Ketone coordination chemistry of the diborane t-BuCH=C[B(C6F5)2]2

Reactions of the bifunctional borane t-BuCH=C[B(C6F5)2]2, 1, with simple Lewis bases were investigated to probe its Lewis acidity. Ethereal bases (Et2O, THF) bind very weakly, if at all, as no adducts were detectable in solution. Certain ketones, however, were observed to bind to 1. Acetone forms an adduct, 2, reversibly in solution (Keq at 293 K = 69.1), and the temperature dependence of this equilibrium yield thermodynamic parameters of H° = -59.5 ± 2.0 kJ mol-1; S° = -167 ± 4 J K-1 mol-1. Low temperature NMR spectroscopy suggests that the acetone binds to the more sterically accessible boron center trans to the t-Bu group. Ketone binding is strengthened when 2,3-diphenylcyclopropenone is reacted with 1, irreversibly forming an isolable adduct, 4, in high yield (95%). The availability of a resonance form incorporating the aromatic cyclopropenyl cation contributes to the added stability of this adduct in comparison to 2.Key words: organoboranes, diboranes, ketone complexes.

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A Pd4Br4macrocycle trapped by cocrystallization from a highly dynamic equilibrium of η3-cycloheptatrienide complexes

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229616008275 ◽

2016 ◽

Vol 72 (7) ◽

pp. 509-513 ◽

Cited By ~ 4

Author(s):

C. Jandl ◽

S. Stegbauer ◽

A. Pöthig

Keyword(s):

Coordination Chemistry ◽

Nmr Spectroscopy ◽

Low Temperature ◽

Dynamic Equilibrium ◽

Current Knowledge ◽

Complex Salt ◽

Common Motif ◽

Dimeric Compound

In the coordination chemistry of palladium, dimers bridgedviahalides are a common motif. Higher oligomers, however, are still rare. We report the structure of an alternating eight-membered [Pd4Br4]4−ring framed by cycloheptatrienide ligands, which was obtained by cocrystallization of dimers and tetramers of the complex salt bromido{η3-[3-(2,6-diisopropylphenyl)imidazolium-1-yl]cycloheptatrienido}palladium(II) tetrafluoroborate, namely bis[di-μ-bromido-bis({η3-[3-(2,6-diisopropylphenyl)imidazolium-1-yl]cycloheptatrienido}palladium(II))]cyclo-tetra-μ-bromido-tetrakis({η3-[3-(2,6-diisopropylphenyl)imidazolium-1-yl]cycloheptatrienido}palladium(II)) octakis(tetrafluoroborate) dichloromethane octasolvate, [Pd4Br4(C22H26N2)4][Pd2Br2(C22H26N2)2]2(BF4)8·8CH2Cl2. These dimers and tetramers form a highly dynamic equilibrium in solution which was studied by low-temperature NMR spectroscopy. In the light of the presented results, tetrameric PdIIspecies can be assumed to co-exist as a second species in many cases where by current knowledge only a dimeric compound would be expected.

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Nine-Vertex Polyhedral Monothiaborane Chemistry. The First nido Thianonaborane: Isolation and Characterization by NMR of the [nido-9-SB8H9]- Anion, and its Conversion to Compounds of the 6-L-arachno-4-SB8H10 Series (where L = SMe2 and Pyridine)

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19940367 ◽

1994 ◽

Vol 59 (2) ◽

pp. 367-373 ◽

Cited By ~ 5

Author(s):

Josef Holub ◽

John D. Kennedy ◽

Bohumil Štíbr

Keyword(s):

Nmr Spectroscopy ◽

Trifluoroacetic Acid ◽

Sodium Hydride ◽

High Yield ◽

Lewis Bases ◽

H Nmr ◽

Sodium Metal ◽

Isolation And Characterization

Deprotonation of 6(exo)-(SMe2)-arachno-4-SB8H10 either by sodium hydride or sodium metal leads to the isolation in high-yield of the [nido-9-SB8H9]- anion, which has been characterized by 11B and 1H NMR spectroscopy. The nido anion can be reconverted to compounds of the 6(exo)-L-arachno-4-SB8H10 series (where L = SMe2 and pyridine) by reaction with Lewis bases (L) followed by acidification with trifluoroacetic acid.

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Regioselectivity in SNH reactions of some 3-nitro-1,5-naphthyridines with chloromethyl phenyl sulfone

Canadian Journal of Chemistry ◽

10.1139/v04-001 ◽

2004 ◽

Vol 82 (5) ◽

pp. 567-570 ◽

Cited By ~ 5

Author(s):

Maria Grzegożek ◽

Barbara Szpakiewicz

Keyword(s):

Nmr Spectroscopy ◽

Nucleophilic Substitution ◽

Key Words ◽

High Yield ◽

Vicarious Nucleophilic Substitution ◽

H Nmr ◽

Phenyl Sulfone ◽

Convenient Synthesis ◽

Key Words 3 ◽

Hydrogen Substitution

3-Nitro-1,5-naphthyridine and its 2-substituted derivatives react with the carbanion of chloromethyl phenyl sulfone to give hydrogen-substitution products at position 4 in high yield. The intermediacy of 4-(phenylsulfonyl)chloromethyl σ adducts of 2-R-3-nitro-1,5-naphthyridines (R = H, D, Cl, OC2H5, NHCH3, OH) was established by 1H NMR spectroscopy. A convenient synthesis of 2-N-methylamino-3-nitro-1,5-naphthyridine is reported. Key words: 3-nitro-1,5-naphthyridines, anionic (phenylsulfonyl)chloromethyl σ adducts, vicarious nucleophilic substitution.

