Acidities of some fluorine substituted CH acids

Butin, K. P.; Kashin, A. N.; Beletskaya, I. P.; Герман, Л. С.; Polishchuk, V. R.

doi:10.1016/s0022-328x(00)86198-7

Cited by 54 publications

(17 citation statements)

References 7 publications

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“…For CHF 3 , p K a values of 26 – 31 have been experimentally determined in DMF, MeOH, and H 2 O . ], Quite unsurprisingly, no p K a data are available for [K(crypt‐222)] + , an extremely weak CH acid that is resistant to deprotonation even by very strong bases .…”

Section: Resultsmentioning

confidence: 99%

“…[39] 9 The acidity of toluenes is particularly sensitive to substituent effects. [45] 10 While no pK a data for CHF 3 has been reported in DMSO, the value of 26 has been obtained in DMF, [25] [26] another member of the family of aprotic dipolar solvents. Our estimate of pK a DMSO (DMSO % CHF 3 ) is based on this data as well as the fact that dimsyl in DMSO readily deprotonates CHF 3 at room temperature and even below.…”

Section: Is There a Way To Discern Between 1 And 2?mentioning

confidence: 99%

See 1 more Smart Citation

On the Structure of [K(crypt‐222)]⁺

Harlow¹,

Benet‐Buchholz

Miloserdov

et al. 2018

Helvetica Chimica Acta

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Due to disorder, [K(crypt‐222)]+ CF3− (1) is crystallographically indistinguishable from its isomer, a 1:1 fluoroform clathrate of deprotonated [K(crypt‐222)]+, [K(crypt‐222{‐H+})]·CHF3 (2). In our preceding publications, 1 was characterized on the basis of combined X‐ray diffraction, NMR, reactivity, labeling, acid‐base, and DFT studies. Herein we report that neither incorporation of deuterium nor any other transformation of [K(crypt‐222)]+ is observed in the presence of CD3OD/CD3OK at 70 °C or CD3S(O)CD2K/(D6)DMSO at 23 °C over hours and even days. Since fluoroform is easily and quickly deprotonated under such conditions, the demonstrated greater acidity of CHF3 relative to [K(crypt‐222)]+ provides additional evidence in favor of 1 and against 2. Likewise, crystal packing analysis and DFT calculations support 1, which has now been refined in the ultimately correct space group R32. Our previously drawn conclusions regarding [K(crypt‐222)]+ CF3− and the existence of a ‘naked’ trifluoromethyl anion in a condensed phase remain valid. The recent alternative refinement (Becker and Müller, Chem. Eur. J. 2017, 23, 7081 – 7086) of our raw diffraction data has been improperly performed in the wrong space group to yield a non‐charge‐balanced model [K(crypt‐222)]+·CHF3, which is hereby repudiated. Becker and Müller's attempts to resolve the charge balance issue have produced models that are inadequate from the perspective of both crystallography and chemistry.

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Section: Resultsmentioning

confidence: 99%

Section: Is There a Way To Discern Between 1 And 2?mentioning

confidence: 99%

On the Structure of [K(crypt‐222)]⁺

Harlow¹,

Benet‐Buchholz

Miloserdov

et al. 2018

Helvetica Chimica Acta

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“…Analogous reactions of bis (2,3,4,5-tetrafluorophenyl)mercury and DippFormH (mole ratio 1:2) with lanthanoid metals provided 6 La, 6 Nd and 6 Sm in good yield with N,N'-bis (2,6-diisopropylphenyl (8), isolated from trapping of a 3,4,5-trifluorobenzyne co-product. Oxidation and CÀF activation using this mercurial with reduced ortho-fluorine substitution is noteworthy, since the oxidation potentials of mercurials are enhanced by fluorine substitution [15] (e.g. Hg-A C H T U N G T R E N N U N G (C 6 F 5 ) 2 oxidises [YbCp 2 ] but HgPh 2 does not), [16] reactions of ytterbium with HgA C H T U N G T R E N N U N G (o-HC 6 F 4 ) 2 are much less clean than with HgA C H T U N G T R E N N U N G (C 6 F 5 ) 2 , [17] and CÀF activation of pentafluorobenzoic acid by [YbA C H T U N G T R E N N U N G (C 6 F 5 ) 2 ] [18] or [YbCp 2 ] [19] only removes one ortho-fluorine.…”

