Laser-induced fluorescence of reactive metallocenes (.eta.5-C5H5)2M (M = Re, W, Mo) and (.eta.5-C5Me5)2Re

Bell, Steven E. J.; Hill, Jeremy N.; McCamley, Andrew; Perutz, Robin N.

doi:10.1021/j100373a004

Cited by 11 publications

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“…For others, matrix photochemistry of metal hydrides is unique; it remains the only method of direct study. Examples include rhenocene ,, generated by photolysis of Cp 2 ReH and (H) 2 Mo(CH 2 ) generated by photolysis of the metal vapor product HMo(CH 3 ) (see section ). …”

Section: Specialist Photochemical Methods For Reactive Intermediates ...mentioning

confidence: 99%

“…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%

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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: Specialist Photochemical Methods For Reactive Intermediates ...mentioning

confidence: 99%

Section: Photochemical Processesmentioning

confidence: 99%

Photochemistry of Transition Metal Hydrides

2016

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“…The two principal sites may be excited selectively: site a, Aex = 477. 6 The intricate site structure is confirmed by variation of the excitation wavelength. In place of one major emission site as is seen in nitrogen, there are several in argon.…”

Section: Resultsmentioning

confidence: 89%

“…Some of this work has been published as preliminary communications. 6 Open-shell metallocenes with 16 and 17 valence electrons are not isolable for the second-and third-row transition metals but have been postulated as reaction intermediates in solution5 However, the neutral metallocenes of Mo, W, and Re may be studied by photolysis of the corresponding hydride complexes MCp2H" (M = Mo, W, = 2; M = Re, = l). 5 In previous work, we identified rhenocene in nitrogen and carbon monoxide matrices by a combination of IR, UV/vis absorption, and emission spectroscopies and magnetic circular dichroism.3 •7 We showed that it has a parallel sandwich structure with an it2)3-(ai)2 configuration, resulting in an orbitally degenerate, 2E2, ground state, as is also found for ferricenium and many other 17-electron metallocenes.…”

Section: Introductionmentioning

confidence: 99%

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Laser-Induced Fluorescence of Rhenocene in Low-Temperature Matrixes: Selective Excitation and Emission

Hill¹,

Perutz²,

Rooney³

1995

J. Phys. Chem.

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Rhenocene, Re(?75-C5H5)2, has been generated by photolysis of Ref^-CsHs^H isolated in nitrogen and argon matrices at 12 K, and has been studied by laser-induced fluorescence with a pulsed tunable laser. The emission lifetime of the lowest LMCT excited state is (71.9 ± 1.3) ns in nitrogen and (69.3 ± 1.4) ns in argon matrices.The emission and excitation spectra are far simpler and much better resolved than the UV/vis absorption spectrum, because the laser selects individual sites/conformers in the matrix (or groups of sites with very similar absorptions). Vibrational progressions are detected which are based on the ring-metal-ring stretching mode, v4, and combinations of that mode with the symmetric ring breathing mode, v2, and the symmetric C-H deformation mode, v3. In the LMCT excited state, there is an increase in v4 of 5% and a decrease in v3 (9%) and v2 (3%), consistent with transfer of an electron from a ligand jr-orbital to a metal-ligand bonding orbital.

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