Contrasting Photochemical and Thermal Catalysis by Ruthenium Arsine Complexes Revealed by Parahydrogen Enhanced NMR Spectroscopy

Ralph W. Adams, Richard O. John, Damir Blazina, Beatriz Eguillor, Martin C.R. Cockett, John P. Dunne, Joaquín López-Serrano, Simon B. Duckett*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The thermal and photochemical reactivity of Ru(CO)3(dpae) (1) and Ru(CO)2(dpae)(PPh3) (2) towards H2 and diphenylacetylene is described. These reactions are monitored by NMR spectroscopy in conjunction with the parahydrogen induced polarisation (PHIP) effect, spatially resolved chemical shift imaging and the Only Parahydrogen Spectroscopy (OPSY) signal filtering method. The results are supported by DFT. The thermal and photochemical reactions of 1 with H2 proceed by CO loss and form Ru(H)2(CO)2(dpae) (3). 1 catalyses the formation of 1,2 diphenylethane, cis- and trans-stilbene, and 1,2,3,4 tetraphenylbutadiene under 325 nm irradiation at 295 K in a reaction where Ru(CO)2(dpae)(η2-CHPh=CPhCPh=CHPh) forms. When the same reaction is monitored under thermal conditions at 333 K the η2-diene complex is no longer detected but hydride containing Ru(CHPhCH2Ph)(H)(CO)2(dpae) and Ru(CO)2(dpae)(trans-stilbene) are seen. For 1, the photochemical promotion of hydrogenation through 325 nm irradiation results in an approximate 5.5-fold increase in turnover at 333 K when compared to no irradiation. In contrast, 2 reacts thermally with H2 at 295 K through PPh3 and CO loss with both Ru(H)2(CO)(dpae)(solvent) and 3 being detected. Under irradiation, CO loss dominates and two isomers of Ru(H)2(CO)(dpae)(PPh3) form. While 2 forms the same 4 organic products at 295 K and a second isomer of Ru(CHPhCH2Ph)(H)(CO)2(dpae) alongside the diene complex no photochemical promotion of hydrogenation is observed.

Original languageEnglish
Article number202100991R1
Number of pages11
Issue number5
Early online date12 Jan 2022
Publication statusPublished - 8 Feb 2022

Bibliographical note

Funding Information:
We are grateful to the EPSRC and the European Union (HYDROCHEM network, contract HPRN‐CT‐2002‐00176) for part funding. Financial support from the Spanish MEC (Project Consolider ORFEO (CSD 2007‐00006)) is also acknowledged. We thank Prof. R. N. Perutz, the late Dr. R. J. Mawby and Dr. J. M. Lynam for helpful discussions. Experimental assistance from Dr. N. J. Smith, Dr. N. J. Wood, Dr. S. Aiken, Dr. J. A. Aguilar, Dr. K. A. M. Ampt and Mrs S. J. Walton is gratefully acknowledged.

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