Section: Resultsmentioning

confidence: 99%

Steric Modulation of Coordination Number and Reactivity in the Synthesis of Lanthanoid(III) Formamidinates

Cole

Deacon

Forsyth

et al. 2007

Chemistry A European J

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Reactions of a range of the readily prepared and sterically tunable N,N'-bis(aryl)formamidines with lanthanoid metals and bis(pentafluorophenyl)mercury (Hg(C6F5)2) in THF have given an extensive series of tris(formamidinato)lanthanoid(III) complexes, [Ln(Form)3(thf)n], namely [La(o-TolForm)3(thf)2], [Er(o-TolForm)3(thf)], [La(XylForm)3(thf)], [Sm(XylForm)3], [Ln(MesForm)3] (Ln=La, Nd, Sm and Yb), [Ln(EtForm)3] (Ln=La, Nd, Sm, Ho and Yb), and [Ln(o-PhPhForm)3] (Ln=La, Nd, Sm and Er). [For an explanation of the N,N'-bis(aryl)formamidinate abbreviations used see Scheme 1.] Analogous attempts to prepare [Yb(o-TolForm)3] by this method invariably yielded [{Yb(o-TolForm)2(mu-OH)(thf)}2], but [Yb(o-TolForm)3] was isolated from a metathesis synthesis. X-ray crystal structures show exclusively N,N'-chelation of the Form ligands and a gradation in coordination number with Ln3+ size and with Form ligand bulk. The largest ligands, MesForm, EtForm and o-PhPhForm give solely homoleptic complexes, the first two being six-coordinate, the last having an eta1-pi-Ar--Ln interaction. Reaction of lanthanoid elements and Hg(C6F5)2 with the still bulkier DippFormH in THF resulted in C--F activation and formation of [Ln(DippForm)2F(thf)] (Ln=La, Ce, Nd, Sm and Tm) complexes, and o-HC6F4O(CH2)4DippForm in which the formamidine is functionalised by a ring-opened THF that has trapped tetrafluorobenzyne. Analogous reactions between Ln metals, Hg(o-HC6F4)2 and DippFormH yielded [Ln(DippForm)2F(thf)] (Ln=La, Sm and Nd) and 3,4,5-F3C6H2O(CH2)4DippForm. X-ray crystal structures of the heteroleptic fluorides show six-coordinate monomers with two chelating DippForm ligands and cisoid fluoride and THF ligands in a trigonal prismatic array. The organometallic species [Ln(DippForm)2(C[triple chemical bond]CPh)(thf)] (Ln=Nd or Sm) are obtained from reaction of Nd metal, bis(phenylethynyl)mercury (Hg(C[triple chemical bond]CPh)2) and DippFormH, and the oxidation of [Sm(DippForm)2(thf)2] with Hg(C[triple chemical bond]CPh)2, respectively. The monomeric, six-coordinate, cisoid [Ln(DippForm)2(C[triple chemical bond]CPh)(thf)] complexes have trigonal prismatic geometries and rare (for Ln) terminal C[triple chemical bond]CPh groups with contrasting Ln--C[triple chemical bond]C angles (Ln=Nd, 170.9(4) degrees; Ln=Sm, 142.9(7) degrees). Their formation lends support to the view that [Ln(DippForm)2F(thf)] complexes arise from oxidative formation and C--F activation of [Ln(DippForm)2(C6F5)] intermediates.

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“…Initial attempts with rare earth metals, triphenylbismuth, and some phenols failed, as did attempts in the present work between two Ln metals, BiPh 3 and 3,5‐di‐ tert ‐butylpyrazole (below). Accordingly, we turned to tris(pentafluorophenyl)bismuth since the electron withdrawing C 6 F 5 group should lower the reduction potential, as in the case with Hg(C 6 F 5 ) 2 versus HgPh 2 . This approach was tried despite the report of the failure of Ca, Sr, and Ba metals to undergo RTP reactions with Bi(C 6 F 5 ) 3 and HN(SiMe 3 ) 2 , since this low acidity substrate (p K a 26), undergoes RTP reactions with Yb/Sm and HgAr 2 , when Ar=Ph but not with Ar=C 6 F 5 , contrary to the normal relative reactivities of the mercurials in RTP reactions, which follow the reduction potentials …”

