Reactivity and mechanism in the ring-opening of cyclopropylmethylplatinum(IV) complexes

Abo-Amer, Anwar; Puddephatt, Richard J.

doi:10.1016/j.inoche.2010.09.044

Cited by 11 publications

(6 citation statements)

References 30 publications

(69 reference statements)

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“…The 1 H NMR spectrum of [(κ 3 -Tt Ph )Pt(CH 3 ) 3 ][OTf] ( 3a-L1 ) shows a single resonance at 9.4 ppm for the three triazolyl ring protons, indicating an ascent in symmetry to the C 3 v point group. The Pt–Me resonance moves downfield to 1.5 ppm and is consistent with other reported systems involving Pt(II)/Pt(IV) oxidations. ,− …”

Section: Resultssupporting

confidence: 90%

C–H and C–C Bond Formation Promoted by Facile κ³/κ² Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

Frauhiger¹,

White²,

Templeton³

2011

Organometallics

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A series of platinum complexes bearing 3-fold symmetrical “Click”-triazole-based scorpionate ligands (TtR) has been prepared. Metalation of these weakly donating ligands results in neutral Pt(II) complexes that display a κ2 coordination mode. Such complexes are susceptible to oxidative addition using a variety of electrophilic alkyl and allyl reagents to generate isolable cationic κ3 Pt(IV) complexes. Protonation of the κ2 precursors results in Pt(IV) dimethyl hydride cations. Thermolysis of the dimethyl hydride species at 35 °C in the presence of a trapping π-acid ligand initiates reductive elimination of methane and formation of a Pt(II) species of the type [TtPhPtMe(L)][BF4] (L  CO, ethylene, propylene, cis-2-butene, trans-2-butene, isobutylene) in good yield. Furthermore, the κ3 σ-allyl complexes [TtRPt(Ph)2(CH2CHCH2)][I] cleanly undergo Csp2–Csp2 reductive coupling to form biphenyl at ambient temperatures. The TtR ligand serves as a homofunctional hemilabile ligand and exhibits a lower barrier κ3/κ2 interconversion to generate reactive unsaturated five-coordinate complexes than the well-studied Tp′PtMe2H complex, which requires thermolysis at temperatures above 100 °C.

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Section: Resultssupporting

confidence: 90%

C–H and C–C Bond Formation Promoted by Facile κ³/κ² Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

Frauhiger¹,

White²,

Templeton³

2011

Organometallics

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“…Treating a methylene chloride solution of metallacycle 17 with methyl triflate at room temperature generated 18 , the methyl analogue of the hydride 10 (eq ). Metallacycle 18 exhibits a resonance in the 1 H NMR spectrum at 1.5 ppm with two-bond platinum coupling of 74 Hz, which is compatible with other reported Pt(IV) methyl complexes. ,− Allowing 18 to stand at room temperature overnight did not result in the appearance of a platinum hydride NMR signal. Note that C–C reductive elimination of the methyl group and C–H activation of the aryl would be expected to produce a Pt–H product.…”

Section: Resultssupporting

confidence: 85%

An Easy Conversion from Platinum(II) Reagents to Platinum(IV) Products: κ³ to κ² Coordination Mode Interconversion, Phenyl Migration, and Ortho C–H Activation Cascade in a Hemilabile “Click”-Triazole Scorpionate Platinum System

Frauhiger

Templeton

2012

Organometallics

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A series of platinum phenyl olefin complexes has been prepared that bear hemilabile “Click”-triazole based scorpionate ligands (TtR). Mild heating of the olefin adducts initiates a reaction sequence to form stable, cationic Pt(IV) hydride metallacycles. An attractive mechanism involves κ3/κ2 conversion, phenyl migration, and ortho C–H activation. Activation parameters for the overall C–C bond-forming and C–H bond-breaking process were obtained. Insertion products from mono- and disubstituted olefins reveal a kinetic preference for phenyl migration to the less sterically hindered olefin position but a thermodynamic preference for the β-substituted metallacycle isomer, in which steric bulk is further away from the metal center and the TtR ligand. Thermolysis converts the kinetically favored products to their thermodynamically stable isomers via a reversible C–C bond cleavage and formation reaction. EXSY NMR and deuterium-labeling studies reveal facile scrambling processes in the metallacycles due to the hemilabile ligand.

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“…The corresponding platinum(IV) methylcyclopropane complexes ( 103 – 104 ) were also prepared, but only complex 104 with coordinatively labile CF 3 CO 2 – anion undergoes ring-opening β-alkyl elimination (Scheme ). For complex 104 , β-alkyl elimination occurs at a significantly slower rate than the coordinatively unsaturated Pt II analogues, due to a large energetic penalty to create an open coordination site cis to the methylcyclopropyl ligand. In addition, an unfavorable electronic environment is created after β-alkyl elimination when two Pt–C occupy positions trans to each other.…”

Section: β-Alkyl Transfer Processes In Middle and Late Transition Met...mentioning

confidence: 99%

β-Alkyl Elimination: Fundamental Principles and Some Applications

2016

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This review describes organometallic compounds and materials that are capable of mediating a rarely encountered but fundamentally important reaction: β-alkyl elimination at the metal-Cα-Cβ-R moiety, in which an alkyl group attached to the Cβ atom is transferred to the metal or to a coordinated substrate. The objectives of this review are to provide a cohesive fundamental understanding of β-alkyl-elimination reactions and to highlight its applications in olefin polymerization, alkane hydrogenolysis, depolymerization of branched polymers, ring-opening polymerization of cycloalkanes, and other useful organic reactions. To provide a coherent understanding of the β-alkyl elimination reaction, special attention is given to conditions and strategies used to facilitate β-alkyl-elimination/transfer events in metal-catalyzed olefin polymerization, which provide the well-studied examples.

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Reactivity and mechanism in the ring-opening of cyclopropylmethylplatinum(IV) complexes

Cited by 11 publications

References 30 publications

C–H and C–C Bond Formation Promoted by Facile κ³/κ² Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

C–H and C–C Bond Formation Promoted by Facile κ³/κ² Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

An Easy Conversion from Platinum(II) Reagents to Platinum(IV) Products: κ³ to κ² Coordination Mode Interconversion, Phenyl Migration, and Ortho C–H Activation Cascade in a Hemilabile “Click”-Triazole Scorpionate Platinum System

β-Alkyl Elimination: Fundamental Principles and Some Applications

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Reactivity and mechanism in the ring-opening of cyclopropylmethylplatinum(IV) complexes

Cited by 11 publications

References 30 publications

C–H and C–C Bond Formation Promoted by Facile κ3/κ2 Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

C–H and C–C Bond Formation Promoted by Facile κ3/κ2 Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

An Easy Conversion from Platinum(II) Reagents to Platinum(IV) Products: κ3 to κ2 Coordination Mode Interconversion, Phenyl Migration, and Ortho C–H Activation Cascade in a Hemilabile “Click”-Triazole Scorpionate Platinum System

β-Alkyl Elimination: Fundamental Principles and Some Applications

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Resources

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C–H and C–C Bond Formation Promoted by Facile κ³/κ² Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

C–H and C–C Bond Formation Promoted by Facile κ³/κ² Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

An Easy Conversion from Platinum(II) Reagents to Platinum(IV) Products: κ³ to κ² Coordination Mode Interconversion, Phenyl Migration, and Ortho C–H Activation Cascade in a Hemilabile “Click”-Triazole Scorpionate Platinum System