuclear Tantalum Tetrahydride Derivative

2015

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The synthesis, characterization, and reactivity with H 2 of a series of tantalum hydrocarbyl complexes are reported. The reaction of [NPN*]TaMe 3 (4, where NPN* = PhP(2-(Nmesityl)-5-Me-C 6 H 3 ) 2 ) with dihydrogen (H 2 , 4 atm) results in the formation of the dinuclear tetrahydride ([NPN*]Ta) 2 (μ-H) 4 (5), without the observation of intermediates. The preparations of two alkyne benzyl complexes of the formula [NPN*]Ta(alkyne)-(CH 2 Ph) (where alkyne = BTA = bis(trimethylsilyl)acetylene ( 6), 3-hexyne ( 7)) are reported starting from the respective chloroalkyne complexes [NPN*]Ta(alkyne)Cl, by addition of benzylpotassium. Hydrogenation of these two alkyne benzyl complexes ultimately results in the formation of the same dinuclear tetrahydride 5; however, using lower pressures of H 2 and shorter reaction times results in the isolation of an intermediate in each case. Hydrogenation of 6 generates the alkene hydride complex [NPN*]Ta(trans-1,2-C 2 H 2 (SiMe 3 ) 2 )H (8); addition of H 2 to 7 gives [NPN*]Ta(1-hexene)H ( 9), in which the 3-hexyne moiety has been partially hydrogenated and isomerized to the 1-hexene regioisomer. Both of these alkene hydride complexes can be converted to the dinuclear tetrahydride complex 5 by addition of H 2 . A mechanism is proposed for the formation of the intermediates that involves hydrogenolysis of the alkyne moiety prior to the benzyl ligand; the formation of the trans-alkene units is suggested to be a result of a zwitterionic alkylidene intermediate that allows free rotation of a C−C single bond.

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Complexes of tantalum with triaryloxides: Ligand and solvent effects on formation of hydride derivatives

Cited by 18 publications

References 59 publications

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Rigid NON- and NSN-ligand complexes of tetravalent and trivalent uranium: comparison of U–OAr2 and U–SAr2 bonding

Hydrogenolysis of Tantalum Hydrocarbyl Complexes: Intermediates on the Road to a Dinuclear Tantalum Tetrahydride Derivative

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