Computational study of C-C activation of 1,3-dimesitylimidazol-2-ylidene (IMes) at ruthenium: The role of Ligand bulk in accessing reactive intermediates

Richard A. Diggle; Stuart A. Macgregor; Michael K. Whittlesey

doi:10.1021/om700977f

Computational study of C-C activation of 1,3-dimesitylimidazol-2-ylidene (IMes) at ruthenium: The role of Ligand bulk in accessing reactive intermediates

Richard A. Diggle, Stuart A. Macgregor, Michael K. Whittlesey

School of Engineering & Physical Sciences

Research output: Contribution to journal › Article › peer-review

38 Citations (Scopus)

Abstract

Density functional theory calculations have been employed to model phosphine substitution in Ru(PPh₃)₃(CO)(H)₂ to form Ru(IMes)(PPh₃)₂(CO)(H)₂ (1_mono) and Ru(IMeS)₂(PPh₃)(CO)(H)₂ (1_bis), as well as the novel C(aryl)-C(sp³) intramolecular bond activation of the IMes ligand in 1_bis. The computed ligand exchange energies show that 1_bis, is unstable with respect to displacement of IMes by PPh₃ and will thus re-form 1_mono over time. PPh ₃/IMes substitution also leads to a significant labilization of the PPh₃ ligand trans to hydride, a result of increasing steric encumbrance upon the introduction of the bulky IMes ligands. The energetics of intramolecular C-C and C-H activation have been computed for both 16e Ru(IMes)_n(PPh₃)_3-n(CO) and 14e Ru(IMes) _n(PPh₃)_2-n(CO) species (n = 1 or 2) and indicate that the introduction of a second IMes ligand does not significantly promote the actual C-C activation step. Instead the need to have two IMes ligands present in the metal coordination sphere before C-C activation can occur is linked to the promotion of PPh₃ loss in 1_bis, which makes the formation of unsaturated species such as Ru(IMeS)₂(CO) particularly accessible. © 2008 American Chemical Society.

Original language	English
Pages (from-to)	617-625
Number of pages	9
Journal	Organometallics
Volume	27
Issue number	4
DOIs	https://doi.org/10.1021/om700977f
Publication status	Published - 25 Feb 2008

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title = "Computational study of C-C activation of 1,3-dimesitylimidazol-2-ylidene (IMes) at ruthenium: The role of Ligand bulk in accessing reactive intermediates",

abstract = "Density functional theory calculations have been employed to model phosphine substitution in Ru(PPh3)3(CO)(H)2 to form Ru(IMes)(PPh3)2(CO)(H)2 (1mono) and Ru(IMeS)2(PPh3)(CO)(H)2 (1bis), as well as the novel C(aryl)-C(sp3) intramolecular bond activation of the IMes ligand in 1bis. The computed ligand exchange energies show that 1bis, is unstable with respect to displacement of IMes by PPh3 and will thus re-form 1mono over time. PPh 3/IMes substitution also leads to a significant labilization of the PPh3 ligand trans to hydride, a result of increasing steric encumbrance upon the introduction of the bulky IMes ligands. The energetics of intramolecular C-C and C-H activation have been computed for both 16e Ru(IMes)n(PPh3)3-n(CO) and 14e Ru(IMes) n(PPh3)2-n(CO) species (n = 1 or 2) and indicate that the introduction of a second IMes ligand does not significantly promote the actual C-C activation step. Instead the need to have two IMes ligands present in the metal coordination sphere before C-C activation can occur is linked to the promotion of PPh3 loss in 1bis, which makes the formation of unsaturated species such as Ru(IMeS)2(CO) particularly accessible. {\textcopyright} 2008 American Chemical Society.",

author = "Diggle, {Richard A.} and Macgregor, {Stuart A.} and Whittlesey, {Michael K.}",

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AU - Macgregor, Stuart A.

AU - Whittlesey, Michael K.

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N2 - Density functional theory calculations have been employed to model phosphine substitution in Ru(PPh3)3(CO)(H)2 to form Ru(IMes)(PPh3)2(CO)(H)2 (1mono) and Ru(IMeS)2(PPh3)(CO)(H)2 (1bis), as well as the novel C(aryl)-C(sp3) intramolecular bond activation of the IMes ligand in 1bis. The computed ligand exchange energies show that 1bis, is unstable with respect to displacement of IMes by PPh3 and will thus re-form 1mono over time. PPh 3/IMes substitution also leads to a significant labilization of the PPh3 ligand trans to hydride, a result of increasing steric encumbrance upon the introduction of the bulky IMes ligands. The energetics of intramolecular C-C and C-H activation have been computed for both 16e Ru(IMes)n(PPh3)3-n(CO) and 14e Ru(IMes) n(PPh3)2-n(CO) species (n = 1 or 2) and indicate that the introduction of a second IMes ligand does not significantly promote the actual C-C activation step. Instead the need to have two IMes ligands present in the metal coordination sphere before C-C activation can occur is linked to the promotion of PPh3 loss in 1bis, which makes the formation of unsaturated species such as Ru(IMeS)2(CO) particularly accessible. © 2008 American Chemical Society.

AB - Density functional theory calculations have been employed to model phosphine substitution in Ru(PPh3)3(CO)(H)2 to form Ru(IMes)(PPh3)2(CO)(H)2 (1mono) and Ru(IMeS)2(PPh3)(CO)(H)2 (1bis), as well as the novel C(aryl)-C(sp3) intramolecular bond activation of the IMes ligand in 1bis. The computed ligand exchange energies show that 1bis, is unstable with respect to displacement of IMes by PPh3 and will thus re-form 1mono over time. PPh 3/IMes substitution also leads to a significant labilization of the PPh3 ligand trans to hydride, a result of increasing steric encumbrance upon the introduction of the bulky IMes ligands. The energetics of intramolecular C-C and C-H activation have been computed for both 16e Ru(IMes)n(PPh3)3-n(CO) and 14e Ru(IMes) n(PPh3)2-n(CO) species (n = 1 or 2) and indicate that the introduction of a second IMes ligand does not significantly promote the actual C-C activation step. Instead the need to have two IMes ligands present in the metal coordination sphere before C-C activation can occur is linked to the promotion of PPh3 loss in 1bis, which makes the formation of unsaturated species such as Ru(IMeS)2(CO) particularly accessible. © 2008 American Chemical Society.

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Computational study of C-C activation of 1,3-dimesitylimidazol-2-ylidene (IMes) at ruthenium: The role of Ligand bulk in accessing reactive intermediates

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