Laser-Induced Fluorescence of Molybdenocene and Tungstenocene in Low-Temperature Matrixes

Hill, Jeremy N.; Perutz, Robin N.; Rooney, A. Denise

doi:10.1021/j100002a015

Cited by 8 publications

(12 citation statements)

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“…Studies of the photochemistry of Cp 2 W(H) 2 in low-temperature matrices , confirmed the formation of the [Cp 2 W] fragment by H 2 photoinduced concerted elimination; [Cp 2 W] was characterized by IR and UV/vis absorption, laser-induced fluorescence, , and magnetic circular dichroism , (see section for details).…”

Section: Metal Hydride Photochemistry By Transition Metal Groupmentioning

confidence: 88%

“…Matrix isolation experiments revealed tungstenocene as the primary photoproduct and showed via IR, UV–vis, laser-induced fluorescence, and magnetic circular dichroism that it has a parallel sandwich structure with a 3 E 2g ground state. These early experiments are summarized in reviews. , Since then, the matrix photochemistry has been investigated in more detail. − Additional reports have added the photochemical reactions of Cp 2 W(H) 2 in solution with HSiCl 3 , HSiMe 2 Cl, and HSiMe 3 to make the corresponding Cp 2 WH(SiR 3 ) complexes. , Co-irradiation of Cp 2 W(H) 2 and metal–metal-bonded carbonyl complexes such as [CpNi(CO)] 2 or [CpRu(CO) 2 ] 2 have been used to generate heterodinuclear complexes. In these reactions with two metal complexes, there is no control of which complex undergoes photochemical reactions, and it is likely that both contribute .…”

Section: Photochemical Processesmentioning

confidence: 99%

“…The photoelimination of H 2 was described as concerted due to lack of detection of the HCO radical in CO matrices. , Photogeneration of the metallocene in matrices was exploited to generate the [Cp 2 Mo] fragment for optical determination of magnetization behavior; like [Cp 2 W], it has a triplet ground state . Molybdenocene exhibits an LMCT absorption (origin at 420 nm) and laser-induced fluorescence from the same electronic state. , UV–vis transient photochemistry agreed with the matrix investigations; a transient species was detected that decayed in ca. 10 μs by reaction with CO or the parent complex and was assigned to [Cp 2 Mo] …”

Section: Metal Hydride Photochemistry By Transition Metal Groupmentioning

confidence: 99%

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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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Section: Metal Hydride Photochemistry By Transition Metal Groupmentioning

confidence: 88%

Section: Photochemical Processesmentioning

confidence: 99%

Section: Metal Hydride Photochemistry By Transition Metal Groupmentioning

confidence: 99%

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Photochemistry of Transition Metal Hydrides

2016

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“…10-2 and 10-1 respectively (photolysis at 366 nm, ref 15). More recently, Belt et a1 exploited the knowledge of the extinction coefficient of the primary photoproduct of Ru to obtain a quantum yield for loss of hydrogen from Ru(drnpe)zHz of 0.85 k 0.05 via time-resolved spectroscopy (photolysis at 308 nm, ref 16). However, there is no knowledge of the variation of the quantum yield with wavelength of photolysis.…”

Section: Steady State Studies Of Photochehlical Elimination Of Hydrogenmentioning

confidence: 99%

Metal dihydride complexes: Photochemical mechanisms for reductive elimination

Perutz¹

1998

Pure and Applied Chemistry

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Most metal dihydride complexes with cis hydride ligands undergo photochemical reductive elimination of hydrogen. This class of reaction finds many applications as an entry point to highly reactive 16-electron intermediates which undergo C-H, Si-H or H-H activation. The 16-electron intermediates can often be characterised by matrix isolation methods at low temperature or by time-resolved spectroscopy in solution. The group 8 metal dihydrides of the types M ( d~n p e )~H~, (dmpe = Me2PCH2CH2PMe2, M = Fe, Ru, Os), and Ru(CO)(PPh&H2 have all been studied by time-resolved absorption spectroscopy in conjunction with product studies. In each case, the transient 16-electron species is formed by photochemical loss of H2 within the risetime of the apparatus. The complex Ru(CO)(PPh3)3H2 has also been studied by time-resolved IR spectroscopy which demonstrates the reduction in oxidation state via the COstretching frequency. Ultrafast spectroscopy of this complex with IR detection has been used to demonstrate that H2 elimination is complete within ca. 6 ps. Thus there is strong experimental evidence as well as theoretical arguments that the excited states of these complexes are dissociative with respect to loss of H2. INTRODUCTIONPhotolysis of many metal dihydride complexes of transition metals with mutually cis hydride ligands results in loss of molecular hydrogen. This reaction has provided one of the key entry points which allow access from 18-electron precursors to 16-electron intermediates capable of C-H bond activation. The photochemical reaction causes a reduction in oxidation state of two and is a typical example of reductive elimination. The reverse reaction will usually proceed thermally and is the prototype example of an oxidative addition reaction. The basic reaction is shown in Figure 1 together with examples of photo-active dihydride complexes. In this article, I will summarise advances in knowledge of their photochemical mechanisms.

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“…2,3 These unstable metallocenes were formed by UV photolysis of the corresponding (di)hydride precursors. Vibrationally resolved emission and excitation spectra were recorded for each complex with tunable pulsed laser irradiation.…”

Section: Introductionmentioning

confidence: 99%

Laser-Induced Fluorescence of Decamethylrhenocene in Low-Temperature Matrices

1996

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The emission and excitation spectra of decamethylrhenocene, Re(η 5 -C 5 Me 5 ) 2 have been recorded in argon and in nitrogen matrices with a tunable pulsed laser as exciting source. In argon matrices two sets of spectra may be excited selectively corresponding to different trapping sites or conformers of the guest molecules. Each set is dominated by a progression in ν 8 , a vibration corresponding to the in-phase combination of ringmetal-ring and ring-methyl bending modes (ν 8 ′ ) 392 (2) cm -1 ν 8 ′′ ) 383 (1) cm -1 ). Much weaker features can be detected corresponding to progressions involving the three other totally symmetric modes (ν x + nν 8 , x ) 6, 7, 9, n ) 0, 1, 2, ...). The emission and excitation bands in the principal site are symmetrical in shape with full width at half-maximum of only ca. 6 cm -1 . The spectra of Re(η 5 -C 5 Me 5 ) 2 in nitrogen matrices are similar to those in argon matrices, but differ in site/conformer structure. The excited state lifetime in nitrogen matrices has been determined by single photon counting methods to be 3.69 (7) ns. The quantum yield for emission in nitrogen matrices is estimated as 0.010.

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Laser-Induced Fluorescence of Molybdenocene and Tungstenocene in Low-Temperature Matrixes

Cited by 8 publications

References 5 publications

Photochemistry of Transition Metal Hydrides

Photochemistry of Transition Metal Hydrides

Metal dihydride complexes: Photochemical mechanisms for reductive elimination

Laser-Induced Fluorescence of Decamethylrhenocene in Low-Temperature Matrices

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