Unusual behavior in the 308 nm flash photolysis of Vaska's complex

Schultz, Richard H.

doi:10.1016/j.jorganchem.2003.08.033

Cited by 14 publications

(8 citation statements)

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“…Furthermore, in addition to the 100-μs process, a second component to the regeneration of I occurring over milliseconds can be seen in the trace shown in Figure . Regeneration of Vaska's complex following UV photolysis occurs on a millisecond time scale as well, , and we have previously presented evidence that it occurs via a dimeric intermediate . We see no evidence for any other carbonyl-containing species in our experiment, but given the relative amounts of “fast” and “slow” regeneration, it is not out of the question that a dimeric intermediate is present but at concentrations too low to provide a measurable (>∼10 -3 au) absorbance change.…”

Section: Resultssupporting

confidence: 64%

“…We felt that it is reasonable to hypothesize that this wavelength dependence might be due to the formation of different reaction intermediates, presumably due to excitation into different metal-to-ligand charge-transfer transitions that place different amounts of electron density on the different ligands , Given the known dependence of the photochemistry of complexes such as I on λ irr , we felt that it would be interesting to investigate the fast (μs) photochemistry of I when λ irr = 308 nm rather than 355 nm. …”

Section: Introductionmentioning

confidence: 99%

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Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe₃)₂

Krishnan

Schultz

2005

Inorg. Chem.

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Time-resolved infrared absorption spectroscopy is used to monitor the events during the first approximately 100 mus following 308-nm photolysis of trans-RhCl(CO)(PMe3)2 (I) in a C6D6 or Decalin solution. Upon photolysis, the intensity of the carbonyl stretching absorption of I decreases and a new C-O stretching absorption (A) appears at 2006 cm(-1) in C6D6 (2013 cm(-1) in Decalin). Within approximately 100 mus, A disappears concurrently with partial regeneration of I and oxidative addition of a solvent C-D (C-H) bond. Our observation of the prompt formation of a carbonyl-containing intermediate contrasts with prior observations that photolysis at longer wavelengths leads solely to dissociation of CO from I. The implications of the observation of A for the understanding of the mechanisms of photocatalytic reactions of I are discussed.

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Section: Resultssupporting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe₃)₂

Krishnan

Schultz

2005

Inorg. Chem.

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“…It was postulated that H 2 elimination would follow after the dissociation of those ligands . A more modern approach with time-resolved IR spectroscopy on IrCl(CO)(PPh 3 ) 2 did not support this interpretation, but there has been no reexamination of the dihydride complexes …”

Section: Metal Hydride Photochemistry By Transition Metal Groupmentioning

confidence: 96%

Photochemistry of Transition Metal Hydrides

2016

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Photochemical reactivity associated with metal-hydrogen bonds is widespread among metal hydride complexes and has played a critical part in opening up C-H bond activation. It has been exploited to design different types of photocatalytic reactions and to obtain NMR spectra of dilute solutions with a single pulse of an NMR spectrometer. Because photolysis can be performed on fast time scales and at low temperature, metal-hydride photochemistry has enabled determination of the molecular structure and rates of reaction of highly reactive intermediates. We identify five characteristic photoprocesses of metal monohydride complexes associated with the M-H bond, of which the most widespread are M-H homolysis and R-H reductive elimination. For metal dihydride complexes, the dominant photoprocess is reductive elimination of H2. Dihydrogen complexes typically lose H2 photochemically. The majority of photochemical reactions are likely to be dissociative, but hydride complexes may be designed with equilibrated excited states that undergo different photochemical reactions, including proton transfer or hydride transfer. The photochemical mechanisms of a few reactions have been analyzed by computational methods, including quantum dynamics. A section on specialist methods (time-resolved spectroscopy, matrix isolation, NMR, and computational methods) and a survey of transition metal hydride photochemistry organized by transition metal group complete the Review.

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“…The key feature of its photochemistry is transient loss of CO to form [IrCl(PPh 3 ) 2 ] which, with no substrate, rapidly reforms the original complex (8)(9)(10). There is evidence that the loss of CO actually occurs during the formation of a dimer following collision of an excited state complex with a ground state molecule (11). Geoffroy et al observed that irradiation of [IrCl(CO)(PPh 3 ) 2 ] yielded no permanent photoproducts (12), but Wink and Ford found that in chloroform, alone among several solvents tested, a permanent product did accumulate (10).…”

Section: Introductionmentioning

confidence: 99%

“…The key feature of its photochemistry is transient loss of CO to form [IrCl(PPh 3 ) 2 ] which, with no substrate, rapidly reforms the original complex (8–10). There is evidence that the loss of CO actually occurs during the formation of a dimer following collision of an excited state complex with a ground state molecule (11). Geoffroy et al.…”

Section: Introductionmentioning

confidence: 99%

The Photolysis of Chlorocarbonylbis(triphenylphosphine)iridium(I) in Chloroform

Witter

Karabulut

Hoggard³

2008

Photochem & Photobiology

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Under 254 or 313 nm irradiation in chloroform, [IrCl(CO)(PPh3)2] is converted cleanly to [IrCl2(CO)H(PPh3)2] through the addition of HCl, produced photochemically. Under 254 nm irradiation, some of the reaction of [IrCl(CO)(PPh3)2] occurs by direct photolysis of chloroform, though a greater contribution arises from a reaction initiated through absorption of light by the metal complex. Under 313 nm irradiation, essentially all of the reaction is metal-initiated. The linear dependence of the reaction rate on light intensity and on the fraction of light absorbed by the Ir(I) complex as well as the lack of a deuterium isotope effect rule out a radical process. Instead it is proposed that an association complex between excited state [IrCl(CO)(PPh3)2] and CHCl3 leads to dissociation of a chlorine atom from CHCl3, yielding HCl after abstraction of a hydrogen from another CHCl3. HCl then adds to a ground state [IrCl(CO)(PPh3)2] complex.

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Unusual behavior in the 308 nm flash photolysis of Vaska's complex

Cited by 14 publications

References 28 publications

Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe₃)₂

Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe₃)₂

Photochemistry of Transition Metal Hydrides

The Photolysis of Chlorocarbonylbis(triphenylphosphine)iridium(I) in Chloroform

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Unusual behavior in the 308 nm flash photolysis of Vaska's complex

Cited by 14 publications

References 28 publications

Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe3)2

Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe3)2

Photochemistry of Transition Metal Hydrides

The Photolysis of Chlorocarbonylbis(triphenylphosphine)iridium(I) in Chloroform

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Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe₃)₂

Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe₃)₂