Pentafluorophenylplatinum complexes containing η1- or η2-aryl–Pt interactions. Crystal structure of cis-[Pt(C6F5)2-({NC5H4[CH(η2-Ph)Ph]-2}-κN)]·0.5C6H5Me

Casas, José M.; Forniés, Juan; Martín, António; Menjón, Babil; Tomás, Milagros

doi:10.1039/dt9950002949

Cited by 13 publications

(3 citation statements)

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“…The Pt−C (2.27 and 2.25 Å) distances are comparable to other η 2 -arene adducts, ,− while the C11−C16 bond length of the coordinated p -xylene (1.45 Å) is slightly longer than for free p -xylene (1.39 Å) (Table ). The angle between the plane of the aromatic ring (defined by C11−C16−C15) and the Pt square-plane (defined by N31−Pt1−N21) is almost perpendicular (77.9°), as was seen in the benzene adduct (85.0°) …”

Section: Resultsmentioning

confidence: 62%

Barriers for Arene C−H Bond Activation in Platinum(II) η²-Arene Intermediates

et al. 2002

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Protonation of platinum(IV) complexes of the type Tp‘Pt(Ar)(H)(R) [Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate; Ar = aryl; R = H, C6H5] with [H(OEt2)2][BAr‘4] [BAr‘4 = tetrakis(3,5-trifluoromethylphenyl)borate] results in the formation of cationic platinum(II) η2-arene complexes [κ2-(HTp‘)Pt(η2-HAr)(R)][BAr‘4] [Ar = C6H5, R = H (2); Ar = MeC6H4, R = H (4); Ar = 3,6-Me2C6H3, R = H (6); Ar = R = C6H5 (8)]. A barrier of 9.4 kcal/mol for platinum migration around the η2-p-xylene ring was calculated for complex 6 at 183 K following variable-temperature NMR measurements. Eyring analysis of hydrogen exchange between the bound benzene and the hydride ligand for cationic benzene complex 2 indicates ΔH ⧧ = 11.7 ± 0.5 kcal mol-1 and ΔS ⧧ = −3.8 ± 2 cal mol-1 K-1. This process is assumed to proceed via arene C−H oxidative addition to give the five-coordinate platinum(IV) phenyl dihydride intermediate 2a. Isolation of ground state η2-arene adducts with adjacent hydride ligands has allowed the barrier to oxidative addition for arene C−H bonds (ΔG ⧧) to be measured as 13.3 kcal/mol for the p-hydrogen and 13.6 kcal/mol for the m-hydrogens in the toluene adduct 4 and 14.2 kcal/mol for the p-xylene adduct 6. Averaging of the environments for two Tp‘ arms is an NMR observable feature for the C 1 symmetric η2-benzene phenyl adduct 8. This dynamic process, which presumably occurs via a five-coordinate platinum(IV) diphenyl hydride intermediate 8a with C s symmetry, allows the barrier for arene C−H oxidative addition to be calculated as 12.9 kcal/mol. Kinetic isotope effects for oxidative addition of the arene C−H(D) bond in the benzene hydride adduct 2 and the benzene phenyl adduct 8 were determined to be k H/k D = 3.0 at 259 K and 4.7 at 241 K, respectively. These data provide insight into the energetics of arene C−H bond activation.

