Formation of 5-membered metallacycles at iPrPCPIr by C–H, O–H, and C–CO bond cleavage

Wilklow-Marnell, Miles; Brennessel, William W.; Jones, William D.

doi:10.1016/j.poly.2016.03.018

Cited by 9 publications

(12 citation statements)

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“…The even longer reaction times noted under extremely dry conditions in Teflon lined NMR tubes indicates that other O-H sources such as water or Si-OH functionalities of glass may play a role as well. In any case, once III is formed, both routes follow the same course of isomerization to V , consistent with our previous findings with benzophenone …”

Section: Resultssupporting

confidence: 92%

“…Within 10–20 min after combining reactants, 31 P NMR spectroscopy showed the major product to be a singlet at δ 46.4 (>50%), and the 1 H NMR spectrum exhibited a hydride triplet at δ −9.25. These chemical shifts are very similar to our previous results with benzophenone, suggesting the product is the trans C–H activation product iPr PCPIr(κ-O,C-OC(C 6 H 4 )(C 6 F 5 ))H (Scheme ). In further corroboration, 3 new signals were observed by 19 F NMR spectroscopy consistent with an unaffected C 6 F 5 moiety, though the para -F was largely obscured by excess BP-F 5 .…”

Section: Resultssupporting

confidence: 89%

“…The chemical shift of this hydride, and slow conversion of III to V , is consistent with the assignment of III as the trans C–H isomer of V (Scheme ). As shown in previous work, , C–H oxidative addition of aryl C–H bonds to R PCPIr is not directing group assisted, and instead a cyclometalated trans C–H species is formed first, followed by slow isomerization to the cis C–H complex.…”

Section: Resultssupporting

confidence: 60%

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C(sp²)–F Oxidative Addition of Fluorinated Aryl Ketones by ^iPrPCPIr

2017

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The reaction of iPr PCPIrH 4 ( iPr PCP = κ 3 -2,6-C 6 H 3 (CH 2 P( i Pr) 2 ) 2 ) with ≥2 equiv of 2,3,4,5,6-pentafluoroacetophenone (AP-F5) in aromatic solvents at room temperature leads to the hydrogenation of AP-F5 and formation of the corresponding 5-coordinate alkoxy hydride species (I) within several minutes. Heating at ≥120 °C quickly provides the cyclometalated trans C-H product iPr PCPIr(κ-O,C-OC 8 H 3 F 4 )H (III), which slowly isomerizes to the cis C-H product iPr PCPIr(κ-C,O-OC 8 H 3 F 4 )H (V). The fate of the fluoride during formation of III and V is not entirely clear, though the production of HF is implicated by significant glass etching and several crystal structures. When iPr PCPIrH 4 is allowed to react overnight with ≥2 equiv of AP-F5 at room temperature, formation of C−F oxidative addition product iPr PCPIr(κ-O,C-OC 8 H 3 F 4 ) F (II) is observed by 31 P and 19 F NMR spectroscopy. When iPr PCPIrH 4 activated with tert-butylethylene is employed, formation of II occurs within 10 min. Analogous reactivity is observed with several other fluorinated aryl ketones, and the crystal structure of the C−F oxidative addition product of 2,6-difluoroacetophenone (II AF2 ) has been determined. This represents the first welldefined examples of stable iridium fluorides formed by C(sp 2 )−F oxidative addition.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 89%

Section: Resultssupporting

confidence: 60%

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C(sp²)–F Oxidative Addition of Fluorinated Aryl Ketones by ^iPrPCPIr

2017

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“…Additional NBE acceptor (2 equiv) was added, and after an additional 24 h at ambient temperature, the 31 P NMR spectrum showed only a single resonance at δ 42.5 ppm and complete disappearance of any hydride resonances. The NMR data are consistent with cyclometalation to afford product 4 (eq ), which has been previously identified (and crystallographically characterized) as the product of biphenylene C–C bond addition to ( tBu PCP)Ir. , …”

Section: Resultssupporting

confidence: 80%

“…( iPr4 PCP)Ir(propene) (50 mM) reacted over ca. 25 h in p -xylene- d 10 with biphenyl (50 mM) to give the previously characterized , cyclometalated complex 5 (eq ). The reaction with biphenyl in higher concentration (260 mM) proceeded significantly more rapidly (10 mM after 30 min and 50 mM after 12 h), but at an even higher biphenyl concentration (520 mM) the rate of the reaction was unchanged.…”

