Steric engineering of C–F activation with lanthanoid formamidinates

Cole, Marcus L.; Deacon, Glen B.; Junk, Peter Courtney; Konstas, Kristina

doi:10.1039/b419047e

Cited by 71 publications

(146 citation statements)

References 32 publications

Supporting

Mentioning

124

Contrasting

Unclassified

Order By: Relevance

“…Only one tris(formamidinato)lanthanoid(III) complex has been reported previously, namely, [Sm(DippForm) 3 ], (DippFormH= N,N ′ ‐ bis(2,6‐diisopropylphenyl)formamidine), which was prepared unexpectedly by solvent induced rearrangement of [Na(thf) 5 ][Sm(DippForm) 2 I 2 (thf)] 8…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…In preliminary studies we have successfully prepared [La(DippForm) 2 F(thf)] from elemental lanthanum, Hg(C 6 F 5 ) 2 and the bulky N,N ′ ‐ bis(aryl)formamidine DippFormH,10 and shown that the samarium analogue can be accessed from the divalent precursor [Sm(DippForm) 2 (thf) 2 ] and Hg(C 6 F 5 ) 2 in THF [Eq. ()] 8. This highlights the steric influence of the donor solvent (THF), which further frustrates the final protolysis, contrary to the aforementioned redistribution of [Na(thf) 5 ][Sm(DippForm) 2 I 2 (thf)] to [Sm(DippForm) 3 ] and [SmI 3 (thf) 3.5 ] upon dissolution in toluene.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Cole

Deacon

Forsyth

et al. 2007

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Cole

Deacon

Forsyth

et al. 2007

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

show abstract

“…(2,6-di-iso-propylphenyl)formamidine) was observed at +150.2 ppm. 47 The broad nature of the 19 F signal is probably due to the fast exchange between two bridging fluorides as well as to coupling with the metal ions. Because of the line broadening, we were not able to determine the coupling constant between the 19 F and 89 Y nuclei.…”

Section: Resultsmentioning

confidence: 99%

“…[43][44] Deacon and co-workers gradually expanded the synthesis of lanthanide fluorides with different ancillary ligands by means of C-F bond activation. [45][46][47][48][49] Andersen, Eisenstein, and Maron conducted experimental and computational studies on the C-F activation reaction by Cp 36,42 and showed that while the reaction outcome was hydrogen for fluorine exchange, it did not follow a simple σ-bond metathesis mechanism (Scheme 1b). [37][38] Follow-up studies suggested a more complicated mechanism might be in play due to the large difference in charge distribution between starting materials and products.…”

Section: Introductionmentioning

confidence: 99%

Aromatic C–F Bond Activation by Rare-Earth-Metal Complexes

Huang

Diaconescu

2016

Organometallics

View full text Add to dashboard Cite

C-F bond activation is a challenging reaction with increasing importance in synthesis. The strength of the C-F bond and the shielding effect of the fluorine atom render its activation difficult. Rare-earth metals offer an exceptional opportunity for this process because the high dissociation energy of the M-F bond offsets the strength of the C-F bond. Herein we report a unique reaction for the C-F activation of aromatic bonds by rare-earth metal complexes. The strong C-F bond of perfluorobenzene is cleaved under reducing conditions in the presence of a rare-earth metal iodide to form initially an equimolar mixture of a metal fluoride and a metal perfluorophenyl complex; the latter eventually undergoes β-F elimination to a metal fluoride. A similar reactivity is observed when reacting inverse sandwich rare-earth metal arene complexes with perfluorobenzene. All compounds were characterized by X-ray crystallography, multi-nuclear NMR spectroscopy, and elemental analysis.

show abstract

Stabilization of Aryl–Calcium, –Strontium, and –Barium Compounds by Designed Steric and π‐Bonding Encapsulation

et al. 2005

Self Cite

View full text Add to dashboard Cite

In the last decade a major theme of organometallic chemistry has been the design and development of alternative ligand systems capable of stabilizing monomeric metal complexes while provoking novel reactivity. Exploration of this field is driven by the potential use of these complexes in catalysis and organic synthesis. Examples of monoanionic chelating Ndonor ligands that have received much recent attention (Scheme 1) include the b-diketiminate (I) [1] and the amidinate (II) [2] ligand systems. Much less attention has been given to the closely related triazenides (III). [3, 4] This may be attributed to the lack of suitable ligands that are sterically crowded enough to prevent undesirable ligand redistribution reactions and allow better control of the electronic and steric properties at the metal center.Triazenides are weaker donors than the isoelectronic amidinates and the related b-diketiminates, and should induce greater electrophilicity at a bonded metal atom. [5] This is reflected by the results of an NBO (natural bond orbitals) analysis of the energy-minimized structures [6] of the model anions 1,3-diphenyl-1,3-diketiminate (I M ), 1,3-diphenyl-1,3-diazaallyl (II M ), and 1,3-diphenyltriazenide (III M ) (see Supporting Information), which shows an NPA (natural population analysis) charge for the chelating N atoms of À0.54, À0.60, and À0.38, respectively.We recently succeeded in the preparation of aryl-substituted, sterically crowded triazenes. Ligands of this type may be synthesized in excellent yields by the reaction of different substituted 2-lithiobiphenyls with the m-terphenyl azide 1, followed by hydrolysis (Scheme 2).In a first attempt to test their properties, we have used the obtained triazenes to stabilize pentafluorophenyl compounds of the heavier alkaline-earth metals calcium, strontium, and barium. The heteroleptic pentafluorophenyl triazenides are accessible in tetrahydrofuran as solvent by a convenient onepot transmetalation/deprotonation [7] reaction from the triazene 2 a (HN 3 ArAr'), bis(pentafluorophenyl)mercury, and the corresponding alkaline-earth metal (Scheme 3). After crystallization from n-heptane, either the THF-free compounds [M(C 6 F 5 )(N 3 ArAr')] (M = Sr (4), Ba (5)) or the solvate [Ca(C 6 F 5 )(N 3 ArAr')(thf)] (3) were isolated in good yields. It is remarkable that attempts to replace the pentafluorophenyl substituents by a second triazenide ligand have not been successful so far. Apparently, the steric bulk of the latter prevents further substitution or ligand redistribution and therefore formation of the homoleptic complexes. [8] Solutions of 4 or 5 in aromatic or aliphatic solvents show considerable thermal stability and can be stored at ambient

show abstract

Steric engineering of C–F activation with lanthanoid formamidinates

Abstract: Reaction of lanthanum with Hg(C6F5)2 and bulky N,N'-bis(2,6-diisopropylphenyl)formamidine (HDippForm) in tetrahydrofuran gives [LaF{DippForm}2(THF)] with a rare terminal Ln-F bond, and a high yield of a novel functionalized formamidine, DippForm((CH2)4OC6F4H-o).

Cited by 71 publications

References 32 publications

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

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

Aromatic C–F Bond Activation by Rare-Earth-Metal Complexes

Stabilization of Aryl–Calcium, –Strontium, and –Barium Compounds by Designed Steric and π‐Bonding Encapsulation

Contact Info

Product

Resources

About