Ultrafast reductive elimination of hydrogen from a metal carbonyl dihydride complex; a study by time-resolved IR and visible spectroscopy

Colombo, Mirco G.; George, Michael W.; Moore, John N.; Pattison, David I.; Perutz, Robin N.; Virrels, Ian G.; Ye, Tian-Qing

doi:10.1039/a704484d

Cited by 38 publications

(70 citation statements)

References 20 publications

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“…We have now studied a range of metal dihydride complexes by these techniques with nanosecond lasers in solution (ref. [11][12][13][14]. These experiments invariably show that reductive elimination is complete within the instrumental risetime of a few tens of nanoseconds.…”

Section: Studies Of Reductive Elimination By Time-resolved Spectroscopymentioning

confidence: 85%

“…The importance of these reactions lies in their application to C-H bond activation and, to a lesser extent, Si-H activation. [7][8][9][10][11][12][13][14]. These dihydride complexes do not undergo loss of hydrogen thermally.…”

Section: Introductionmentioning

confidence: 99%

“…1840 cm-1 (ref. 14). After an initial spike (due to the solvent response) during the instrumental risetime of ca.…”

Section: Studies Of Reductive Elimination By Time-resolved Spectroscopymentioning

confidence: 99%

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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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Section: Studies Of Reductive Elimination By Time-resolved Spectroscopymentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Metal dihydride complexes: Photochemical mechanisms for reductive elimination

Perutz¹

1998

Pure and Applied Chemistry

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“…Complex 1 (Scheme 1) has been characterized previously, 15,34 but a summary of its main spectroscopic features is provided in Scheme 1 and a 1 H NMR spectrum of the key hydride region is illustrated in Figure 1a; a 31 P{ 1 H} NMR spectrum is shown in the Supporting Information.…”

Section: ■ Resultsmentioning

confidence: 99%

“…5 In 1997, we identified 1 as an excellent target for investigating the photodissociation of H 2 by time-resolved UV/vis and timeresolved IR spectroscopy. 15 We observed a transient by both techniques that was assigned to [Ru(CO)(PPh 3 ) 3 ]a n d measured its rate of reaction with H 2 ((8.4 ± 0.4) × 10 7 dm 3 mol −1 cm −1 at room temperature). It was of particular importance that the transient exhibited a 95 cm −1 shift to low frequency in its CO-stretching band, providing proof of H 2 loss.…”

Section: ■ Introductionmentioning

confidence: 99%

Competing Pathways in the Photochemistry of Ru(H)₂(CO)(PPh₃)₃

et al. 2018

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Article:Procacci, Barbara orcid.org/0000-0001-7044-0560, Duckett, Simon B. orcid.org/0000-0002-9788-6615, George, Michael W. et al. (6 more and with pyridine on a nanosecond time scale. These two pathways, reductive elimination of H 2 and PPh 3 loss, are shown to occur with approximately equal quantum yields upon 355 nm irradiation. Low-temperature photolysis in the presence of H 2 reveals the formation of the dihydrogen complex Ru(H) 2 (η 2 -H 2 )(CO)(PPh 3 ) 2 , which is detected by NMR and IR spectroscopy. This complex reacts further within seconds at room temperature, and its behavior provides a rationale to explain the PHIP results. Furthermore, photolysis in the presence of AsPh 3 and H 2 generates Ru(H) 2 (AsPh 3 )(CO)(PPh 3 ) 2 . Two isomers of Ru(H) 2 (CO)(PPh 3 ) 2 (pyridine) are formed according to NMR spectroscopy on initial photolysis of 1 in the presence of pyridine under H 2 . Two further isomers are formed as minor products; the configuration of each isomer was identified by NMR spectroscopy. Laser pump-NMR probe spectroscopy was used to observe coherent oscillations in the magnetization of one of the isomers of the pyridine complex; the oscillation frequency corresponds to the difference in chemical shift between the hydride resonances. Pyridine substitution products were also detected by TRIR spectroscopy.

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Fast and Ultrafast Time‐Resolved Mid‐Infrared Spectrometry Using Lasers

Grills

George

2001

Handbook of Vibrational Spectroscopy

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The sections in this article are Introduction Fast TRIR Spectroscopy Fast TRIR Spectroscopy Using IR Lasers CW CO Lasers CW CO 2 Lasers Tunable IR Diode Lasers Color Center Lasers Difference Frequency Generation Ultrafast TRIR Studies Two‐Dimensional IR Spectroscopy Conclusions

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Ultrafast reductive elimination of hydrogen from a metal carbonyl dihydride complex; a study by time-resolved IR and visible spectroscopy

Cited by 38 publications

References 20 publications

Metal dihydride complexes: Photochemical mechanisms for reductive elimination

Metal dihydride complexes: Photochemical mechanisms for reductive elimination

Competing Pathways in the Photochemistry of Ru(H)₂(CO)(PPh₃)₃

Fast and Ultrafast Time‐Resolved Mid‐Infrared Spectrometry Using Lasers

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Ultrafast reductive elimination of hydrogen from a metal carbonyl dihydride complex; a study by time-resolved IR and visible spectroscopy

Cited by 38 publications

References 20 publications

Metal dihydride complexes: Photochemical mechanisms for reductive elimination

Metal dihydride complexes: Photochemical mechanisms for reductive elimination

Competing Pathways in the Photochemistry of Ru(H)2(CO)(PPh3)3

Fast and Ultrafast Time‐Resolved Mid‐Infrared Spectrometry Using Lasers

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Competing Pathways in the Photochemistry of Ru(H)₂(CO)(PPh₃)₃