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Section: Resultsmentioning

confidence: 62%

Barriers for Arene C−H Bond Activation in Platinum(II) η²-Arene Intermediates

et al. 2002

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“…Keeping in mind that the compounds [{Pt(C∧P)(μ-Rpz)} 2 ] (Rpz = pz ( 2a ), 3,5-dmpz ( 2b ), 4-Mepz ( 2c )) react with [Ag(OClO 3 )(PPh 3 )] in a 1:2 molar ratio to afford the complexes [{Pt(C∧P)(μ-Rpz)} 2 Ag]ClO 4 (Rpz = pz ( 4a ), 3,5-dmpz ( 4b ), 4-Mepz ( 4c )), with [Ag(PPh 3 ) 2 ]ClO 4 as a byproduct, it is worth emphasizing the following. The strength of η 1 -arene− or η 2 -arene−metal interactions depends on the nature of both the arene and the complex fragment, but they are normally weak in nature, since this kind of interaction can be broken easily by weak donor ligands. − Surprisingly, in our case, the opposite holds, since the PPh 3 ligand is replaced from the coordination sphere of the Ag atom by the π electron density of two aromatic rings. As a result, this PPh 3 ligand bonds to another Ag atom to form [Ag(PPh 3 ) 2 ]ClO 4 as a byproduct.…”

Section: Resultsmentioning

confidence: 70%

Synthesis and Reactivity of the Neutral Pyrazolate Complexes [M₂{CH₂C₆H₄P(o-tolyl)₂-κC,P}₂(μ-Rpz)₂] (M = Pd, Pt; Rpz = Pz, 3,5-dmpz, 4-Mepz) toward AgClO₄. Molecular Structure of [Pt₂Ag{CH₂C₆H₄P(o-tolyl)₂-κC,P}₂(μ-4-Mepz)₂]ClO₄

et al. 2002

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The neutral compounds [Pt2{CH2C6H4P(o-tolyl)2-κC,P}2(μ-Rpz)2] (Rpz = pz (2a), 3,5-dmpz (2b), 4-Mepz (2c)) react with AgClO4 in a 1:1 molar ratio to give the trinuclear compounds [Pt2Ag{CH2C6H4P(o-tolyl)2-κC,P}2(μ-Rpz)2]ClO4 (Rpz = pz (4a), 3,5-dmpz (4b), 4-Mepz (4c)), which contain two Pt−Ag bonds. The reaction of [Pd2{CH2C6H4P(o-tolyl)2-κC,P}2(μ-3,5-dmpz)2] (3b) with AgClO4 renders [{Pd2(CH2C6H4P(o-tolyl)2-κC,P)2(μ3-3,5-dmpz-N,N ‘ ,C 4)2Ag(η2-μ2-ClO4)}2] (5), a palladium/silver compound with an unprecedented dmpz bridging ligand η1-bonded to the Ag centers, a coordination mode involving only the C4 atom of each dmpz ligand.

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“…The dihedral angle between the platinacycle and the benzene ring is 106.1°. There have been reports of platinum complexes displaying an intramolecular arene–platinum interaction, and their X-ray crystal structures have been determined, which are similar to the optimized structure of F . The identification of intermediate F also demonstrated the power of the NEB method.…”

Section: Resultsmentioning

confidence: 75%

Theoretical Probe to the Mechanism of Pt-Catalyzed C–H Acylation Reaction: Possible Pathways for the Acylation Reaction of a Platinacycle

et al. 2019

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Density functional theory (DFT) and nudged elastic band (NEB) theory have been used to study the possible pathways for the acylation of cycloplatinated complex A derived from 2-phenoxypyridine, which is conceived as the key step in the platinum-catalyzed acylation of 2-aryloxypyridines. Geometry optimization indicates that the previously proposed intermediate, an arenium ion species as a result of analogous aromatic substitution, is not an energy minimum, but rather cationic Pt-arene η 2 -complex E is obtained as a stable intermediate. NEB simulations suggest that the minimum energy pathway for the acylation reaction has energy barrier of 33.6 kcal/mol and consists of the following steps: (1) Nucleophilic substitution at acetyl chloride by the platinum of the reactant A forms five-coordinate Pt(IV) acylplatinum complex B with an energy barrier of 21.7 kcal/mol. (2) B undergoes 1,2-acyl migration from the platinum to the cyclometalated carbon through a three-membered platinacycle transition state to give Pt-arene η 2 -complex E with an energy barrier of 14.0 kcal/mol. (3) E undergoes ligand exchange with chloride to form neutral Pt-arene η 2 -complex F. (4) F undergoes ligand substitution with acetonitrile to give the product and the energy barrier is small (10.6 kcal/mol). The rate-determining step is the 1,2-acyl migration step. It is interesting to note that intermediate F was not included in the proposed mechanism but was identified by the NEB simulations. Five-coordinate Pt(IV) acylplatinum complex B undergoes barrierless ligand coordination with chloride to form neutral formal oxidative addition acylplatinum complex D; however, D is less stable than reactant A by 2.9 kcal/mol, which also implies that the isolation of an oxidative addition product Pt(IV) complex may be very challenging. The direct reductive elimination of D to form product P has a higher energy barrier (36.6 kcal/mol).