Section: Resultsmentioning

confidence: 99%

Single and Double C–H Activation of Biphenyl or Phenanthrene. An Example of C–H Addition to Ir(III) More Facile than Addition to Ir(I)

et al. 2016

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Experimental: General methods and CompoundsGeneral Experimental Methods. All reactions, recrystallizations, and routine manipulations were performed at ambient temperature under argon atmosphere using an argon--filled glove box or by using standard Schlenk techniques. Reagent grade solvents were distilled from sodium/potassium alloy and degassed with argon. Norbornene was purified by sublimation. All deuterated NMR solvents were dried, vacuum--transferred, and stored in an argon--filled glovebox. 1 H and 31 P{ 1 H} NMR spectra were obtained on 400--MHz or 500 MHz Varian spectrometers. 1 H NMR chemical shifts are reported in ppm downfield from tetramethylsilane and were referenced to residual protiated ( 1 H) or deuterated solvent. 31 P{ 1 H} NMR chemical shifts are reported in ppm and were referenced to 85% H3PO4 or a capillary tube containing the external standard Me3P in mesitylene--d12 solvent (δ --62.0 ppm). The compounds tBu4 PCPIrH2 and iPr4 PCPIr(C2H4) were prepared as described in the literature. 14--18 ( tBu4 PCP)Ir(H)(C14H9) (1) tBu4 PCPIrH2 (5.9 mg, 0.010 mmol) was dissolved in 0.5 mL of mesitylene--d12 in a J--Young NMR tube at room temperature, and 2 equivalents of norbornene were added from a stock solution in p--xylene. Phenanthrene (1.1 eq; 0.011 mmol) was added to the resulting solution; after stirring for one minute, the dark red--orange solution turned bright orange. NMR spectra indicate the presence of multiple isomers/rotamers resulting from C--H oxidative addition. 31

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Pincer‐Metal Complexes as Catalysts for CH Activation and Functionalization in Organic Synthesis

Reyes-Sánchez¹,

González‐Sebastián²,

Morales‐Morales³

2022

Handbook of CH-Functionalization

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This article describes applications of pincer complexes in the CH bond activation and functionalization. The reader is provided with an overview of this important area and its crucial role in forging stoichiometric intra‐ and intermolecular CH activations in organometallic pincer compounds. A special emphasis is given to the role of pincer ligands in promoting challenging CH activation methods. Applications in the stoichiometric and catalytic formation of CC and CB bonds via CH activation in organic substrates are also presented. The scope of this article is limited to complexes of late transition metals and therefore, reactions involving main group metals are not included.

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Formation of 5-membered metallacycles at iPrPCPIr by C–H, O–H, and C–CO bond cleavage

Cited by 9 publications

References 42 publications

C(sp²)–F Oxidative Addition of Fluorinated Aryl Ketones by ^iPrPCPIr

C(sp²)–F Oxidative Addition of Fluorinated Aryl Ketones by ^iPrPCPIr

Single and Double C–H Activation of Biphenyl or Phenanthrene. An Example of C–H Addition to Ir(III) More Facile than Addition to Ir(I)

Pincer‐Metal Complexes as Catalysts for CH Activation and Functionalization in Organic Synthesis

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Formation of 5-membered metallacycles at iPrPCPIr by C–H, O–H, and C–CO bond cleavage

Cited by 9 publications

References 42 publications

C(sp2)–F Oxidative Addition of Fluorinated Aryl Ketones by iPrPCPIr

C(sp2)–F Oxidative Addition of Fluorinated Aryl Ketones by iPrPCPIr

Single and Double C–H Activation of Biphenyl or Phenanthrene. An Example of C–H Addition to Ir(III) More Facile than Addition to Ir(I)

Pincer‐Metal Complexes as Catalysts for CH Activation and Functionalization in Organic Synthesis

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C(sp²)–F Oxidative Addition of Fluorinated Aryl Ketones by ^iPrPCPIr

C(sp²)–F Oxidative Addition of Fluorinated Aryl Ketones by ^iPrPCPIr