Recent Findings in Cyclometallation of meta-Substituted Aryl Ligands by Platinum Group Metal Complexes by Caryl–R Bond Activation (R=H, CR3, SiR3)

Steenwinkel, Pablo; Gossage, Robert A.; Koten, Gerard van

doi:10.1002/(sici)1521-3765(19980515)4:5<759::aid-chem759>3.3.co;2-b

Cited by 17 publications

(36 citation statements)

References 16 publications

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“…metalation at the aryl C-3 position) is accomplished by these synthetic protocols. 7 The 1 H NMR spectrum of a solution of 2 (C 6 D 6 , room temperature) reveals singlet resonances for both the oxazoline methyl groups and ring methylene protons (δ 1.17 and 3.70 ppm, respectively). The Sn-Me groups are centered at δ 0.46 ppm, with the diagnostic 117 Sn/ 119 Sn satellites ( 2 J H-Sn ) 26.7, 27.8 Hz) confirming the presence of the SnMe 3 group.…”

Section: Resultsmentioning

confidence: 99%

“…Following the same procedure, Et3N (65 µL, 0.47 mmol) was added to the mixture and 1 H and 7 Li{ 1 H} spectra were recorded of the mixture at room temperature. No change was observed in the chemical shift of the 7 Li signal for 3a. the presence of higher lattice symmetry.…”

Section: Synthesis Of [Li(iprh-phebox)]2 (3b)mentioning

confidence: 92%

“…1 H and 13 C{ 1 H} NMR spectra were recorded on a Varian Inova 300 spectrometer. 7 Li NMR (5 mm tube) and NMR experiments with diethyl ether, tetrahydrofuran, and triethylamine (10 mm tube) were recorded on a Varian Mercury 200 spectrometer. Benzene-d 6 and toluene-d8 were purchased from Cambridge Isotope Laboratories, distilled from Na, and stored in a nitrogen-filled M. Braun glovebox.…”

Section: Methodsmentioning

confidence: 99%

“…Both 1 H and 7 Li NMR signals of 3a are insensitive to the addition of 1 equiv of diethyl ether, THF, or triethylamine. This suggests that the dimeric structure is not disrupted by these simple bases, and hence, stronger coordination of the bis(oxazoline) substituents is implied.…”

Section: Scheme 2 Synthesis Of [Li(rr′-phebox)] Complexesmentioning

confidence: 99%

“…After the NMR spectra were recorded without additional coordinating solvents present, the NMR tube was placed under nitrogen in a modified Schlenk tube and Et 2O (45 µL, 0.46 mmol) was added. 1 H, 7 Li{ 1 H}, and 13 C{ 1 H} NMR spectra were recorded at room temperature and 1 H and 7 Li{ 1 H} NMR spectra at -60°C…”

Section: Synthesis Of [Li(iprh-phebox)]2 (3b)mentioning

confidence: 99%

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Synthesis and Structural Characterization of Lithium and Trimethyltin Complexes of 2,6-Bis(oxazolinyl)phenyl

et al. 2005

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The treatment of 2,6-bis(oxazolinyl)phenyl bromide (Phebox-Br) with n-BuLi affords a Phebox-Li complex. Subsequent transmetalation with [SnClMe 3 ] affords a Phebox-Sn complex. The Phebox ligand can coordinate to a transition metal in various terdentate fashions; both the oxazoline oxygen and the imine nitrogen are perfectly positioned for chelation; "NCN", "OCO", or mixed terdentate coordination modes are theoretically possible using this ligand. The structural properties and NMR spectra of [Sn(Me,Me-Phebox)Me 3 ] (2) and [Li(R,R′-Phebox)] complexes 3a (R ) R′ ) Me), 3b (R ) iPr, R′ ) H), and 3c (R ) tBu, R′ ) H) were investigated. It was found that 2 exhibits no chelation of the Phebox ligand to the Sn center in this case. The [Li(R,R′-Phebox)] complex 3a has been crystallographically characterized and is in the form of a molecular dimer (i.e. [Li(Phebox)] 2 ), containing two formally three-center-two-electron bonds in a four-membered Li 2 C 2 ring. The formal Phebox anion is bonded to the lithium cation via the two ortho imine N centers and the intraannular aromatic C atom. The 13 C{ 1 H} NMR signal of C ipso , being a seven-line pattern with coupling constant 1 J( 13 C-7 Li) ) 18 Hz, confirms that the dimeric structure is maintained in solution at room temperature. Variable-temperature (VT) NMR studies of 3a indicate that a fluxional process is occurring at room temperature, which can be frozen out below -16°C (∆G q ) 56 kJ/mol). This fluxional process is not observed in VT-NMR studies on 3b,c. This is likely due to the presence of bulky (iPr or tBu) substituents that effectively shut down the pathways to rapid inversion of the puckering of the five-membered chelate ring.

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Section: Resultsmentioning

confidence: 99%

Section: Synthesis Of [Li(iprh-phebox)]2 (3b)mentioning

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Section: Scheme 2 Synthesis Of [Li(rr′-phebox)] Complexesmentioning

confidence: 99%

Section: Synthesis Of [Li(iprh-phebox)]2 (3b)mentioning

confidence: 99%

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Synthesis and Structural Characterization of Lithium and Trimethyltin Complexes of 2,6-Bis(oxazolinyl)phenyl

et al. 2005

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Inter- versus Intramolecular C−H Activation: Synthesis and Characterization of a Novel Platinum-Carbene Complex

Cave

Hallett

Errington

et al. 1998

Angewandte Chemie International Edition

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Coordination Chemistry of SCS PdII Pincer Systems

Manen

Nakashima

Shinkai³

et al. 2000

Eur. J. Inorg. Chem.

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We have studied the coordination of substituted pyridines, and phosphorus‐ and sulfur‐containing ligands to an SCS PdII pincer system. These ligands coordinate to PdII (trans to the cyclopalladated aryl group) by quantitative substitution of the labile acetonitrile ligand in complex 1. Competition experiments showed that both electronic and steric effects influence the strength of coordination to the PdII pincer of the substituted pyridines. A quantitative analysis of the substituent effect was achieved by a Hammett correlation. Phosphorus‐containing ligands also coordinate to this SCS PdII motif, as evidenced by NMR spectroscopy and single‐crystal X‐ray diffraction studies. They are much stronger ligands than the pyridines. The coordination strength of the thioureas falls in between those of the pyridines and phosphanes/phosphites. Our results lead therefore to the following order of ligand strength towards PdII in SCS PdII pincers: PR3 > P(OR)3 > N,N′‐disubstituted thiourea > (substituted) pyridines > MeCN.

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Recent Findings in Cyclometallation of meta-Substituted Aryl Ligands by Platinum Group Metal Complexes by Caryl–R Bond Activation (R=H, CR3, SiR3)

Abstract: Transition metal complexes containing one or more metal ± aryl bonds are becoming increasingly important in catalysis.

Cited by 17 publications

References 16 publications

Synthesis and Structural Characterization of Lithium and Trimethyltin Complexes of 2,6-Bis(oxazolinyl)phenyl

Synthesis and Structural Characterization of Lithium and Trimethyltin Complexes of 2,6-Bis(oxazolinyl)phenyl

Inter- versus Intramolecular C−H Activation: Synthesis and Characterization of a Novel Platinum-Carbene Complex

Coordination Chemistry of SCS PdII Pincer Systems

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