Photochemistry of transition metal hydride complexes. 1. Photoinduced elimination of molecular hydrogen from chlorodihydrotris(triphenylphosphine)iridium and trihydrotris(triphenylphosphine)iridium

Geoffroy, Gregory L.; Pierantozzi, Ronald

doi:10.1021/ja00441a030

Cited by 68 publications

(29 citation statements)

References 2 publications

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“…These values are in a reasonable agreement with the experimental heat of the reaction, 15$20 kcal/mol [17]. These values are in a reasonable agreement with the experimental heat of the reaction, 15$20 kcal/mol [17].…”

Section: Thermal Processessupporting

confidence: 85%

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A theoretical study of the photochemical reductive elimination and thermal oxidative addition of molecular hydrogen from and to the Ir-complex

Hayashi

Nakai

Tokita

et al. 1998

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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The electronic mechanisms of the cyclic processes of photochemical reductive elimination of H 2 from [IrClH 2 (PH 3 ) 3 ] and thermal oxidative addition of H 2 to [IrCl(PH 3 ) 3 ] are investigated theoretically. The geometries of the ground and excited states are optimized using the Hartree-Fock and single excitation con®guration interaction methods, respectively, and higher level calculations for the ground and excited states are carried out by the symmetry adapted cluster (SAC)/SAC±con®guration interaction method. The present calculation shows that the reductive elimination of H 2 from [IrClH 2 (PH 3 ) 3 ] dose not occur thermally but photochemically through diabatic conversion from the lowest A¢ excited state to the ground state (A¢), while the oxidative addition of H 2 to [IrCl(PH 3 ) 3 ] easily proceeds thermally. The lowest 1 A¢ excited state involves the nature of the Ir-H 2 antibonding.

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Section: Thermal Processessupporting

confidence: 85%

“…In 1976, Georoy and Pierantozzi [17] reported that the irradiation of [IrClH 2 (PPh 3 ) 3 3 ] system oers a remarkable engine for hydrogen and energy storage. In 1976, Georoy and Pierantozzi [17] reported that the irradiation of [IrClH 2 (PPh 3 ) 3 3 ] system oers a remarkable engine for hydrogen and energy storage.…”

Section: Introductionmentioning

confidence: 99%

A theoretical study of the photochemical reductive elimination and thermal oxidative addition of molecular hydrogen from and to the Ir-complex

Hayashi

Nakai

Tokita

et al. 1998

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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“…That TEOA is a suitable donor but not €3,0 should therefore be ascribed not to thermodynamic, but to mechanistic reasons. The critical step in the sequence (39)- (42) is probably the deprotonation (40). Loss of the proton prevents reoxidation of reduced rhodium species by TEOA+ (38); furthermore, the neutral radical formed has reducing properties, making a second electron available (reaction (41)), a property which may explain the rapid generation of the Rh(1) species from Rh (bipy):+ (see reaction (53) below).…”

Section: R Tmentioning

confidence: 99%

Hydrogen Generation by Visible Light Irradiation of Aqueous Solutions of Metal Complexes. An approach to the photochemical conversion and storage of solar energy

Kirch¹,

Lehn²,

Sauvage³

1979

Helvetica Chimica Acta

555

338

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SummaryWe describe a photochemical system for the generation of hydrogen by water reduction under visible light or sunlight irradiation of aqueous solutions containing the following components: a photosensitizer, the Ru (bipy):+ complex, for visible light absorption; a relay species, the Rh (bipy):+ complex, which mediates water reduction by intermediate storage of electrons via a reduced state; an electron donor, triethanolamine (TEOA) which provides the electrons for the reduction process and a redox catalyst, colloidal platinum, which facilitates hydrogen formation. The conditions for efficient hydrogen production and the influence of the concentration of the components have been investigated; the metal complexes act as catalysts with high turnover numbers; excess bipyridine facilitates the reaction. The process contains two catalytic cycles: a ruthenium cycle and a rhodium cycle. The Ru cycle involves oxidative quenching of the "Ru (bipy)pexcited state by Rh (bipy):+ forming Ru (bipy):+ which is converted back to Ru (bipy):+ by oxidation of the electron donor TEOA, which is thus consumed. The Rh cycle comprises a complicated set of transformations of the initial Rh (bipy):+ complex. The reduced rhodium complex formed in the quenching process undergoes a series of transformations involving the Rh (bipy); complex and hydridorhodiumbipyridine species, from which hydrogen is generated by reaction with the protons of water. In view of the storage of two electrons in the reduced rhodium species, the process is formally a dielectronic water reduction. The properties and eventual participation of [Rh (111) (bi~y)~LL']"+ (L, L'= H20, OH-) species are investigated. It is concluded that at neutral pH in presence of excess bipyridine, the cycle involving regeneration of the Rh (bipy):+ complex is predominant. A number of experiments have been performed with modified systems. Hydrogen evolution is observed with other photosensitizers (like proflavin), other relay species (like Rh (dimethylbipy):+ or Co (11)-bipyridine complexes), other donor species, or 4 (1979) -Nr. 142 in absence of the platinum catalyst. It also occurs in absence (of photosensitizer by sunlight or UV. irradiation of Rh(bipy):+ or by visible light irradiation of iridium (111)-bipyridine complexes. These systems deserve further investigations. The present photochemical hydrogen generating system represents the reductive component of a complete water splitting process. Its role in solar energy conversion and in photochemical fuel production is discussed.

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“…In spite of the fact that both reactions were proven to occur separately, a cyclic catalytic process could not be obtained [108], probably because of an efficient side reaction between CH~CHO and the catalyst. More recently, it has D been found [109] that the reaction (H z clL H2 + (L = 2,2'-bipyridine or 1,10-phenanthroline) constitutes the photochemical step in the water-gas shift reaction CO + H20 ÷ CO 2 + H 2 R~CI(CO)L~.…”

Section: ~ + ~ (30)mentioning

confidence: 99%

Photocatalysis by transition-metal coordination compounds in homogeneous phase. Part II: Photochemical steps involving the organic substrate

Moggi

Juris

Sandrini

et al. 1984

Reviews of Chemical Intermediates

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Photochemistry of transition metal hydride complexes. 1. Photoinduced elimination of molecular hydrogen from chlorodihydrotris(triphenylphosphine)iridium and trihydrotris(triphenylphosphine)iridium

Cited by 68 publications

References 2 publications

A theoretical study of the photochemical reductive elimination and thermal oxidative addition of molecular hydrogen from and to the Ir-complex

A theoretical study of the photochemical reductive elimination and thermal oxidative addition of molecular hydrogen from and to the Ir-complex

Hydrogen Generation by Visible Light Irradiation of Aqueous Solutions of Metal Complexes. An approach to the photochemical conversion and storage of solar energy

Photocatalysis by transition-metal coordination compounds in homogeneous phase. Part II: Photochemical steps involving the organic substrate

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