Contrasting photochemical and thermal reactivity of Ru(CO)2(PPh3)(dppe) towards hydrogen rationalised by parahydrogen NMR and DFT studies

Damir Blazina; John P. Dunne; Stuart Aiken; Simon B. Duckett; Charlotte Elkington; John E. McGrady; Rinaldo Poli; Sue J. Walton; M. Sabieh Anwar; Jonathan A. Jones; Hilary A. Carteret

doi:10.1039/b510616h

Contrasting photochemical and thermal reactivity of Ru(CO)2(PPh3)(dppe) towards hydrogen rationalised by parahydrogen NMR and DFT studies

Damir Blazina, John P. Dunne, Stuart Aiken, Simon B. Duckett, Charlotte Elkington, John E. McGrady, Rinaldo Poli, Sue J. Walton, M. Sabieh Anwar, Jonathan A. Jones, Hilary A. Carteret

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Abstract

The synthesis, characterisation and thermal and photochemical reactivity of Ru(CO)₂(PPh₃)(dppe) 1 towards hydrogen are described. Compound 1 proved to exist in both fac (major) and mer forms in solution. Under thermal conditions, PPh₃ is lost from 1 in the major reaction pathway and the known complex Ru(CO)₂(dppe)(H)₂ 2 is formed. Photochemically, CO loss is the dominant process, leading to the alternative dihydride Ru(CO)(PPh₃)(dppe)(H)₂ 3. The major isomer of 3, viz. 3a, contains hydride ligands that are trans to CO and trans to one of the phosphorus atoms of the dppe ligand but a second isomer, 3b, where both hydride ligands are trans to distinct phosphines, is also formed. On the NMR timescale, no interconversion of 3a and 3b was observed, although hydride site interchange is evident with activation parameters of ΔH^‡ = 95 ± 6 kJ mol^-1 and ΔS^‡ = 26 ± 17 J K^-1 mol^-1. Density functional theory confirms that the observed species are the most stable isomeric forms, and suggests that hydride exchange occurs via a transition state featuring an η²- coordinated H₂ unit.

Original language	English
Pages (from-to)	2072-2080
Number of pages	9
Journal	Dalton Transactions
Volume	2006
Issue number	17
DOIs	https://doi.org/10.1039/b510616h
Publication status	Published - 2 Feb 2006
Externally published	Yes

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Blazina, D., Dunne, J. P., Aiken, S., Duckett, S. B., Elkington, C., McGrady, J. E., Poli, R., Walton, S. J., Anwar, M. S., Jones, J. A., & Carteret, H. A. (2006). Contrasting photochemical and thermal reactivity of Ru(CO)2(PPh3)(dppe) towards hydrogen rationalised by parahydrogen NMR and DFT studies. Dalton Transactions, 2006(17), 2072-2080. https://doi.org/10.1039/b510616h

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title = "Contrasting photochemical and thermal reactivity of Ru(CO)2(PPh3)(dppe) towards hydrogen rationalised by parahydrogen NMR and DFT studies",

abstract = "The synthesis, characterisation and thermal and photochemical reactivity of Ru(CO)2(PPh3)(dppe) 1 towards hydrogen are described. Compound 1 proved to exist in both fac (major) and mer forms in solution. Under thermal conditions, PPh3 is lost from 1 in the major reaction pathway and the known complex Ru(CO)2(dppe)(H)2 2 is formed. Photochemically, CO loss is the dominant process, leading to the alternative dihydride Ru(CO)(PPh3)(dppe)(H)2 3. The major isomer of 3, viz. 3a, contains hydride ligands that are trans to CO and trans to one of the phosphorus atoms of the dppe ligand but a second isomer, 3b, where both hydride ligands are trans to distinct phosphines, is also formed. On the NMR timescale, no interconversion of 3a and 3b was observed, although hydride site interchange is evident with activation parameters of ΔH‡ = 95 ± 6 kJ mol-1 and ΔS‡ = 26 ± 17 J K-1 mol-1. Density functional theory confirms that the observed species are the most stable isomeric forms, and suggests that hydride exchange occurs via a transition state featuring an η2- coordinated H2 unit.",

author = "Damir Blazina and Dunne, {John P.} and Stuart Aiken and Duckett, {Simon B.} and Charlotte Elkington and McGrady, {John E.} and Rinaldo Poli and Walton, {Sue J.} and Anwar, {M. Sabieh} and Jones, {Jonathan A.} and Carteret, {Hilary A.}",

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AU - Aiken, Stuart

AU - Duckett, Simon B.

AU - Elkington, Charlotte

AU - McGrady, John E.

AU - Poli, Rinaldo

AU - Walton, Sue J.

AU - Anwar, M. Sabieh

AU - Jones, Jonathan A.

AU - Carteret, Hilary A.

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N2 - The synthesis, characterisation and thermal and photochemical reactivity of Ru(CO)2(PPh3)(dppe) 1 towards hydrogen are described. Compound 1 proved to exist in both fac (major) and mer forms in solution. Under thermal conditions, PPh3 is lost from 1 in the major reaction pathway and the known complex Ru(CO)2(dppe)(H)2 2 is formed. Photochemically, CO loss is the dominant process, leading to the alternative dihydride Ru(CO)(PPh3)(dppe)(H)2 3. The major isomer of 3, viz. 3a, contains hydride ligands that are trans to CO and trans to one of the phosphorus atoms of the dppe ligand but a second isomer, 3b, where both hydride ligands are trans to distinct phosphines, is also formed. On the NMR timescale, no interconversion of 3a and 3b was observed, although hydride site interchange is evident with activation parameters of ΔH‡ = 95 ± 6 kJ mol-1 and ΔS‡ = 26 ± 17 J K-1 mol-1. Density functional theory confirms that the observed species are the most stable isomeric forms, and suggests that hydride exchange occurs via a transition state featuring an η2- coordinated H2 unit.

AB - The synthesis, characterisation and thermal and photochemical reactivity of Ru(CO)2(PPh3)(dppe) 1 towards hydrogen are described. Compound 1 proved to exist in both fac (major) and mer forms in solution. Under thermal conditions, PPh3 is lost from 1 in the major reaction pathway and the known complex Ru(CO)2(dppe)(H)2 2 is formed. Photochemically, CO loss is the dominant process, leading to the alternative dihydride Ru(CO)(PPh3)(dppe)(H)2 3. The major isomer of 3, viz. 3a, contains hydride ligands that are trans to CO and trans to one of the phosphorus atoms of the dppe ligand but a second isomer, 3b, where both hydride ligands are trans to distinct phosphines, is also formed. On the NMR timescale, no interconversion of 3a and 3b was observed, although hydride site interchange is evident with activation parameters of ΔH‡ = 95 ± 6 kJ mol-1 and ΔS‡ = 26 ± 17 J K-1 mol-1. Density functional theory confirms that the observed species are the most stable isomeric forms, and suggests that hydride exchange occurs via a transition state featuring an η2- coordinated H2 unit.

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Contrasting photochemical and thermal reactivity of Ru(CO)2(PPh3)(dppe) towards hydrogen rationalised by parahydrogen NMR and DFT studies

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