Ground-State Guest-Host Chemistry in the Hydrophobic Cavity of the Unsaturated Cyclic Pd3(dppm)3CO2+ Cluster

Provencher, R.; Aye, Khin Than; Drouin, Marc; Gagnon, Jonathan; Boudreault, Nicolas; Harvey, Pierre D.

doi:10.1021/ic00095a012

Cited by 41 publications

(53 citation statements)

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“…by at least one order of magnitude on oing from CI-CH2Cl (0.25 M-I) to C6H5-CH2Cl (-7.3 M-' ) is not unprecedented. The K,, increases from acetate to benzoate, nitroethane to nitrobenzene, and acetonitrile to benzonitrile are also all around an order of magnitude (13). Cooperation between the binding of the C1 atom with the Pd, center, and the binding of the hydrophobic phenyl group and the cavity dppm-phenyl groups, appears to be responsible for this phenomenon.…”

Section: Binding Studiesmentioning

confidence: 89%

“…To establish the mechanistic step of the ~d~( d~~m )~~0~~ photoconversion to Pd(dppm)Cl,, the model system P~, (~~~~)~( C O ) ( Y )~+ (Y = N2C6H4NEt2) (13) was investigated. This compound is prepared from the binding of ~d~( d~~m )~~0~~ with [N,C6H4NEt2]+ (as the BFC salt) (13). This complex is surprisingly unstable to light in the presence of CH,Cl, to slowly form [Pd3(dppm)3(CO)(C1)]BF4 as identified by X-ray crystallography (as a CH,Cl, solvate).…”

Section: Photoreactions the ~~( D P P M )~~~~'mentioning

confidence: 99%

“…The cluster of choice is ~d , ( d~~m ) ,~0~+ since its absorption spectrum exhibits a well-defined absorption band at around 480 nm, where isosbestic points can be clearly observed upon association with a substrate (13). Methanol was chosen as solvent since previous studies established that this solvent interacts the least with the cavity (13), and offers good solubility for the cluster and substrates. Figure 1 shows UV-visible spectra changes upon addition of chloroform.…”

Section: Binding Studiesmentioning

confidence: 99%

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Photoinduced oxidative degradation of unsaturated M₃(dppm)₃CO²⁺ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Harvey¹,

Provencher²,

Gagnon³

et al. 1996

Can. J. Chem.

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Both ~, ( d~~r n ) ,~O~+ clusters (M = Pd, Pt) photoreact with chlorocarbons (Cl-R; R = CCl,, CHCl,, CH2C1, C6H5, ClOHl5 (adamant~l)) and chloride ion (slowly) to produce the oxidized mononuclear species M(dppm)Cl, as a sole isolated Mcoordinated inorganic product. Such reactions do not proceed in the dark, except for R = CH2C6H5. Among the organic products, the coupling compound R-R (R = C6H5) is observed along with many phosphine compounds such as P(C6H5),. In an attempt to elucidate the photoinduced mechanism at the early stage of the phototransformations, the following have been investigated : the ground state binding constants (K,, for M = Pd in methanol), the photochemical quantum yields of cluster disappearance (Qdis for M = Pd) as a function of substrates, substrate concentrations, excitation wavelengths, solvents (ethanol vs toluene), and presence of CO, and the emission lifetimes (7, for M = Pt) at 77 K as a function of substrate concentrations (CH,Cl, and CHCI,) in ethanol and toluene. Some of the experimental conclusions have also been corroborated theoretically using density functional theory. Geometry optimization calculations have been performed for the model compounds P~,(PH,)~co~+-.c~-, Pd3(PH3)62+, P~, ( P H , )~C~~+ . C~~, P~,(PH,)~CO~+~-CI-CH,, and P~,(PH,)~co~+ in their ground states.Key words: atom abstraction, photochemistry, C-C1 bond, clusters, host-guest.RCsumC : Les agrCgats ~, ( d~~r n ) ,~0~+ (M = Pd, Pt) photorkagissent tous les deux avec les chlorocarbones (Cl-R; CCI,, CHCl,, CH2C1, C6H5, ClOHl6 (adamantyle)) et avec l'ion chlorure (lentement) pour conduire B des espkces mononuclCaires oxydCes M(dppm)Cl, qui correspondent au seul produit inorganique M-coordinC B Ctre isole. Ces reactions ne se produisent pas B la noirceur, except6 pour le composC R = CH2C6H5. Parmi les composCs organiques, on observe le composC de couplage R-R (R = C6H5) ainsi que plusieurs phosphines telle que la P(C6H5),. Dans le but d'Clucider le mCcanisme photoinduit dans 1'Ctape initiale des phototransfonnations, on a examink les caractCristiques suivantes : les constantes d'association dans 1'Ctat fondamental (K,,, pour M = Pd dans le methanol), les rendements quantiques photochimiques pour la disparition des agrCgats (Qdis pour M = Pd) en fonction des substrats, des concentrations de substrat, des longueurs d'onde d'excitation, des solvants (Cthanol vs. tolukne) et de la presence de CO et les durCes de vie d'Cmissions (7, pour M = Pt), B 77 K, en fonction des concentrations de substrat (

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Section: Binding Studiesmentioning

confidence: 89%

Section: Photoreactions the ~~( D P P M )~~~~'mentioning

confidence: 99%

Section: Binding Studiesmentioning

confidence: 99%

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Photoinduced oxidative degradation of unsaturated M₃(dppm)₃CO²⁺ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Harvey¹,

Provencher²,

Gagnon³

et al. 1996

Can. J. Chem.