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Pentafluorophenylplatinum complexes containing η¹- or η²-aryl–Pt interactions. Crystal structure of cis-[Pt(C₆F₅)₂-({NC₅H₄[CH(η²-Ph)Ph]-2}-κN)]·0.5C₆H₅Me

Cited by 13 publications

References 53 publications

Barriers for Arene C−H Bond Activation in Platinum(II) η²-Arene Intermediates

Barriers for Arene C−H Bond Activation in Platinum(II) η²-Arene Intermediates

Synthesis and Reactivity of the Neutral Pyrazolate Complexes [M₂{CH₂C₆H₄P(o-tolyl)₂-κC,P}₂(μ-Rpz)₂] (M = Pd, Pt; Rpz = Pz, 3,5-dmpz, 4-Mepz) toward AgClO₄. Molecular Structure of [Pt₂Ag{CH₂C₆H₄P(o-tolyl)₂-κC,P}₂(μ-4-Mepz)₂]ClO₄

Theoretical Probe to the Mechanism of Pt-Catalyzed C–H Acylation Reaction: Possible Pathways for the Acylation Reaction of a Platinacycle

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Pentafluorophenylplatinum complexes containing η1- or η2-aryl–Pt interactions. Crystal structure of cis-[Pt(C6F5)2-({NC5H4[CH(η2-Ph)Ph]-2}-κN)]·0.5C6H5Me

Cited by 13 publications

References 53 publications

Barriers for Arene C−H Bond Activation in Platinum(II) η2-Arene Intermediates

Barriers for Arene C−H Bond Activation in Platinum(II) η2-Arene Intermediates

Synthesis and Reactivity of the Neutral Pyrazolate Complexes [M2{CH2C6H4P(o-tolyl)2-κC,P}2(μ-Rpz)2] (M = Pd, Pt; Rpz = Pz, 3,5-dmpz, 4-Mepz) toward AgClO4. Molecular Structure of [Pt2Ag{CH2C6H4P(o-tolyl)2-κC,P}2(μ-4-Mepz)2]ClO4

Theoretical Probe to the Mechanism of Pt-Catalyzed C–H Acylation Reaction: Possible Pathways for the Acylation Reaction of a Platinacycle

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Pentafluorophenylplatinum complexes containing η¹- or η²-aryl–Pt interactions. Crystal structure of cis-[Pt(C₆F₅)₂-({NC₅H₄[CH(η²-Ph)Ph]-2}-κN)]·0.5C₆H₅Me

Barriers for Arene C−H Bond Activation in Platinum(II) η²-Arene Intermediates

Barriers for Arene C−H Bond Activation in Platinum(II) η²-Arene Intermediates

Synthesis and Reactivity of the Neutral Pyrazolate Complexes [M₂{CH₂C₆H₄P(o-tolyl)₂-κC,P}₂(μ-Rpz)₂] (M = Pd, Pt; Rpz = Pz, 3,5-dmpz, 4-Mepz) toward AgClO₄. Molecular Structure of [Pt₂Ag{CH₂C₆H₄P(o-tolyl)₂-κC,P}₂(μ-4-Mepz)₂]ClO₄