Section: Introductionmentioning

confidence: 99%

“…Accordingly, we turned to tris(pentafluorophenyl)bismuth since the electron withdrawing C 6 F 5 group should lower the reduction potential, as in the case with Hg(C 6 F 5 ) 2 versus HgPh 2 . This approach was tried despite the report of the failure of Ca, Sr, and Ba metals to undergo RTP reactions with Bi(C 6 F 5 ) 3 and HN(SiMe 3 ) 2 , since this low acidity substrate (p K a 26), undergoes RTP reactions with Yb/Sm and HgAr 2 , when Ar=Ph but not with Ar=C 6 F 5 , contrary to the normal relative reactivities of the mercurials in RTP reactions, which follow the reduction potentials

true 3 Ae + 2 BiPh_{3} + 6 LH \to 3 Ae (L)_{2} + 2 Bi + 6 PhH

…”

Section: Introductionmentioning

confidence: 99%

Can Bismuth Replace Mercury in Redox Transmetallation/Protolysis Syntheses from Free Lanthanoid Metals?

Guo

Blair

Deacon

et al. 2018

Chemistry A European J

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Tris(pentafluorophenyl)bismuth has been examined as a potential replacement for diarylmercurials in redox transmetallation/protolysis (RTP) syntheses of reactive rare earth compounds from free rare earth metals, HgAr2, and a proligand HL. Thus, the lanthanoid pyrazolates, [Ln(Ph2pz)3(thf)3] (Ph2pz=3,5‐diphenylpyrazolate; Ln=La, 1, Ce, 2, Nd, 3, Tb, 4; thf=tetrahydrofuran), [Ln2(Ph2pz)4(OMe)2(dme)2]⋅2 dme (Ln=Ho, 5, Er, 6, Tm, 7, Lu, 8; dme=1,2‐dimethoxyethane), [Ln(Ph2pz)3(dme)2] (Ln=Dy, 9, Sm, 10), [Ln(tBu2pz)3(thf)2] (tBu2pz=3,5‐di‐tert‐butylpyrazolate; Ln=La, 11, Ce, 12, Sm, 13, Gd, 14, Dy, 15, Ho, 16, Tm, 17, Yb, 18, Lu, 19), [Ln(ttfpz)3(thf)3] (ttfpz=3‐(2′‐thienyl)‐5‐(trifluoromethyl)pyrazolate; Ln=La, 20, Sm, 21), and [Er(PhMepz)3(thf)2] 22 (PhMepz=3‐phenyl‐5‐methylpyrazolate) have been prepared in good yields by redox transmetallation/protolysis reactions employing lanthanoid metals and trispentafluorophenylbismuth [Bi(C6F5)3]⋅0.5 diox (diox=1, 4‐dioxane) in donor solvents. This is a new and efficient synthetic route in which Bi(C6F5)3 replaces the commonly used Hg(C6F5)2 or HgPh2, and provides proof of concept for the method. [Ln2(Ph2pz)4(OMe)2(dme)2]⋅2 dme (5–8) complexes are derived from C−O bond activation of dme on crystallization of the initial products from this solvent, and are dimeric methoxide‐bridged species. Other structures are monomeric with η2‐bound pyrazolate ligands and nine‐coordinate metal atoms for complexes 1–4, 9–10 and 20–21, and eight‐coordinate metal atoms for complexes 11–19 and 22.

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Acidities of some fluorine substituted CH acids

Cited by 54 publications

References 7 publications

On the Structure of [K(crypt‐222)]⁺

On the Structure of [K(crypt‐222)]⁺

Steric Modulation of Coordination Number and Reactivity in the Synthesis of Lanthanoid(III) Formamidinates

Can Bismuth Replace Mercury in Redox Transmetallation/Protolysis Syntheses from Free Lanthanoid Metals?

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Acidities of some fluorine substituted CH acids

Cited by 54 publications

References 7 publications

On the Structure of [K(crypt‐222)]+

On the Structure of [K(crypt‐222)]+

Steric Modulation of Coordination Number and Reactivity in the Synthesis of Lanthanoid(III) Formamidinates

Can Bismuth Replace Mercury in Redox Transmetallation/Protolysis Syntheses from Free Lanthanoid Metals?

Contact Info

Product

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On the Structure of [K(crypt‐222)]⁺

On the Structure of [K(crypt‐222)]⁺