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“…This was verified by CPK models using computer modelings (SYBYL 5.5; Triphos Associates, St-Louis, Mo.) of the crystal structure of [Pd3(dppm),CO](CF3C02)(PF6) (27), in which the cavity is emptied from its CF3C02-substrate, and replaced by 0, sitting on one of the Pd atoms. The presence of a sharp and unique singlet in the ,'P-( H ) -HNMR ( 4 .…”

Section: Photoadditionmentioning

confidence: 89%

“…The weak solvent dependence on T, is associated with the ~d~( d~~m )~~~~+ -s o l v e n t guest-host chemistry (27). Because the diffusion rate constants typically range between lo9 and 10'' M-' s-' for common organic solvents (the data are taken from ref.…”

Section: Picosecond Flash Photolysismentioning

confidence: 99%

Photoinduced addition of dioxygen molecules in the unsaturated sites of the Pd₃(dppm)₃CO²⁺ catalyst

Harvey¹,

Crozet²,

Aye³

1995

Can. J. Chem.

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The photoinduced addition of 0, onto the unsaturated cluster Pd,(dppm),C~~+ (as a CF,CO,-salt) in acetonitrile is reported. The final product ~d , ( d~~m ) , ( O , )~ (~( 0 , ) = 838 and 866 cm-') is formed in a multistep fashion in which two photochemical intermediates are observed (presumably ~d,(dppm),(0,)(~0)~+ and ~d , ( d~~m ) , ( 0 , )~+ ) .No X-ray structure could be obtained, but numerous spectroscopic findings demonstrate that 0, binds the Pd, center as a peroxo-02, and acts as a two-electron donor that triply bridges the metal atoms (forming a 44-electron cluster). The very small excited state lifetimes (between 25 and 35 ? 10 ps) obtained by picosecond flash photolysis indicate that the primary photoreaction is unimolecular, and demonstrate that the first photochemically added 0, molecule must be preassembled in the excited state prior to any photoinduced transformation. This ~d , ( d~~m ) , C 0~+ . . . 0 , ground state complex is responsible for the photoinduced production of the bisdioxygen compound and can be observed by UV-visible spectroscopy. The low efficiency of the photoreaction (quantum yield (0) = 0.033 ? 0.004) is explained by the very short excited state lifetime at 298 K, and the competition of 0, with solvent molecules to occupy the unsaturated site of the empty cavity in ~d , ( d~~m ) ,~0~+ (i.e., ground state guest-host chemistry). The binding constant for 0, with ~d , ( d~~m ) ,~0~+ is roughly estimated to range between 1 and 730 M-I in the ground state and is considered to be weak.

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Synthesis and Reactivity of Tripalladium Clusters

Kovala‐Demertzi¹

1999

Metal Clusters in Chemistry

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Ground-State Guest-Host Chemistry in the Hydrophobic Cavity of the Unsaturated Cyclic Pd3(dppm)3CO2+ Cluster

Cited by 41 publications

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Photoinduced oxidative degradation of unsaturated M₃(dppm)₃CO²⁺ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Photoinduced oxidative degradation of unsaturated M₃(dppm)₃CO²⁺ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Photoinduced addition of dioxygen molecules in the unsaturated sites of the Pd₃(dppm)₃CO²⁺ catalyst

Synthesis and Reactivity of Tripalladium Clusters

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Ground-State Guest-Host Chemistry in the Hydrophobic Cavity of the Unsaturated Cyclic Pd3(dppm)3CO2+ Cluster

Cited by 41 publications

References 0 publications

Photoinduced oxidative degradation of unsaturated M3(dppm)3CO2+ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Photoinduced oxidative degradation of unsaturated M3(dppm)3CO2+ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Photoinduced addition of dioxygen molecules in the unsaturated sites of the Pd3(dppm)3CO2+ catalyst

Synthesis and Reactivity of Tripalladium Clusters

Contact Info

Product

Resources

About

Photoinduced oxidative degradation of unsaturated M₃(dppm)₃CO²⁺ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Photoinduced oxidative degradation of unsaturated M₃(dppm)₃CO²⁺ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Photoinduced addition of dioxygen molecules in the unsaturated sites of the Pd₃(dppm)₃CO²⁺ catalyst