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Synthesis, characterization and chemistry of bis-(pentafluorophenyl)boryl ferrocene

Canadian Journal of Chemistry ◽

10.1139/v00-185 ◽

2001 ◽

Vol 79 (5-6) ◽

pp. 857-867 ◽

Cited By ~ 51

Author(s):

Bryon E Carpenter ◽

Warren E Piers ◽

Masood Parvez ◽

Glenn PA Yap ◽

Steven J Rettig

Keyword(s):

Solid State ◽

Lewis Acids ◽

Charge Transfer Band ◽

Lewis Acidity ◽

Ferrocene Derivatives ◽

X Ray ◽

Lewis Bases ◽

X Ray Crystallography ◽

Boron Center ◽

Iron Center

Bis-(pentafluorophenyl)boryl ferrocene, 1, was prepared via borylation of ferrocene with HB(C6F5)2 or via a transmetallation reaction involving FcHgCl and ClB(C6F5)2 in 8791% yield. The compound is characterized by a deep maroon colour. A significant intramolecular ironboron interaction is manifested in the solution spectroscopic (Fe [Formula: see text] B charge transfer band at ~230 nm, ε = 1.33 × 104) and solid-state crystallographic data (Fe-B = 2.924 Å) This interaction has an impact on the Lewis acidity of the boron center which, unlike the related compound B(C6F5)3, does not strongly bind Lewis bases such as acetone, THF, or acetonitrile. However, an adduct between the stronger base PMe3 and 1 forms readily and this complex (2) was fully characterized. The electron withdrawing -B(C6F5)2 group causes 1 to be oxidized at +450 mV relative to ferrocene. Oxidation of 1 with [NO][BF4], AgOSO2CF3, or AgC6F5 leads to the zwitterionic ferrocenium borates 3-F, 3-OTf, and 3-C6F5, respectively. Each of these compounds was characterized spectroscopically and via X-ray crystallography. The properties of these compounds relative to 1 suggest that oxidation of the iron center significantly enhances the Lewis acidity of the boron center. Due to the σ-donating ability of the borate substituents, zwitterions 3 are weaker oxidizing agents than unsubstituted ferrocenium salts.Key words: organoboranes, ferrocene derivatives, Lewis acids.

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Ten-Vertex Polyhedral Monocarbaborane Chemistry. The Novel High-Yield Formation of the Ten-Vertex closo Compound [6-(PMe2Ph)-closo-1-CB9H9] from the Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11]

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19932924 ◽

1993 ◽

Vol 58 (12) ◽

pp. 2924-2935 ◽

Cited By ~ 8

Author(s):

Jane H. Jones ◽

Bohumil Štíbr ◽

John D. Kennedy ◽

Mark Thornton-Pett

Keyword(s):

Nmr Spectroscopy ◽

Diffraction Analysis ◽

High Yield ◽

Monoclinic Space Group ◽

The Novel ◽

X Ray Diffraction ◽

Metal Centre ◽

X Ray ◽

Yield Formation ◽

Boiling Toluene

Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] in boiling toluene solution results in an elimination of the platinum centre and cluster closure to give the ten-vertex closo species [6-(PMe2Ph)-closo-1-CB9H9] in 85% yield as a colourles air stable solid. The product is characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from hexane-dichloromethane) are monoclinic, space group P21/c, with a = 903.20(9), b = 1 481.86(11), c = 2 320.0(2) pm, β = 97.860(7)° and Z = 8, and the structure has been refined to R(Rw) = 0.045(0.051) for 3 281 observed reflections with Fo > 2.0σ(Fo). The clean high-yield elimination of a metal centre from a polyhedral metallaborane or metallaheteroborane species is very rare.

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The Microscopic Structure Of Shallow Donors In Silicon Carbide

MRS Proceedings ◽

10.1557/proc-442-619 ◽

1996 ◽

Vol 442 ◽

Author(s):

J.-M. Spaeth ◽

S. Greulich-Weber ◽

M. März ◽

E. N. Kalabukhova ◽

S. N. Lukin

Keyword(s):

High Temperature ◽

Low Temperature ◽

Temperature Dependence ◽

Double Resonance ◽

Epr Spectra ◽

Electron Nuclear Double Resonance ◽

Paramagnetic Resonance ◽

Vacancy Pair ◽

Temperature Spectra ◽

Electron Paramagnetic

AbstractThe electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.

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